Soil sampling requirements in United States

National rules: 40 CFR Part 412, Concentrated Animal Feeding Operations Point Source Category. By state: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, Wisconsin and Wyoming.

Soil sampling rules in United States, with the exact wording of each source
Country / region	Purpose / programme	Time / frequency	Area per sample	Method	Depth	Cores	Status and source
United States
United StatesFederal rule in every state. State rules below may add to it.	Phosphorus soil analysis for manure applicationFederal CAFO effluent guidelines, nutrient management plan	Repeat Soil phosphorus at least once every 5 years. Manure nitrogen and phosphorus at least once a year.	Not specified	Not specified	Not specified	Not specified	Conditional40 CFR § 412.4 (govinfo, 2025 edition)
Who it applies to, the exact wording and every source Who it applies to Concentrated animal feeding operations that land-apply manure, litter or process wastewater, at or above these sizes: 700 mature dairy cows; 1,000 other cattle or veal calves; 2,500 swine of 55 lb or more, or 10,000 smaller swine; 55,000 turkeys; 30,000 laying hens or broilers with a liquid manure system; 82,000 laying hens or 125,000 other chickens with another manure system. Outside the rule Operations below those sizes, and any operation that does not land-apply manure, litter or process wastewater. In force from Under review Legal text 40 CFR Part 412, Concentrated Animal Feeding Operations Point Source Category, § 412.4(c)(3), with § 412.30 and § 412.40 The wording in the source Timing Manure must be analyzed a minimum of once annually for nitrogen and phosphorus content, and soil analyzed a minimum of once every five years for phosphorus content. § 412.4(c)(3), Manure and soil sampling Who it applies to This section applies to any CAFO subject to subpart C of this part (Dairy and Beef Cattle other than Veal Calves) or subpart D of this part (Swine, Poultry, and Veal Calves). § 412.4(a) Each CAFO subject to this section that land applies manure, litter, or process wastewater, must do so in accordance with the following practices § 412.4(c) Outside the rule This subpart does not apply to such CAFOs with less than the following capacities: 700 mature dairy cows whether milked or dry; 1,000 cattle other than mature dairy cows or veal calves. § 412.30 This subpart does not apply to such CAFOs with less than the following capacities: 2,500 swine each weighing 55 lbs. or more; 10,000 swine each weighing less than 55 lbs.; 30,000 laying hens or broilers if the facility uses a liquid manure handling system; 82,000 laying hens if the facility uses other than a liquid manure handling system; 125,000 chickens other than laying hens if the facility uses other than a liquid manure handling system; 55,000 turkeys; and 1,000 veal calves. § 412.40 Sources 40 CFR § 412.4 (govinfo, 2025 edition) Law 40 CFR § 412.30, applicability Law 40 CFR § 412.40, applicability Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
AlabamaUnited StatesAlabama only. Other states set their own rules.	Soil tests on fields that receive animal wasteADEM animal feeding operation rules (AFO and CAFO)	Repeat At a frequency that meets NRCS technical standards and guidelines, and as often as needed to protect groundwater and surface water	Not specified	Accepted standard soil sampling procedures, on each field.	0 to 3 inches in sod crops. Depth of the plow layer in cultivated crops.	Not specified	ConditionalAla. Admin. Code ch. 335-6-7 (Alabama Legislative Services Agency)
Who it applies to, the exact wording and every source Who it applies to Animal feeding operations in Alabama, for each field where animal waste or wastewater has been or will be land applied. Laboratory and analysis Methods in the Southern Region soil test bulletins (Southern Cooperative Service Bulletins 289 and 374), the Alabama crop soil test recommendations (Auburn Series No. 178), or another method the Director approves. Analyses include pH and lime requirement, extractable phosphorus, and extractable zinc, copper, arsenic and other selected metals where the qualified credentialed professional finds them probable at high levels. In force from Under review Legal text Alabama Administrative Code, Chapter 335-6-7 (ADEM, animal feeding operations), Rule 335-6-7-.26(5) and Rule 335-6-7-.03 The wording in the source Timing Soil samples shall be collected and analyzed at a frequency that meets NRCS technical standards and guidelines, and as often as is necessary to ensure protection of groundwater and surface water quality. Rule 335-6-7-.26(5)(b) Method shall be sampled according to accepted standard soil sampling procedures. Rule 335-6-7-.26(5) Depth The surface soils (0-3 inches in sod crops and depth of plow layer in cultivated crops) of each field where waste/wastewater has been or will be land applied shall be sampled according to accepted standard soil sampling procedures. Rule 335-6-7-.26(5) Who it applies to of each field where waste/wastewater has been or will be land applied Rule 335-6-7-.26(5) the requirements of this Chapter are applicable to all new and existing AFOs in the State. Rule 335-6-7-.03(2) Laboratory and analysis Soil pH and lime requirement for the soil and crop to be grown. Rule 335-6-7-.26(5)(b)1 Extractable phosphorus. Rule 335-6-7-.26(5)(b)2 Soil Test Methods for the Southern Region of the United States, 1983, Southern Cooperative Service Bulletin, 289, University of Georgia, Athens, Georgia Rule 335-6-7-.26(5)(a) Other analytical methodology(s) as may be approved by the Director or his designee. Rule 335-6-7-.26(5)(a)3 Reference Soil and Media Diagnostic Procedures for the Southern Region of the United States, 1992, S.J. Donahue (ed.), Southern Cooperative Service Bulletin 374 Rule 335-6-7-.26(5)(a)1 Soil Test Fertilizer Recommendations For Alabama Crops, 1994, J.F. Adams, C.C. Mitchell, and H.H. Bryant, Agronomy And Soils Department Series No. 178 (as amended), Auburn University Rule 335-6-7-.26(5)(a)2 Extractable zinc, copper, arsenic, and other selected metals, if it is determined by the QCP that it is probable that one or more metals … present in sufficiently high concentrations in the land applied waste or wastewater, or naturally present in the soil Rule 335-6-7-.26(5)(b)3 Sources Ala. Admin. Code ch. 335-6-7 (Alabama Legislative Services Agency) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
AlabamaUnited StatesAlabama only. Other states set their own rules.	Grid and zone sampling for lime and fertilizerAlabama Cooperative Extension System, precision soil sampling advice	Repeat Grid sampling every 4 to 5 years, with zone sampling in between	Grids of 2.5 acres or less. Up to 5 acres in relatively uniform fields. Zones of 10 acres or less.	Grid sampling to set a baseline in new or problem fields, then management zones. Hand sampling: cores in a circle around the grid center. Automated samplers: an S pattern through the grid. A zigzag through each zone.	Not specified	Eight to twelve cores per grid or zone sample. At least ten to fifteen for zones of 10 acres or less, more for larger zones.	Official guidanceACES ANR-3181, Precision Soil Sampling Strategies for Site-Specific Nutrient Management
Who it applies to, the exact wording and every source Who it applies to Advice for Alabama fields from the Alabama Cooperative Extension System (Auburn University and Alabama A and M). Not law. In force from Under review Legal text ACES ANR-3181, Precision Soil Sampling Strategies for Site-Specific Nutrient Management (2025) The wording in the source Timing Ideally, grid sampling should be conducted every 4 to 5 years in each field, while zone sampling should be used in between to be more effective with both nutrient applications and sampling costs. ANR-3181, Summary Area per sample The size of sampling grids can range between 1 and 5 acres, but a smaller grid size of 2.5 acres or less is recommended to accurately capture variability in soil pH and nutrient levels within fields. Larger grid sizes (up to 5 acres) are often used in relatively uniform fields to reduce labor and sampling costs. ANR-3181, Grid Sampling sampling grids should be 2.5 acres or less for grid sampling, and management zones should be 10 acres or less for zone sampling. ANR-3181, Summary Method grid sampling should be used in all newly cropped fields; in fields that have been brought back into production after a few years; in fields with past management issues; or in any field where a baseline of nutrient variability needs to be established. ANR-3181, Choice of Precision Soil Sampling Strategy point sampling is usually the preferred method, where eight to ten soil cores are collected in a circular pattern (in a radius of 30 to 50 feet depending on grid size) around the centroid point within a grid. ANR-3181, Grid Sampling an S pattern (or Z pattern) is more common when soil samples are collected using an automated soil sampler mounted on a utility terrain vehicle (UTV). ANR-3181, Grid Sampling one of the most common techniques is to follow a zigzag travel pattern through the zone, randomly collecting soil cores at regular intervals ANR-3181, Zone Sampling Cores an adequate number of soil cores (eight to twelve) should be collected within each grid or zone to make a composite sample. ANR-3181, Summary at least ten to fifteen cores should be collected for zones of 10 acres or less and the number of soil cores should be increased accordingly for zones larger than 10 acres. ANR-3181, Zone Sampling Sources ACES ANR-3181, Precision Soil Sampling Strategies for Site-Specific Nutrient Management Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
AlaskaUnited StatesAlaska only. Other states set their own rules.	Routine soil fertility samplingUniversity of Alaska Fairbanks Cooperative Extension Service, soil sampling instructions	Not specified	Not specified	At least 13 points per sample, following the form diagram. On contour strips, 6 cores 20 feet in from the edge of the strip and 6 from the opposite side. Separate samples where soil type, past fertilizer or lime, or cropping history differ.	Tilling or plowing depth on cultivated land, or 6 inches. Pastures 3 or 4 inches.	At least 13 slices or borings per sample	Official guidanceUAF Cooperative Extension Service, Kenai soil test interpretation form 2019 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Alaska fields, pastures and gardens from the University of Alaska Fairbanks Cooperative Extension Service. Not law. In force from Under review Legal text UAF Cooperative Extension Service, Kenai soil test interpretation form (2019), Soil Sampling Instructions The wording in the source Method Follow the diagram below to properly locate the samples. For sloping land (contour strips), take 6 samples 20 feet in from the edge of the entire strip and 6 samples from the opposite side of the strip. Soil Sampling Instructions If the field, pasture, or garden varies in soil type, previous fertilizer or lime application, or cropping history, sample each area separately for best results and interpretation. Soil Sampling Instructions Rectangular pasture, field, turf, or garden plot showing 13 points of collection to obtain one representative soil sample. Figure 1 caption Depth Sample down to the tilling or plowing depth on cultivated lands or to a depth of 6 inches. In pastures, you need only sample to a depth of 3 or 4 inches. Soil Sampling Instructions Cores obtain thin slices or borings of soil from at least 13 places in a given area. Soil Sampling Instructions, Vegetables, Small Fruit, Home Gardens, Fields, and Pastures Sources UAF Cooperative Extension Service, Kenai soil test interpretation form 2019 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ArizonaUnited StatesArizona only. Other states set their own rules.	Soil sampling for commercial crop productionUniversity of Arizona Cooperative Extension, soil sampling guide	Repeat Regularly, if not every season, before planting each crop	Whole field sampling: one composite sample per 15 to 20 acres	Whole field: random cores in a zigzag across the field. Grid: composites per grid cell or points at grid intersections. Zone: separate composites where variation is already known.	12 inches for vegetables such as lettuce, spinach, broccoli, celery or cantaloupes. 24 inches for cotton, alfalfa, corn or wheat. Tilled soils to tillage depth.	15 to 20 cores or scoops per site, depending on field size and the laboratory	Official guidanceUniversity of Arizona Cooperative Extension AZ2147 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for commercial agriculture in Arizona from the University of Arizona Cooperative Extension. Not law. In force from Under review Legal text University of Arizona Cooperative Extension AZ2147, A Guide to Effective Soil Sampling for Sustainable Crop Production (July 2025) The wording in the source Timing Growers managing agricultural lands are encouraged to test their soils regularly, if not every season, before planting each crop. AZ2147, Introduction Area per sample As a rule of thumb, one composite sample should be collected per 15-20 acres of area. AZ2147, Types of Sampling Procedures, 1. Whole Field Sampling Method Samples are collected randomly in a zigzag pattern across the field without consideration of any management practices or topographic features. AZ2147, 1. Whole Field Sampling Grid sampling (Figure 4) is a type of spatial sampling that involves dividing the whole field into uniform grids. AZ2147, 2. Grid Sampling The first method is done by collecting composite samples in the individual grid, which provides information about the area. The second method of grid sampling is done by collecting soil samples at the points created by the overlapping lines. AZ2147, 2. Grid Sampling Zone sampling (Figure 5) is used when points of variation across a field are already known. AZ2147, 3. Zone Sampling Depth For example, if the crop is a vegetable such as romaine or iceberg lettuce, spinach, broccoli, celery, or cantaloupes, a 12-inch sampling depth is adequate; however, for crops like cotton, alfalfa, corn or wheat, a 24-inch sampling depth is recommended. AZ2147, Composite Sampling For example, tilled soils only need to be taken to the depth that tilling has occurred. AZ2147, Composite Sampling Cores In general, 15 to 20 soil samples (cores or scoops) (Figure 2) are collected per site (or plot), depending on the size of the field and the requirements of the laboratory doing the testing. AZ2147, Composite Sampling Sources University of Arizona Cooperative Extension AZ2147 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ArkansasUnited StatesArkansas only, and within the designated nutrient surplus areas. Other states set their own rules.	Soil test before phosphorus fertilizer and in nutrient management plansArkansas Soil Nutrient and Poultry Litter Application and Management Program (nutrient surplus areas)	Result valid Soil tests in a nutrient management plan or poultry litter management plan: not more than 5 years old	Not specified	Not specified	Not specified	Not specified	ConditionalANRC Title 22 (PDF, Arkansas Department of Agriculture)
Who it applies to, the exact wording and every source Who it applies to Land in a designated nutrient surplus area. A soil test is required before commercial fertilizer containing phosphorus is applied at the protective rate. Nutrient management plans and poultry litter management plans must carry soil tests not more than five years old. Outside the rule Commercial fertilizer with nitrogen but no phosphorus may be applied without a soil test. In force from 1 January 2010 Legal text Arkansas Natural Resources Commission Title 22, Rules Governing the Arkansas Soil Nutrient and Poultry Litter Application and Management Program, Sections 2202.3, 2202.5, 2203.3 and 2204.2 The wording in the source Timing Soil tests – not more than five years old. Section 2203.3 B.5.a (nutrient management plan, actual activity records); same text at Section 2204.2 B.6.a (poultry litter management plan) Who it applies to A soil test is required before applying commercial fertilizers containing phosphorus at the protective rate. Section 2202.5 B After a soil test with nutrient application recommendations is obtained for lands within a nutrient surplus area, a person may apply commercial fertilizer in compliance with the protective rate. Section 2202.3 A.2 no person shall apply nutrients to soils or associated crops within a nutrient surplus area unless nutrients are applied in compliance with a nutrient management plan or a poultry litter management plan prepared by a certified nutrient planner or at the protective rate for commercial fertilizers set forth in Section 2202.5. Section 2202.3 A Outside the rule Commercial fertilizer containing nitrogen but not phosphorus may be applied without a soil test. Section 2202.5 B In force (effective January 1, 2010) Title page, Title 22 Sources ANRC Title 22 (PDF, Arkansas Department of Agriculture) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ArkansasUnited StatesArkansas only. Other states set their own rules.	Routine soil fertility samplingUniversity of Arkansas System Division of Agriculture Cooperative Extension, soil test advice	Result valid A test guides fertilizer for 3 or 4 years. Resample when tests are over 4 years old. Repeat Consider sampling yearly under intensive management or with several crops a year	Not specified	Zigzag pattern preferred. Sample each field or management unit separately.	Crop fields to plowing depth, usually 4 to 6 inches. Pastures about 4 inches.	At least 12 random points per area	Official guidanceUniversity of Arkansas Cooperative Extension FSA2121 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Arkansas fields, pastures, lawns and gardens from the University of Arkansas System Division of Agriculture. Not law. In force from Under review Legal text University of Arkansas Cooperative Extension FSA2121, Test Your Soil for Plant Food and Lime Needs (September 2026) The wording in the source Timing Your soil tests can serve as a guide for fertilizer practices for the next three or four years. If you have tests over four years old, take samples again for up-to-date recommendations. If using intensive management or producing several crops per year, consider sampling yearly. FSA2121, page 2 Method A zigzag sampling pattern is preferred (Figure 3). FSA2121, procedure step 2 Sample each field or management unit separately. FSA2121, page 1 Depth Sample crop fields to the depth of plowing, usually 4 – 6 inches (Figure 4). Take samples in pastures, gardens, lawns, around shrubs and golf courses to a depth of about 4 inches FSA2121, procedure step 3 Cores Take soil with a soil probe or shovel from at least 12 random points in each area to obtain a representative sample. FSA2121, procedure step 2 Sources University of Arkansas Cooperative Extension FSA2121 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
CaliforniaUnited StatesCalifornia, Central Valley Region only: existing milk cow dairies under Order R5-2013-0122. Other regions and states set their own rules.	Soil phosphorus monitoring on dairy land application areasCentral Valley Water Board, Dairy General Order (waste discharge requirements for existing milk cow dairies)	Repeat Once every 5 years from each land application area. May be spread over 5 years by sampling 20 percent of the areas each year.	Not specified	Not specified	Not specified	Not specified	ConditionalCentral Valley Water Board Order R5-2013-0122 with Monitoring and Reporting Program (PDF)
Who it applies to, the exact wording and every source Who it applies to Existing milk cow dairies in the Central Valley Region covered by the General Order, on each land application area. Laboratory and analysis Laboratory analysis for soluble phosphorus. Spring and fall pre-plant nitrate, organic matter and other tests at 0 to 1 foot and 1 to 2 feet are recommended but not required. In force from Under review Legal text Central Valley Regional Water Quality Control Board Order R5-2013-0122, Reissued Waste Discharge Requirements General Order for Existing Milk Cow Dairies, Monitoring and Reporting Program, Table 2 (Nutrient Monitoring, Soil) The wording in the source Timing Once every 5 years from each land application area (may be distributed over a 5-year period by sampling 20% of the land application areas annually): MRP, Table 2 Nutrient Monitoring, Soil Who it applies to REISSUED WASTE DISCHARGE REQUIREMENTS GENERAL ORDER FOR EXISTING MILK COW DAIRIES Order title page all Dischargers specified by the Central Valley Water Board and all Dischargers that were formerly regulated under the original version of Order R5-2007-0035 adopted in May 2007, their agents, successors, and assigns shall comply with the following: Order, operative paragraph after Finding 44 Laboratory and analysis Laboratory analyses for soluble phosphorus MRP, Table 2 Nutrient Monitoring, Soil The following soil tests are recommended but not required: MRP, Table 2 Nutrient Monitoring, Soil Sources Central Valley Water Board Order R5-2013-0122 with Monitoring and Reporting Program (PDF) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
CaliforniaUnited StatesCalifornia only. Other states set their own rules.	General fertility and nitrate samplingUniversity of California Cooperative Extension, guidelines for soil sampling	Repeat General fertility: every 3 years is common Season Spring or fall, at the same time each year, not after fertilizer Repeat Nitrate-N: every year, preplant or before fertilization	Not specified	W-shaped pattern, a zigzag across the whole block, or a diagonal line. Divide non-uniform fields into blocks by cropping history and varieties, observed differences in crop development, and soil series.	General fertility: 6 inches or tilling depth. Nitrate-N: 6 inches to 3 feet, by rooting depth and leaching risk.	At least 20 cores per block	Official guidanceUCCE, Guidelines for Soil Sampling (PDF, UC ANR)
Who it applies to, the exact wording and every source Who it applies to Advice for California growers from University of California Cooperative Extension (UC Agriculture and Natural Resources). Not law. In force from Under review Legal text UC Cooperative Extension (Small Farms Advisor, Yolo, Solano and Sacramento Counties), Guidelines for Soil Sampling The wording in the source Timing Frequency: every 3 years is common, best to do before crops with high demands ( ex. Tomatoes have a high K demand), between the same crops in crop rotation For general fertility testing Best to do in the spring or fall For general fertility testing Do not sample after fertilizer has been added For general fertility testing Conduct samples the same time year after year For general fertility testing Frequency: every year; preplant, before fertilization or both For Nitrate-N testing Method Sample in a W-shaped pattern, by walking a zigzag course across the entire block, or walking a diagonal line Principles, Representative Divide non-uniform fields into blocks, based on Principles, Uniformity Cropping history, varieties Principles, Uniformity, first bullet Observed differences in crop development yield Principles, Uniformity, second bullet Differences in soil series (SoilWeb Ap) Principles, Uniformity, third bullet Depth Sampling depth should be 6” or the tilling depth For general fertility testing Depth: 6” to 3’, depending on the rooting depth and risk of leaching between sampling and phase of high crop uptake For Nitrate-N testing Cores Take a minimum of 20 cores for the block, which are mixed in 1 clean bucket, from which a single subsample is removed for lab testing Protocol, Taking a soil sample Sources UCCE, Guidelines for Soil Sampling (PDF, UC ANR) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ColoradoUnited StatesColorado only. Other states set their own rules.	Soil tests on land that receives CAFO manure or wastewaterColorado Animal Feeding Operations Control Regulation (Regulation No. 81), facility management plan for non-permitted CAFOs	Repeat At least once a year for available nutrients, including nitrate-nitrogen Repeat Top one foot for available phosphorus at least once every 5 years, or as section 81.6(2)(b)(v) sets for phosphorus transport risk reassessments	Not specified	Not specified	Top one foot for the available phosphorus test. No depth set for the annual test.	Not specified	Conditional5 CCR 1002-81, official PDF, Colorado Secretary of State (version effective 31 July 2017)
Who it applies to, the exact wording and every source Who it applies to Operators of non-permitted CAFOs in Colorado, on land application sites for manure and wastewater, as part of the facility management plan. Laboratory and analysis Available nutrients including nitrate-nitrogen every year; available phosphorus every five years. Results are used to set manure and wastewater application rates. In force from Under review Legal text 5 CCR 1002-81, Regulation No. 81, Animal Feeding Operations Control Regulation (Water Quality Control Commission), Section 81.6(2)(a)(ii) The wording in the source Timing The soil of land application sites shall be sampled and analyzed a minimum of once annually for available nutrients, including nitrate-nitrogen. 81.6(2)(a)(ii)(B) The top one foot of soil of land application sites shall be sampled and analyzed for available phosphorus a minimum of once every five years, or as specified in section 81.6(2)(b)(v), below. 81.6(2)(a)(ii)(C) Depth The top one foot of soil of land application sites shall be sampled and analyzed for available phosphorus 81.6(2)(a)(ii)(C) Who it applies to The operator of a non-permitted CAFO shall compile and maintain on-site a facility management plan (FMP) that includes, to the extent applicable, the information specified in sections 81.6(1), 81.6(2), 81.6(3) and 81.6(4). 81.6, opening The operator of a non-permitted CAFO shall develop, document in the FMP and implement the following practices and procedures for land application sites by no later than February 27, 2009 or upon being defined as a CAFO. 81.6(2) Laboratory and analysis Manure, wastewater, and soil shall be sampled and analyzed with the following frequency. The results of the analyses shall be used in determining application rates for manure and wastewater. 81.6(2)(a)(ii) a minimum of once annually for available nutrients, including nitrate-nitrogen. 81.6(2)(a)(ii)(B) Sources 5 CCR 1002-81, official PDF, Colorado Secretary of State (version effective 31 July 2017) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ColoradoUnited StatesColorado only. Other states set their own rules.	Routine soil fertility samplingColorado State University Soil, Water and Plant Testing Laboratory, soil sampling instructions	Not specified	Not specified	Systematic or random sampling pattern. Separate samples for areas that differ in crop growth, soil color, or fertilizer and amendment history.	Agricultural fields 0 to 8 inches	10 to 15 subsamples per composite sample	Official guidanceCSU Soil, Water and Plant Testing Laboratory, Soil Sampling Instructions (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Colorado fields, gardens and lawns from the Colorado State University soil testing laboratory, distributed through CSU Extension offices. Not law. In force from Under review Legal text Colorado State University Soil, Water and Plant Testing Laboratory, Soil Sampling Instructions (March 2026) The wording in the source Method Use either a systematic or random sampling pattern to collect soil samples (Figure 2). Sample Collection Submit a separate soil sample for any area that differs in crop growth, soil color, or fertilizer and amendment history. Sample Collection Depth Collect 10 to 15 subsamples from the soil surface to a depth of 8 inches (0–8"). Sample Collection, Agricultural fields Cores Collect 10 to 15 subsamples from the soil surface to a depth of 8 inches (0–8"). Sample Collection, Agricultural fields Sources CSU Soil, Water and Plant Testing Laboratory, Soil Sampling Instructions (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ConnecticutUnited StatesConnecticut only. Other states set their own rules.	Soil phosphorus test on Large CAFO land application fieldsConnecticut DEEP General Permit for Concentrated Animal Feeding Operations (CAFO GP)	Repeat Soil analyzed for phosphorus at least once every 5 years	Not specified	Not specified	Not specified	Not specified	ConditionalConnecticut DEEP, CAFO General Permit DEEP-WPED-GP-030 (PDF)
Who it applies to, the exact wording and every source Who it applies to Large CAFOs registered under the Connecticut CAFO General Permit (DEEP-WPED-GP-030) that land apply manure, litter, digestate or agricultural wastewater. Laboratory and analysis Phosphorus content. Results are used to set manure, litter, digestate and wastewater application rates. In force from 1 January 2023 Legal text Connecticut DEEP General Permit for Concentrated Animal Feeding Operations, DEEP-WPED-GP-030, issued under section 22a-430b of the Connecticut General Statutes, Section 5(f)(1)(A) The wording in the source Timing Manure must be analyzed a minimum of once annually for nitrogen and phosphorus content, and soil analyzed a minimum of once every five years for phosphorus content. The results of these analyses are to be used in determining application rates for manure, litter, digestate and other agricultural wastewater. Section 5(f)(1)(A), Manure and soil sampling Who it applies to Each Large CAFO that land applies manure, litter, digestate or agriculture wastewater must do so in accordance with the following practices: Section 5(f)(1), Additional Requirement for Large CAFOs Laboratory and analysis soil analyzed a minimum of once every five years for phosphorus content. Section 5(f)(1)(A) In force Effective Date: January 1, 2023 Expiration Date: December 31, 2027 Cover page Sources Connecticut DEEP, CAFO General Permit DEEP-WPED-GP-030 (PDF) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
ConnecticutUnited StatesConnecticut only. Other states set their own rules.	Routine soil fertility samplingUniversity of Connecticut Soil Nutrient Analysis Laboratory, soil nutrient sampling instructions	Season Any time the ground is not frozen. Fall is highly recommended.	No sample may represent more than 15 acres	12 or more random, evenly distributed spots. Separate samples for areas that differ in topography, drainage, texture, crop growth or use, soil color, or fertilizer history.	Crop field 6 to 8 inches or the plough layer depth. Grass 3 to 4 inches.	12 or more cores or slices per sample	Official guidanceUConn Plant and Soil Health Center, Sampling Instructions
Who it applies to, the exact wording and every source Who it applies to Advice for Connecticut farms, gardens and lawns from the University of Connecticut soil testing laboratory. Not law. In force from Under review Legal text UConn George Leigh Minor Plant and Soil Health Center, Soil Nutrient Sampling Instructions The wording in the source Timing Samples may be collected any time of year the ground is not frozen. The waiting period for results is longest in April and May. Testing the soil in the fall is highly recommended. When and How to Sample Area per sample Under no circumstances should samples represent areas larger than 15 acres. Soil Nutrient Sampling Instructions, When and How to Sample Method Submit a separate sample for areas differing in topography, drainage, soil texture, with different crop growth or intended crop usage, soil color, or fertilizer/amendment history. When and How to Sample Depth Crop field: 6 to 8 inches or the plough layer depth Sample Collection, depths Grass – 3 to 4 inches, Sample Collection, depths Cores collect cores or thin slices of soil from 12 or more random, evenly distributed spots (sampling points) in your sample area Sample Collection Sources UConn Plant and Soil Health Center, Sampling Instructions Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
DelawareUnited StatesDelaware only. Other states set their own rules.	Soil test results in the nutrient management planDelaware Nutrient Management Program (Delaware Nutrient Management Commission)	Not specified	Not specified	Not specified	Not specified	Not specified	ConditionalDelaware Code Title 3 (PDF), Chapter 22
Who it applies to, the exact wording and every source Who it applies to Animal feeding operations over 8 animal units, and anyone who owns, leases or controls more than 10 acres where nutrients are applied. Their nutrient management plan must include the results of applicable soil analyses, and records of implementation must include soil test results. The plan is updated at least every 3 years or on significant changes in operations; the Act sets no soil sampling interval. Outside the rule Nutrient handlers applying to turf of more than 1/4 acre but less than 10 acres need no plan, but stay subject to the limits in the title and the regulations. Animal feeding operations that use no other nutrients and do not land apply their animal waste may substitute an animal waste management plan. County, municipal and industrial facilities permitted by DNREC under the land treatment of wastes rules are exempt from the chapter. Laboratory and analysis Phosphorus is read as the Mehlich 3 fertility index value (FIV). Fields above FIV 499 need a phosphorus site index assessment before phosphorus is applied. In force from Under review Legal text Delaware Code, Title 3, Chapter 22 (Nutrient Management), § 2247 (nutrient management plans) and § 2202 (definitions) The wording in the source Who it applies to All animal feeding operations with greater than 8 animal units or any person who owns, leases or otherwise controls property totaling more than 10 acres upon which nutrients are applied shall develop and implement a nutrient management plan in accordance with the schedule outlined in this section. § 2247(a) Results of applicable soil, plant, water, manure, or organic by-products analyses. § 2247(a)(4), plan contents Soil test results and recommended nutrient application rates; § 2247(d)(1), records of implementation Nutrient management plans shall be updated a minimum of every 3 years or upon significant alterations in facility operations, or upon a 25% or greater increase in facility operations. § 2247(e) Outside the rule Nutrient handlers who apply nutrients to turf totaling more than ¼ acres (10,890 square feet) but less than 10 acres shall not be required to have a nutrient management plan but are subject to limits outlined in this title and the Commission’s regulations. § 2247(a) In the case of animal feeding operations where no other nutrients are used for farming and the animal waste is not land-applied, the operator of the facility may substitute an animal waste management plan for a nutrient management plan. § 2247(j) County, municipal and industrial facilities discharging solid or liquid waste and permitted by the Department of Natural Resources and Environmental Control under The Guidance and Regulations Governing the Land Treatment of Wastes shall be exempt from the provisions of this chapter. § 2247(l) Laboratory and analysis “Fertility index value” or “FIV” is equivalent to the measured Mehlich 3 soil test phosphorus concentration in parts per million § 2202(13) All fields with FIV exceeding 499 must have a PSI assessment prior to phosphorus application. Results of the PSI are valid for a term not to exceed 3 years. § 2247(b)(2) Sources Delaware Code Title 3 (PDF), Chapter 22 Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
DelawareUnited StatesDelaware only. Other states set their own rules.	Soil sampling and analysis for nutrient management plansDelaware Nutrient Management Program, Delaware Conservation Practice Standard: Soil Sampling and Analysis	Not specified	No more than 40 acres per sample	Smaller areas that differ in color, texture, drainage class, management or productivity are sampled separately.	Approximately 8 inches	A minimum of 15 to 25 cores per sample	Official guidanceDelaware Department of Agriculture, Practice Standard Soil Sampling and Analysis (PDF)
Who it applies to, the exact wording and every source Who it applies to Practice standard of the Delaware Nutrient Management Program, applying among other cases as part of any nutrient management plan. Published as a program standard, not as law. Laboratory and analysis Laboratories enrolled each year in a proficiency assessment program such as NAPT or ALP. Results in ppm or University of Delaware Fertility Index Value. In force from Under review Legal text Delaware Department of Agriculture, Delaware Conservation Practice Standard, Soil Sampling and Analysis (October 2016) The wording in the source Area per sample A soil sample should represent an area no larger than 40 acres Considerations Method Smaller areas that seem different in color, texture, drainage class, management practices, and/or productivity should be sampled separately. Considerations Depth a minimum of 15 to 25 soil cores taken approximately eight inches deep. Considerations Cores a minimum of 15 to 25 soil cores taken approximately eight inches deep. Considerations Laboratory and analysis Soils should be tested only by labs that have enrolled as participants of a proficiency assessment program (such as North American Proficiency Testing (NAPT) or Agriculture Laboratory Proficiency (ALP) each year. Criteria, Proficiency Testing All lab results should be reported in parts per million (ppm) or University of Delaware, Fertility Index Value (UD-FIV) Criteria, Proficiency Testing Sources Delaware Department of Agriculture, Practice Standard Soil Sampling and Analysis (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
DelawareUnited StatesDelaware only. Other states set their own rules.	Soil sampling for commercial crop productionUniversity of Delaware Cooperative Extension, Delaware Soil Testing Program	Repeat Annual crops: every year, or every 2 to 3 years where fertility is very high Repeat Perennial crops such as alfalfa or pasture: before seeding, then at least every 3 years	In general, 40 acres at most per sample	One soil type or condition per sample. Separate samples for different soils or management histories. Avoid wet spots, dead furrows, stockpile sites and old fertilizer bands.	Plow depth, usually 6 to 9 inches. No-till and reduced tillage also 6 to 9 inches.	15 to 25 cores per sample	Official guidanceUniversity of Delaware Soil Testing Program, General Information
Who it applies to, the exact wording and every source Who it applies to Advice for commercial crop production in Delaware from University of Delaware Cooperative Extension. Not law. In force from Under review Legal text University of Delaware Soil Testing Program, How to Take a Soil Sample for Commercial Crop Production The wording in the source Timing Annual Crops: Testing annually is generally recommended. If fertility levels are very high, sampling every 2 to 3 years is adequate. When and How Often to Test Perennial Crops (e.g., Alfalfa/Pasture): Test prior to seeding and at least every 3 years thereafter. When and How Often to Test Area per sample Maximum Size: In general, 40 acres is the maximum area that should be represented by a single sample. How to Take a Soil Sample for Commercial Crop Production, Sampling Guidelines Method Separate Samples: Areas with different soil types (e.g., Sandy Knoll vs. Black Soil) or different management histories (e.g., Corn field vs. Soybean field) must be sampled separately. Sampling Guidelines A good soil sample should represent only one soil type or condition. Selecting the Sampling Area Depth Standard Depth: Soil samples are generally taken to the plow depth, usually 6 to 9 inches from the surface. Proper Sampling Techniques, 1. Depth No-till/Reduced-tillage: These should also be sampled to the 6 to 9-inch depth for fertilizer recommendations. Proper Sampling Techniques, 1. Depth Cores Composite Sampling: Each individual sample should consist of 15 to 25 "cores" taken from throughout the sampling area. Proper Sampling Techniques, 3. Collection Process Sources University of Delaware Soil Testing Program, General Information Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
FloridaUnited StatesFlorida only. Other states set their own rules.	Soil or tissue tests to plan fertilizer on enrolled vegetable and agronomic crop landFDACS agricultural Best Management Practices, Florida Vegetable and Agronomic Crop (VAC) Operations	Result valid Manual Guidance text under BMP 1.2.1, not the checklist BMP: a soil test less than one year old, showing a need for phosphorus, before phosphorus is applied (crops other than multi-year crops). The manual says its narrative creates no obligation beyond the checklist BMPs, and the checklist BMP sets no age for the test.	Not specified	Not specified	Not specified	Not specified	ConditionalFDACS VAC BMP Manual, 2024 Edition (PDF), incorporated in Rule 5M-8.002, F.A.C.
Who it applies to, the exact wording and every source Who it applies to Vegetable and agronomic crop producers enrolled in the FDACS BMP Program. BMP 1.2.1 has them perform soil tests, tissue tests, or both to plan and manage fertilizer applications. Enrollment, or water quality monitoring instead, is required by Florida law inside basin management action plan (BMAP) areas. Outside the rule In the same Guidance text, multi-year crops may use a calibration curve from the soil test taken before planting for later phosphorus applications. Laboratory and analysis An extraction method listed in Appendix 2 for the soil type: Mehlich-3, AB-DTPA, water, Bray 1 or 2, ammonium acetate or Mehlich-1. Other methods need FDACS approval and a documented justification. In force from Under review Legal text FDACS Florida Vegetable and Agronomic Crop Operations BMP Manual, 2024 Edition (FDACS-P-01268, rev. 12/24), incorporated in Rule 5M-8.002, F.A.C., BMPs 1.2.1 and 1.2.2 (Right Rate), the Guidance text under BMP 1.2.1, and Appendix 2 The wording in the source Timing For crops other than multi-year crops, a soil test that is less than one year old is required and must demonstrate a need for P prior to any application of P. BMP 1.2.1, Guidance The contents of the narrative shall not be interpreted or construed as creating additional obligations or requirements that exceed the BMPs detailed in the BMP Checklist. Part B, Best Management Practices for VAC Operations, opening paragraph Perform soil tests, tissue tests, or both to appropriately plan and manage fertilizer applications. BMP Checklist, 1.2 Right Rate, item 1 Who it applies to Florida law requires agricultural producers and landowners located within BMAP areas to either enroll in the FDACS BMP Program and properly implement BMPs applicable to their property and operation or to conduct water quality monitoring activities as required by Rule Chapter 62-307, F.A.C. Introduction Perform soil tests, tissue tests, or both to appropriately plan and manage fertilizer applications. BMP 1.2.1 Outside the rule Multi-year crops can utilize a calibration curve for subsequent application of P based on the soil test taken before planting. BMP 1.2.1, Guidance Laboratory and analysis Use a soil extraction method listed in Appendix 2 appropriate for the soil type to perform soil test in 1.2.1. The use of other soil extraction methods must be approved by FDACS. Maintain documentation to justify using that method. BMP 1.2.2 Mehlich-3 extraction – Used on mineral or organic soils over most pH levels. Appendix 2, Soil Testing In force Publication No. FDACS-P-01268, rev. 12/24, Incorporated in Rule 5M-8.002, F.A.C. Title page Sources FDACS VAC BMP Manual, 2024 Edition (PDF), incorporated in Rule 5M-8.002, F.A.C. Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
FloridaUnited StatesFlorida only. Other states set their own rules.	Routine soil fertility samplingUF/IFAS Extension Soil Testing Laboratory, sampling advice	Repeat Soil pH at least once a year, if not every growing season	Up to 40 acres of a field section in commercial agriculture, uniform in management and topography	One composite per area uniform in management and topography. Separate samples for areas that differ.	Top 6 inches for most agronomic uses	8 to 15 locations per composite sample	Official guidanceUF/IFAS Extension SL547/SS763
Who it applies to, the exact wording and every source Who it applies to Advice for Florida growers and landscapes from UF/IFAS Extension (University of Florida). Not law. Laboratory and analysis Mehlich-3 extraction for mineral soils up to pH 7.4; AB-DTPA for alkaline soils outside Miami-Dade County. In force from Under review Legal text UF/IFAS Extension SL547/SS763, How to Read Reports from the UF/IFAS Extension Soil Testing Laboratory The wording in the source Timing It is recommended that soil be tested for pH at least once a year, if not every growing season, to ensure that the soil pH remains within the range for the crop/plant/grass species being grown. Section 2, Soil and Buffer pH Area per sample One sample represents an area that is uniform in management and topography, typically up to 40 acres of a field section in commercial agriculture. Soil Sampling Method For areas with different features and characteristics, separate samples should be collected and then submitted to the lab with appropriate identification. Soil Sampling Depth Soil sampling depth should be the top 6 inches for most agronomic and residential applications or 3 to 4 inches for maintenance of frequently mowed lawn or turf. Soil Sampling Cores Soils vary from spot to spot, so each sampled area is best represented by a composite sample collected from 8 to 15 locations. Soil Sampling Laboratory and analysis All mineral (e.g., sandy) soils with water pH up to 7.4 and all samples from Miami-Dade County with a soil pH of up to 8.2 are extracted using the Mehlich-3 extraction procedure. Section 3, Extractable Nutrient Test Values Alkaline soils (soil pH >7.4) from all other counties are currently being extracted by a procedure called Ammonium-bicarbonate-DTPA (AB-DTPA method) Section 3 Sources UF/IFAS Extension SL547/SS763 Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
GeorgiaUnited StatesGeorgia only. Other states set their own rules.	Routine soil fertility samplingUniversity of Georgia Cooperative Extension, Soil Test Handbook for Georgia	Repeat Every 2 to 3 years in most situations. Every year for high-value cash crops, fields testing high in P and K with none applied, or over 150 lb N per acre a year. Season One to six months before planting, at the same time each year	Most fields 5 to not more than 15 acres per sample. Smaller areas where soil, slope, drainage or management differ.	Cores at random over the area. Precision methods sample field subsections by soil type, topography, or crop growth or yield maps.	Plowed fields to plow depth (recommendations based on 6 inches for fertilizer, 8 inches for lime). Pastures and no-till 4 inches.	A minimum of 10 to 20 cores per composite. Earlier sampling studies found 20 cores needed for a 20-acre field, 15 for 10 acres and 10 for 5 acres.	Official guidanceUGA Cooperative Extension, Soil Test Handbook for Georgia (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Georgia fields, pastures and orchards from University of Georgia Cooperative Extension. Not law. In force from Under review Legal text UGA Cooperative Extension Special Bulletin 62, Soil Test Handbook for Georgia The wording in the source Timing For most situations soils need to be tested every 2 to 3 years. When to Sample Annual sampling is recommended (1) on areas where high-value cash crops such as tobacco and vegetables are grown, (2) on areas testing high in P and K where no phosphate or potash is recommended and none is applied, and (3) on areas where the annual nitrogen application rate exceeds 150 pounds of N per acre. When to Sample The best time to sample is one to six months prior to planting. When to Sample It’s important, therefore, that samples be taken at the same time each year so results from year to year can be compared. When to Sample Area per sample For most field conditions the size may range from 5 to not more than 15 acres. Variations in soil types, slope, drainage, or past management may require that smaller areas be sampled, resulting in three or more composite samples per field. Size of Area to Sample, Traditional Methods Method The division of field areas that can be sampled separately is typically based on soil type, field topography, or crop growth or yield maps from the previous season. Size of Area to Sample, Precision Agriculture Methods The cores should be taken at random over a section of the field or plot, and should be representative of the entire area. Number of Cores Depth Samples should be taken to the plow depth. The lime recommendations found in Tables A, B, C, and D are based on an 8-inch depth. Specific Sampling Procedures, Plowed Field Soils Fertilizer recommendations are based on a 6-inch depth Plowed Field Soils Pastures and no-till fields should be sampled to a depth of 4 inches. Pasture and No-Till Fields Cores It is recommended that a minimum of 10 to 20 cores be taken for a composite sample. Number of Cores For example, 20 cores were required for a 20-acre field, 15 cores for a 10-acre field, and 10 cores for a 5-acre field. Number of Cores Sources UGA Cooperative Extension, Soil Test Handbook for Georgia (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
HawaiiUnited StatesHawaii only. Other states set their own rules.	Routine soil fertility samplingUniversity of Hawaii CTAHR, guide to soil testing	Repeat At least once every 2 years Season Two to three months before planting	Larger areas such as pastures or orchards: uniform soil-test areas of 1 to 5 acres each	Map the area into uniform test areas; separate samples for different slope, soil color, drainage, texture or cropping history. Cores taken at random, for example in a zigzag.	4 inches for no-till fields and established pasture. 8 inches for conventionally tilled fields. Tree crops 0 to 8 inches plus a subsoil sample from 8 to 24 inches.	10 to 15 subsamples per composite sample	Official guidanceUH CTAHR, A Guide To Soil Testing For Hawaii’s Residents
Who it applies to, the exact wording and every source Who it applies to Advice for Hawaii farms, pastures, orchards and gardens from the University of Hawaii College of Tropical Agriculture and Human Resources. Not law. In force from Under review Legal text University of Hawaii at Manoa CTAHR, A Guide To Soil Testing For Hawaii’s Residents (Hue, Uchida and Ho) The wording in the source Timing Soil in fields or gardens should be tested at least once every two years. How to take a representative soil sample Plan to collect soil samples two to three months before planting How to take a representative soil sample Area per sample For larger areas like pastures or tree orchards, first make a detailed map of your area, then divide your map into smaller uniform soil-test areas of a few (1-5) acres each. How to take a representative soil sample Method Fields with different slope, soil color, drainage, apparent texture (for example, heavy, light, or A’a) or cropping history should be sampled separately. How to take a representative soil sample Each sample to be tested should be a thorough mix of the cores taken randomly, say, in a zigzag pattern as shown in Figure 1. How to take a representative soil sample Depth Soil subsamples consist of 1-inch thick slices of the soil taken to a specified depth, normally 4 inches for no-till fields or established pasture, lawn and turf and 8 inches for conventionally tilled fields. How to take a representative soil sample For tree crops (forests, nuts, tree fruits), where possible, collect a surface sample to a depth of 8 inches and a sub-soil sample from 8-24 inches deep. How to take a representative soil sample Cores A soil-test sample for each area should be a composite of 10-15 subsamples. How to take a representative soil sample Sources UH CTAHR, A Guide To Soil Testing For Hawaii’s Residents Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IdahoUnited StatesIdaho only. Other states set their own rules.	Annual soil samples on fields that receive livestock wasteIdaho State Department of Agriculture, Environmental and Nutrient Management rules	Repeat Every year, on all fields that received livestock waste, manure or process wastewater from the operation	Not specified	Representative samples taken by a Certified Soil Sampler using the methods of University of Idaho Soil Sampling Bulletin 704 (revised August 1997), incorporated by reference.	Not specified	Not specified	ConditionalIDAPA 02.04.30 (PDF, Idaho Office of the Administrative Rules Coordinator)
Who it applies to, the exact wording and every source Who it applies to Facilities required to keep a nutrient management plan: licensed dairies, beef cattle feeding operations and poultry operations required to have an NMP, and commercial truck wash operations, on every field where their livestock waste, manure or process wastewater was land applied. Laboratory and analysis An approved laboratory: one with valid certification from the North American Proficiency Testing Program under the Soil Science Society of America. Field identifiers Where an alternate depth is used for resource concerns, the sampler marks the depth on every sample and lab submission form. In force from Under review Legal text IDAPA 02.04.30, Rules Governing Environmental and Nutrient Management (Idaho Department of Agriculture), Sections 150, 151, 152, 104 and 110 The wording in the source Timing Facilities required to maintain an NMP, pursuant to these rules, must have soil samples collected each year from all fields owned or operated by the dairy, beef, poultry, or commercial truck wash operation to which livestock waste, manure, or process wastewater from the operation was land applied. Section 150, Soil Samples Method All soil samples collected pursuant to this chapter must be representative samples that are collected by a CSS at the depth indicated by the approved NMP for each facility. Samples shall be collected pursuant to SSB approved methods and submitted to an approved laboratory. Section 151, Soil Sample Collection August 1997 University of Idaho, Soil Sampling Bulletin 704 (revised). Section 104.01, Incorporation by Reference All persons who collect soil samples pursuant to Subchapter A must be a certified soil sampler via the Department Certification Program. Section 152, Soil Sample Certification Who it applies to Facilities required to maintain an NMP, pursuant to these rules, must have soil samples collected each year from all fields owned or operated by the dairy, beef, poultry, or commercial truck wash operation to which livestock waste, manure, or process wastewater from the operation was land applied. Section 150 All dairy farms licensed to sell milk for human consumption, beef cattle feeding operations required to implement a Nutrient Management Plan (NMP), poultry operations required to implement an NMP, certified NMP planners and certified soil samplers. Rule summary, Who does this rule apply to? Laboratory and analysis Approved Laboratory. A soil testing laboratory with a valid certification from the North American Proficiency Testing Program under the auspices of the Soil Science Society of America. Section 110.01, Definitions Field identifiers If resource concerns require an alternate sampling depth be used, the CSS must indicate the alternate depths on all samples and lab submission forms. Section 151 Sources IDAPA 02.04.30 (PDF, Idaho Office of the Administrative Rules Coordinator) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IdahoUnited StatesIdaho only. Other states set their own rules.	Soil testing to guide fertilizer managementUniversity of Idaho Extension, soil testing advice	Repeat Every year for best results; at least once each crop rotation cycle	Not specified	Divide each field into sampling units; take cores at random, meandering or zigzagging through each unit.	Fit to crop rooting depth; most fertilizer guides are based on 2 ft. Beans and sugar beets 2 ft. Potatoes 1 ft. Wheat fields would benefit from sampling to 5 ft in 1 ft increments.	By field size: under 5 acres 15; 5 to 10 acres 18; 10 to 25 acres 20; 25 to 50 acres 25; over 50 acres 30. Never fewer than 10.	Official guidanceUniversity of Idaho Extension BUL 915 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Idaho fields from University of Idaho Extension. Not law. In force from Under review Legal text University of Idaho Extension BUL 915, Soil Testing to Guide Fertilizer Management (October 2023) The wording in the source Timing For optimal soil fertility management, samples should be collected each year, and fields fertilized for a realistic potential yield of the intended crop. Sampling Frequency It is recommended to collect soil samples at least once during each crop rotation cycle (Walworth 2011). Sampling Frequency Method Soil cores must be taken randomly within each sampling unit; be sure to distribute sampling sites throughout the unit. Meander or zigzag throughout each sampling unit while collecting soil samples. Sampling Technique, 2. Plan out sampling path Since most fields are not completely uniform and may vary in topography, divide each field into sampling units (Figure 1). Sampling Technique, Divide field into units Depth With wheat rooting depth reaching up to 5 ft, it would be beneficial to sample wheat fields to 5 ft, in 1 ft increments. Sampling Technique, 4. Define sampling depth Although most fertilizer guides are based on a 2 ft depth, the sampling depth should be tailored to crop-specific rooting depth for the most accurate recommendations. For beans and sugar beets, the soil samples are typically collected from 2 ft. For potatoes, 1 ft samples are appropriate, due to a shallower rooting depth. Sampling Technique, 4. Define sampling depth Cores Table 1, field size in acres and recommended number of samples: <5 15; 5–10 18; 10–25 20; 25–50 25; >50 30 Table 1 (table, transcribed) *An absolute minimum of 10 samples from each sampling unit is necessary to obtain an acceptable sample. Table 1 footnote Sources University of Idaho Extension BUL 915 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IllinoisUnited StatesIllinois only. Other states set their own rules.	Soil sampling for pH, phosphorus and potassiumUniversity of Illinois Extension, soil sampling advice (from the Illinois Agronomy Handbook, Chapter 8)	Repeat Every 2 to 4 years when soils are at optimum fertility Season After harvest in the fall is ideal; same time of year each time Wait Avoid sampling within a few months after lime or fertilizer	Uniform applications: one composite per 2.5 acres. Site-specific: one per 1.1 acres. Zones seldom over 10 acres.	Grid points, five cores within a 10-foot radius of each point; or zones from yield maps, canopy data, soil type and history. Sample the same points each time, located by GPS or measuring wheel.	7 inches, the depth the Illinois recommendations are calibrated to	10 to 15 cores per composite, 15 to 20 for better representation. Grid points: five cores within a 10-foot radius.	Official guidanceUniversity of Illinois Extension, Soil Sampling
Who it applies to, the exact wording and every source Who it applies to Advice for Illinois commercial crop fields from University of Illinois Extension. Not law. In force from Under review Legal text University of Illinois Extension, Soil Sampling (Illinois Agronomy Handbook, Chapter 8: Managing Soil pH and Crop Nutrients) The wording in the source Timing Soil testing is strongly suggested every 2-4 years if soils are at an optimum level of fertility, based on producers’ goals, and base applications have been calculated. How and When to Sample Sampling should be avoided within a few months after a lime or fertilizer treatment due to a higher values. How and When to Sample After harvest in the fall is an ideal season to sample because soil moisture conditions are generally more stable How and When to Sample Area per sample This approach suggests sampling at the rate of one composite from each 2.5-acre area. Typical Soil Sampling Methods, Whole field uniform fertilizer applications This approach suggests collecting one sample from each 1.1-acre area that will provide a better representation of the actual field variability. Site-specific applications The size of zones can vary depending on field characteristics but seldom exceeds 10 acres. Zone sampling Method Each sample should consist of five soil cores, 1 inch in diameter, collected to a 7-inch depth from within a 10-foot radius around each point. Figure 2A caption it is important to collect samples from precisely the same points each time a field is tested. Sample locations can be identified using a global positioning system (GPS) unit or by accurately measuring the sample points with a device such as a measuring wheel. Typical Soil Sampling Methods Depth The fertilizer recommendation system in Illinois is based on crop response to fertility levels in the top 7 inches of the soil, which is the proper sampling depth for pH, phosphorus, and potassium. How and When to Sample Cores Soil samples should be a composite of 10 to 15 cores (whether grid or zone sampling) from the intended management area within a field, depending on field characteristics such as soil types, land or fertilizer uses, and terrain. Collecting 15-20 cores per area can improve representation. How and When to Sample Sources University of Illinois Extension, Soil Sampling Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IndianaUnited StatesIndiana only. Other states set their own rules.	Soil phosphorus test for manure application ratesIDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan	Result valid IDEM: the soil test used for a field’s manure rate must be no more than 4 years old on the date manure is applied there. A different frequency may be approved in the manure management plan.	IDEM: each soil test may represent no more than 20 acres (8.0937 ha)	IDEM: composite samples, or averaged results, within areas of up to 20 acres, with the procedure set out in the manure management plan. Grid sampling is good practice, not required.	Not specified	IDEM: 12 to 15 plugs recommended for a composite from a 20 acre area	Official guidanceIDEM, Guidance Manual for Indiana’s Confined Feeding Program (PDF)
Who it applies to, the exact wording and every source Who it applies to IDEM guidance for confined feeding operations (at least 300 cattle, 600 swine or sheep, 30,000 poultry or 500 horses in confinement) on the soil tests behind each field’s manure application rate. It explains the CFO rule, 327 IAC 19; it is not the rule text. Laboratory and analysis IDEM: phosphorus is the only element the CFO rules require. Bray P1 or Mehlich 3 test, reported in ppm. In force from Under review Legal text IDEM, Guidance Manual for Indiana’s Confined Feeding Program (December 29, 2014; references updated October 2019 and July 2023), Manure Management Plan section, pp. 25 to 28 (explaining 327 IAC 19-7-5(c) and 327 IAC 19-14-3) The wording in the source Timing The soil test you use to calculate a manure application rate for a particular field must be no more than 4 years old on the date that you apply manure to that field. IDEM CFO guidance manual, How often do I have to sample soil and manure? (See 327 IAC 19-7-5(c)), p. 25 A different frequency may be approved in your manure management plan. IDEM CFO guidance manual, How often do I have to sample soil and manure?, p. 25 Area per sample The CFO rules specify that a soil test must be obtained that provides sufficient information about soil fertility to allow for nutrient recommendations for existing or planned crops and soil tests may not represent more than 20 acres per sample. IDEM CFO guidance manual, Soil Testing Topics, Can I composite soil samples… (See 327 IAC 19-7-5(c)), p. 26 Method Yes, you can use composite sampling techniques and average test results within areas of up to 20 acres. IDEM CFO guidance manual, Soil Testing Topics, p. 26 The CFO rules require your soil testing procedures to be specified in your manure management plan. IDEM CFO guidance manual, Soil Testing Topics, p. 26 Although not required, using a grid to determine the locations where you will take samples is a good practice IDEM CFO guidance manual, Can I use grid sampling techniques…?, p. 27 Cores For example, you can take multiple plugs or grab samples across a 20 acre area (12-15 samples is recommended), mix the samples in a container, and take one composite sample from the container to send to the lab. IDEM CFO guidance manual, Soil Testing Topics, p. 26 Who it applies to In Indiana, an animal feeding operation with at least 300 cattle, 600 swine or sheep, 30,000 poultry, or 500 horses in confinement is a confined feeding operation (CFO). IDEM CFO guidance manual, Who is subject to the Confined Feeding Regulations? (See IC 13-18-10-1) You need soil and manure nutrient information to determine the nitrogen and phosphorus application rates for every land application event IDEM CFO guidance manual, Other Topics (See 327 IAC 19-14-3(c)), p. 28 Laboratory and analysis phosphorus is the only element required in a soil test to comply with the CFO rules. IDEM CFO guidance manual, What specific elements must soil be tested for? (See 327 IAC 19-7-5(c) and 327 IAC 19-14-3), p. 26 The soil phosphorus Bray P1/Mehlich 3 test must be used and soil phosphorus levels reported in parts per million (ppm). IDEM CFO guidance manual, What specific elements must soil be tested for?, p. 26 Sources IDEM, Guidance Manual for Indiana’s Confined Feeding Program (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IndianaUnited StatesIndiana only. Other states set their own rules.	Routine soil fertility samplingPurdue Extension soil sampling guidelines	Repeat Once every four years in most soils. Every two years on sandy or highly managed soils (irrigated, silage or hay fields). Season When no crop is standing: spring before planting or fall after harvest, before fertilizer or lime. Keep the same season each time.	Whole field: at least one composite per 20 acres. Grid cells 1 to 5 acres, 2.5 acres or less works best. Zones usually 2 to 10 acres.	Zig-zag pattern for whole-field sampling. Grid or zone sampling for variable-rate maps; zone sampling preferred over grid.	Conventional tillage: 0 to 8 inches. Conservation tillage: separate 0 to 4 inch sample for pH and lime, 0 to 8 inches for fertility.	10 to 20 subsamples per composite. Zones: two per acre, at least five. Grids: at least five for a 1 acre cell, 8 to 10 for 2.5 to 5 acre cells.	Official guidancePurdue Extension AY-368-W, Soil Sampling Guidelines (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Indiana fields from Purdue University Cooperative Extension Service. Not law. Laboratory and analysis Often best to use the same laboratory every year, so year-to-year changes reflect the soil rather than differences between laboratories. Field identifiers Label each bag with field and sample number. For zone sampling, record each sample or zone location. In force from Under review Legal text Purdue Extension AY-368-W, Soil Sampling Guidelines (November 2018) The wording in the source Timing In most soils, try to sample fields once every four years. AY-368-W, Sample timing, p. 6 In these circumstances, soil fertility can change rapidly and these fields should be sampled once every two years. AY-368-W, Sample timing (sandy or highly managed soils), p. 6 The most convenient time to collect soil samples is when there is no standing crop in the field (i.e. in the spring prior to planting or in the fall after harvest). AY-368-W, Sample timing, p. 6 Schedule soil sampling and testing prior to application of fertilizers or lime AY-368-W, Sample timing, p. 6 Keep sample collection timing consistent to avoid year-to-year variability. AY-368-W, Sample timing, p. 6 Area per sample Collect at least one composite per 20 acres. AY-368-W, Soil sampling for whole-field management, p. 4 Typical grid sizes range from 1 to 5 acres, with smaller grids (i.e., 2.5 acres or less) providing the best results. AY-368-W, Grid sampling, p. 5 In most cases, zones are between 2 and 10 acres in size. AY-368-W, Zone-based sampling, p. 5 Method collect composite samples in a zig-zag pattern (Fig. 3). AY-368-W, Soil sampling for whole-field management, p. 4 While grid sampling is preferred to whole-field sampling, it is inferior to the more informative zone-based sampling. AY-368-W, Grid sampling, p. 6 Depth 0-8 inches for pH/liming recommendations AY-368-W, Table 1, conventional tillage 0-4 inches for pH/liming AY-368-W, Table 1, conservation tillage (take separate samples) 0-8 inches for fertility analysis AY-368-W, Table 1, conservation tillage Cores Typically, a composite sample should be comprised of between 10 and 20 subsamples. AY-368-W, Sample collection, step 6, p. 2 As a rule of thumb, collect two subsamples per acre in a zone. Regardless of zone size, a minimum of five subsamples per zone should be collected. AY-368-W, Zone-based sampling, p. 5 For a one-acre grid cell, collect at least five subsamples. For grid cells between 2.5 and 5 acres, collect between 8 and 10 subsamples. AY-368-W, Grid sampling, p. 5 Laboratory and analysis For this reason, it is often desirable to use the same soil-testing laboratory every year. AY-368-W, Soil testing laboratories, p. 3 This will ensure that any observed change in soil-test results from year to year are attributable to true changes in soil fertility status and not due to deviations in testing practices between different laboratories. AY-368-W, Soil testing laboratories, p. 3 Field identifiers Names should contain identifiers to the field and sample number. AY-368-W, Sample collection, step 8, p. 3 it is especially important that samples be labeled with the correct zone and that the location of each sample or zone is recorded. AY-368-W, Zone-based sampling, p. 5 Sources Purdue Extension AY-368-W, Soil Sampling Guidelines (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IowaUnited StatesIowa only. Other states set their own rules.	Soil phosphorus and pH tests for the phosphorus indexIowa DNR manure management plans (MMP) for confinement feeding operations	Result valid Soil samples must be four years old or less Repeat A complete plan with new soil sampling for each field at least once every four years	No more than 10 acres per sample. One sample for a field of 15 acres or less. Up to 20 acres for the next sampling where manure went on at phosphorus-based rates.	Grid, management zone or soil type sampling, among others. Procedural details may be taken from ISU Extension CROP 31-8 (published as CROP 3108), NCR-13 Report 348 or other credible soil sampling publications.	0 to 6 inches	At least 10 cores per composite sample	ConditionalIowa Administrative Code 567, Chapter 65 (PDF, IAC 8/6/25)
Who it applies to, the exact wording and every source Who it applies to Anyone who must submit a manure management plan for a confinement feeding operation: construction permit applicants, owners of operations built or expanded after May 31, 1985 or building a manure storage structure, and people applying manure in Iowa from out-of-state confinement operations. Covers each field in the plan, the fields where the phosphorus index must be used. Outside the rule Small animal feeding operations (SAFO, 500 or fewer animal units), operations of 500 or fewer animal units that elect SAFO status for updated plans, construction permit applicants for an egg washwater storage structure, and research colleges for their research activities. Laboratory and analysis Phosphorus and pH. A laboratory enrolled in the IDALS soil testing certification program. Bray-1 phosphorus not accepted where soil pH is 7.4 or higher. In force from Under review Legal text Iowa Administrative Code 567, Chapter 65 (Animal Feeding Operations), Rule 567-65.111(11) and 65.111(12) The wording in the source Timing Soil samples shall be obtained from each field in the MMP, and the soil samples shall be four years old or less. 567 IAC 65.111(11) An operation must submit a complete MMP using a new phosphorus index, including soil sampling as required in subrule 65.111(11), for each field in the MMP a minimum of once every four years. 567 IAC 65.111(12)"h"(3) Area per sample Each soil sample shall represent no more than ten acres. For fields less than or equal to 15 acres, only one soil sample is necessary. 567 IAC 65.111(11)"c" If manure is applied as phosphorus-based rates within soil sampling periods, each soil sample may represent up to 20 acres for the next required soil sampling. 567 IAC 65.111(11)"f" Method Acceptable soil sampling strategies include but are not limited to grid sampling, management zone sampling, and soil type sampling. 567 IAC 65.111(11)"a" Procedural details can be taken from Iowa State University Extension and Outreach publication CROP 31-8, “Take a Good Soil Sample to Help Make Good Fertilization Decisions,” NCR-13 Report 348, “Soil Sampling for Variable-Rate Fertilizer and Lime Application,” effective January 1, 2001, or other credible soil sampling publications. 567 IAC 65.111(11)"a" Depth with each core containing soil from the top six inches of the soil profile. 567 IAC 65.111(11)"b" Cores Each soil sample must be a composite of at least ten soil cores from the sampling area, with each core containing soil from the top six inches of the soil profile. 567 IAC 65.111(11)"b" Who it applies to Soil sampling requirements for fields where the phosphorus index must be used. Soil samples shall be obtained from each field in the MMP 567 IAC 65.111(11), heading An applicant for a construction permit for a confinement feeding operation. 567 IAC 65.110(1)"a" The owner of a confinement feeding operation, other than a SAFO, if one of the following applies: 567 IAC 65.110(1)"b" The owner constructs a manure storage structure, regardless of whether the person is required to be issued a permit for the construction 567 IAC 65.110(1)"b"(2) A person who applies manure in Iowa that was produced in a confinement feeding operation, other than a small operation, located outside of Iowa. 567 IAC 65.110(1)"c" The confinement feeding operation was constructed or expanded after May 31, 1985, regardless of whether the confinement feeding operation structure was required to have a construction permit. 567 IAC 65.110(1)"b"(1) A person who submits an MMP shall include a phosphorus index as part of the MMP as required in subrule 65.111(12). 567 IAC 65.111(1)"c" Outside the rule “Small AFO” or “SAFO” means an AFO that has an animal unit capacity of 500 or fewer animal units. 567 IAC 65.1, definitions However, an MMP shall not be required of an applicant for an egg washwater storage structure or for a SAFO. 567 IAC 65.110(1)"a" An AFO otherwise required to submit an updated MMP and pay an annual compliance fee may make an election to be considered a SAFO for purposes of filing updated MMPs and annual compliance fees if the confinement feeding operation maintains an animal unit capacity of 500 or fewer animal units. 567 IAC 65.110(1)"e"(2) A research college is exempt from this subrule and the MMP requirements of rule … for research activities and experiments performed under the authority of the research college and related to confinement feeding operations. 567 IAC 65.110(1)"e"(1) Laboratory and analysis Each soil sample shall be analyzed for phosphorus and pH. 567 IAC 65.111(11) Soil analysis must be performed by a lab enrolled in the Iowa department of agriculture and land stewardship (IDALS) soil testing certification program. 567 IAC 65.111(11)"d" If soil pH is greater than or equal to 7.4, soil phosphorus data from the Bray-1 extraction method is not acceptable for use with the phosphorus index. 567 IAC 65.111(11)"e" Sources Iowa Administrative Code 567, Chapter 65 (PDF, IAC 8/6/25) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
IowaUnited StatesIowa only. Other states set their own rules.	Routine soil fertility samplingIowa State University Extension and Outreach soil sampling advice	Repeat Every 2 to 4 years for most crops, or once in a crop rotation, in the same crop each time Season Ideally after harvest and before fertilization. Not shortly after lime, fertilizer or manure. Avoid winter and frozen soil.	Grid: a suggested minimum of one sample per 2.5 acres. Beyond that, zone sampling is likely more effective. Otherwise one sample per uniform area.	Soil map unit or management zone sampling, or grid sampling. Cores in a random zigzag pattern across each area; grid points cover an area at least 50 feet across.	P, K, Zn and organic matter: 0 to 6 inches in all tillage systems. pH: 0 to 6 inches with tillage, top 2 to 3 inches in no-till and in hay or pasture.	At least 10 to 12 cores per sample. 15 to 20 for a better average. At least 20 with recent banded fertilizer or manure.	Official guidanceISU Extension and Outreach CROP 3108 (PDF, copy hosted by Iowa DNR)
Who it applies to, the exact wording and every source Who it applies to Advice for Iowa fields from Iowa State University Extension and Outreach. Not law. Iowa manure management rules point to it for procedure. Laboratory and analysis Tell the laboratory when the pH sample came from 2 to 3 inches or the lime will not be incorporated. Field identifiers Each bag identifies the field and sample area with a unique number. In force from Under review Legal text ISU Extension and Outreach CROP 3108, Take a Good Soil Sample to Help Make Good Fertilization Decisions (December 2016) The wording in the source Timing Fields should be sampled every 2-4 years for most crops, or once in a crop rotation. CROP 3108, How often to sample and test, p. 4 Fields should be in the same crop each time sampled in order to reduce the temporal variability of test results. CROP 3108, How often to sample and test, p. 4 Ideally, the best time would be after harvest and before fertilization. Do not sample shortly after a lime, fertilizer, or manure application or when the soil is excessively dry or wet. CROP 3108, When to sample, p. 1 Sampling at other times such as in the winter, and especially with frozen soil, is discouraged CROP 3108, When to sample, p. 1 Area per sample No one grid size best fits all fields, but a suggested minimum size is one sample per 2.5 acres. If considering a larger grid sampling size, a zone sampling approach would likely be more effective. CROP 3108, Sampling using a grid pattern, p. 3 Each sample should represent a uniform field area with similar past management. CROP 3108, Sampling using soil maps and management zones, p. 1 Method For soil map unit and management zone sampling, or to represent the entire area of a grid cell, take separate cores in a random zigzag pattern from each sampling area. CROP 3108, Collecting a representative sample, p. 4 For grid-point sampling, take the cores in a random pattern from the area of the identified sample point, which should be at least 50 feet in diameter. CROP 3108, Collecting a representative sample, p. 4 Depth Use this sample depth in all tillage systems when sampling for P, K, Zn, and organic matter. CROP 3108, Sampling depth, p. 4 (the depth is 0 to 6 inches) from a depth of 0 to 6 inches because research has shown that is the best and most cost-effective depth for Iowa conditions. CROP 3108, Sampling depth, p. 4 Samples for pH and buffer pH should be collected from a depth of 6 inches when the field is managed with tillage, but from the top 2-3 inches in no-till fields and forages for hay or pasture CROP 3108, Sampling depth, p. 4 Cores As a minimum, take 10-12 cores or borings per sample and place all soil in a sample bag. CROP 3108, Collecting a representative sample, p. 4 For better representation of the average condition within an area, take 15 to 20 cores. Take at least 20 cores if the field has recent banded fertilizer or manure. CROP 3108, Collecting a representative sample, p. 4 Laboratory and analysis In these tillage and cropping conditions the laboratory must be informed that the sample was taken from a depth of 2-3 inches or that the lime will not be incorporated. CROP 3108, Sampling depth, p. 4 Field identifiers Check that each bag clearly identifies the field and sample area with a unique number. CROP 3108, Sending samples for testing, p. 4 Sources ISU Extension and Outreach CROP 3108 (PDF, copy hosted by Iowa DNR) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
KansasUnited StatesKansas only. Other states set their own rules.	Routine soil fertility samplingK-State Research and Extension, Soil Testing Laboratory sampling advice	Repeat Row crops: immobile nutrients every 2 to 4 years, at a consistent time in the rotation. Permanent sod: every 2 to 4 years. Mobile nutrients: before responsive crops. Season Row crops and sod: fall or spring. Nitrate, chloride and sulfur profile: late fall or early spring.	Not specified	Divide each field into uniform areas of the same soil texture, colour, slope, and fertilization and cropping history; sample each area.	Row crops 0 to 6 inches. Permanent sod 0 to 4 inches. Nitrogen, chloride or sulfur tests 0 to 24 inches.	10 to 15 cores or slices per area	Official guidanceK-State Research and Extension MF734, Soil Testing Laboratory (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Kansas fields from K-State Research and Extension. Not law. Field identifiers Label the container clearly and record the sample identification on the container and the information sheet. In force from Under review Legal text K-State Research and Extension MF734, Soil Testing Laboratory (June 2016) The wording in the source Timing every 2 to 4 years MF734, Sampling Frequency table, Row crops, immobile nutrients Consistent time in rotation MF734, Sampling Frequency table, Row crops before responsive crops MF734, Sampling Frequency table, Row crops, mobile nutrients Fall or spring MF734, Sampling Frequency table, Sampling Time for Row crops (immobile) and Permanent sod Soil samples for nitrate testing should be collected in the late fall or early spring before significant mineralization has occurred. MF734, When to Sample and What to Test Every 2 to 4 years MF734, Sampling Frequency table, Permanent sod Method Draw a map of the sample area on the information sheet and divide your fields into uniform areas. Each area should have the same soil texture, color, slope, and fertilization and cropping history. MF734, Soil Sample Collection, step 2 Depth Row crops should be sampled at 6 inches deep and permanent sod at 4 inches. For available nitrogen, chloride, or sulfur tests, a 24-inch sample is necessary. MF734, Soil Sample Collection, step 3 Cores From each area, sample 10 to 15 cores or slices. MF734, Soil Sample Collection, step 3 Field identifiers Label the soil container clearly. Record the sample identification on the container and information sheet. MF734, Soil Sample Collection, step 5 Sources K-State Research and Extension MF734, Soil Testing Laboratory (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
KentuckyUnited StatesKentucky only. Other states set their own rules.	Routine soil fertility samplingUniversity of Kentucky Cooperative Extension soil sampling advice	Repeat Most fields every three to four years. Every year for high-value crops (tobacco, commercial horticulture, alfalfa, red clover, corn silage) and for manured fields. Season Fall (September to December) or spring (February to April), at the same time of year each time	No more than 20 acres per sample, except where soils, past management and cropping history are quite uniform. Grid cells: 2.5 acres is the industry standard.	Sample smaller areas by soil type, cropping history, erosion or past management; yield maps help. Grid sampling: treat each cell as a field.	Tilled areas: depth of tillage, usually 6 to 8 inches. Pastures, no-till and minimum-till: 3 to 4 inches.	At least 10 cores for small areas, up to 30 for larger fields. At least 10 across each grid cell.	Official guidanceUK Cooperative Extension AGR-16, Taking Soil Test Samples (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Kentucky fields from University of Kentucky Cooperative Extension. Not law. Field identifiers Keep records of where each sample was taken. In force from Under review Legal text University of Kentucky Cooperative Extension AGR-16, Taking Soil Test Samples (revised December 2003) The wording in the source Timing Most fields should be sampled every three to four years. AGR-16, Sample Timing, p. 1 High-value crops, such as tobacco, commercial horticultural crops, alfalfa, red clover, and corn silage, should be sampled annually so that plant nutrient levels can be monitored more closely. AGR-16, Sample Timing, p. 1 Application of manure can change soil test phosphorus, potassium, and zinc levels dramatically, so sampling manured fields each year is also recommended. AGR-16, Sample Timing, p. 1 Soil samples can be collected through much of the year, although fall (September to December) or spring (February to April) are the best times. AGR-16, Sample Timing, p. 1 In either case, a field should always be sampled the same time of the year in order to make historical comparisons. AGR-16, Sample Timing, p. 1 Area per sample An individual sample should represent no more than 20 acres except when soils, past management, and cropping history are quite uniform. AGR-16, Collecting Field Crop Samples, p. 1 Currently the industry standard grid size is 2.5 acres, but Kentucky research shows that variability within areas as small as one acre can be as great as the variability within the entire field. AGR-16, Grid Soil Sampling, p. 2 Method The most representative sample can be obtained from a large field by sampling smaller areas on the basis of soil type, cropping history, erosion, or past management practices (Figure 2). AGR-16, Collecting Field Crop Samples, p. 1 If a few years of yield maps are available, these can help identify areas of the field that should be sampled separately. AGR-16, Collecting Field Crop Samples, p. 1 Because soil variability is so high, it is important to treat each grid cell as a field. AGR-16, Grid Soil Sampling, p. 2 Depth Take soil cores to the depth of the tillage operation (usually 6 to 8 inches). AGR-16, Sample Depth, Tilled Areas, p. 3 Take soil cores to a depth of 3 to 4 inches for pastures, no-till planting (where fertilizer or lime remains on the soil surface), and minimum-till planting (where fertilizer is incorporated only in the surface 1 to 2 inches). AGR-16, Sample Depth, Non- or Reduced-Tilled Areas, p. 3 Cores Collect at least 10 soil cores for small areas and up to 30 cores for larger fields. AGR-16, Collecting Field Crop Samples, p. 1 At least 10 random samples should be collected across the entire grid cell, rather than a few cores from the center of the grid (Figure 3). AGR-16, Grid Soil Sampling, p. 2 Field identifiers Keep good records indicating where each sample was taken. AGR-16, Collecting Field Crop Samples, p. 1 Sources UK Cooperative Extension AGR-16, Taking Soil Test Samples (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
LouisianaUnited StatesLouisiana only. Other states set their own rules.	Routine soil fertility samplingLSU AgCenter soil sampling, testing and test interpretation advice	Repeat At least once every two to three years, or once per complete crop rotation Season At the same time each year	Zone sampling: one composite per 10 acres. Grid sampling: one composite per 2.5 acres; start new fields at 1 acre.	Zone or grid sampling, subsamples in a zigzag pattern within each zone or grid cell. In furrow-irrigated fields, sample the bed top 4 to 6 inches from the row.	0 to 6 inches	12 to 15 subsamples per composite: one to two per acre for zones, five to six per acre for grids. More where fertilizer was banded or manure spread.	Official guidanceLSU AgCenter P3934, Soil Sampling, Testing and Test Interpretation (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Louisiana fields from the LSU AgCenter. Not law. Laboratory and analysis A certified soil laboratory. Louisiana fertilizer recommendations are based on the Mehlich-3 extraction of 0 to 6 inch samples. Use the same laboratory each year. Field identifiers Label each bag with farm name and location, sampling date and depth, previous crop and the crop to be grown. In force from Under review Legal text LSU AgCenter P3934, Soil Sampling, Testing and Test Interpretation for Fertilizer Recommendations (July 2024) The wording in the source Timing Frequency of testing: Test soil at least once every two to three years or once per complete crop rotation. P3934, Soil Sampling Procedure, item 1, p. 2 Take soil samples at the same time each year, maintaining a consistent depth of 0 to 6 inches using a soil probe or auger (see Figure 1). P3934, Soil Sampling Procedure, item 2, p. 2 Area per sample Zone sampling: Take one composite sample for every 10 acres. P3934, Sampling density, p. 2 Grid sampling: Take one composite sample for every 2.5 acres. A smaller grid is better than a large grid. For new fields without prior soil testing information, it is advisable to start with a smaller grid (1 acre). P3934, Sampling density, p. 2 Method Collect subsamples in a zigzag pattern within each zone or grid. P3934, Soil Sampling Procedure, p. 2 In furrow irrigation systems, sample from the top of the bed, 4 to 6 inches away from the crop row. P3934, Preparation for sampling, p. 2 Depth Take soil samples at the same time each year, maintaining a consistent depth of 0 to 6 inches using a soil probe or auger (see Figure 1). P3934, Soil Sampling Procedure, item 2, p. 2 Cores Each composite sample should include 12 to 15 subsamples (one to two per acre for zone sampling and five to six per acre for grid sampling). P3934, Subsample collection, p. 2 More subsamples are required for fields with past fertilizer banding or manure spreading. P3934, Soil Sampling Procedure, p. 2 Laboratory and analysis Test soil samples in a certified soil lab, such as the LSU AgCenter Soil Testing and Plant Analysis Lab in Baton Rouge. P3934, Soil Testing, item 1, p. 3 In Louisiana, fertilizer recommendations are based on the Mehlich-3 soil extraction method for samples collected from a 0- to 6-inch depth. P3934, Soil Testing, item 1, p. 3 Analyze soil samples in the same lab each year to maintain a consistent historic record. P3934, Soil Testing, item 2, p. 3 Field identifiers Clearly label the bag with the farm name and location, sampling date and depth, previous crop and the expected crop to be grown. P3934, Sample handling, p. 2 Sources LSU AgCenter P3934, Soil Sampling, Testing and Test Interpretation (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MaineUnited StatesMaine only. Other states set their own rules.	Soil tests in a nutrient management planMaine Nutrient Management Act, nutrient management plans (NMP)	Repeat The statute sets no interval; it requires soil test results in the plan. Maine DACF guidance: soil and manure tests in the plan updated at least every 5 years, each field soil tested at least once every 5 years.	Not specified	Not specified	Not specified	Not specified	Conditional7 M.R.S. section 4204, Nutrient management plan (Maine Legislature)
Who it applies to, the exact wording and every source Who it applies to Farms that confine and feed 50 or more animal units at any one time, store or use more than 100 tons a year of manure not generated on the farm, are the subject of a verified complaint of improper manure handling, or store or use regulated residuals. Soil tests cover the land the plan designates for manure spreading or irrigation. In force from Under review Legal text Maine Revised Statutes Title 7, Chapter 747 (Nutrient Management Act), 7 M.R.S. section 4204, subsections 1-A(E) and 2 The wording in the source Timing Results of soil and manure tests and an analysis of any off-farm nutrients planned for growing crops. These tests must be updated at least every 5 years; Maine DACF Nutrient Management Plans brochure (guidance, not the statute), What are some components of an NMP? Each field should be soil tested at least once every 5 years to determine P, K, Mg, Ca and pH levels. Maine DACF Manure Utilization Guidelines (guidance, not the statute), item b, Soil test each field Who it applies to Results of soil tests for land designated in the plan for manure spreading or manure irrigation; 7 M.R.S. section 4204(1-A)(E) A farm that confines and feeds 50 or more animal units at any one time; 7 M.R.S. section 4204(2)(A) A farm that stores or utilizes more than 100 tons of manure per year not generated on that farm; 7 M.R.S. section 4204(2)(B) A farm that is the subject of a verified complaint of improper manure handling; or 7 M.R.S. section 4204(2)(C) A farm that stores or utilizes regulated residuals. 7 M.R.S. section 4204(2)(D) Sources 7 M.R.S. section 4204, Nutrient management plan (Maine Legislature) Law Maine DACF, Nutrient Management Plans brochure (February 2016) Guidance Maine DACF, Manure Utilization Guidelines (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MaineUnited StatesMaine only. Other states set their own rules.	Routine soil fertility samplingUniversity of Maine soil sampling instructions and Cooperative Extension advice	Repeat At least once every three years; more often for problem areas or heavy nutrient use Season Early spring after the frost is out, or fall before the ground freezes	Up to 8 acres per sample where past treatment and soil type are uniform. Separate samples for low spots, trouble spots, different soils and differently treated areas.	Uniform sampling areas; keep a permanent field sampling map.	Row crops or new seedings: plow depth, about 8 inches. Sod (hayfields, lawns): 3 to 4 inches. Tree crops: 12 inches.	About 15 spots per sample area	Official guidanceMaine Soil Testing Service, Field and Soil Sample Information form, sampling instructions (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Maine fields from the University of Maine. Not law. Field identifiers Label each container with the sample area and last name, matching the field sampling map and the form. In force from Under review Legal text Maine Soil Testing Service, sampling instructions (Field and Soil Sample Information form, 2018), and UMaine Extension Bulletin 2286 The wording in the source Timing Test your soil at least once every three years. Bulletin 2286, How often should I test the soil? You may want to test more often if you have a problem area or if you’ve applied lots of nutrients. Bulletin 2286 you should test soil well before the growing season, such as in early spring after the frost is out of the soil, or in the fall before the ground freezes. Bulletin 2286, What time of year should I test my soil? Area per sample In areas where past treatments and soil types are uniform, limit the sampling area to 8 acres in size. Form, Instructions, 3 Areas of Sampling Low spots, trouble spots, and areas with obvious differences in soil type should be treated as separate sampling areas. Also, areas that have been treated differently in the past should be sampled separately. Form, Instructions, 3 Areas of Sampling Method Make a permanent field sampling map for your reference when test results are returned. Form, Instructions, 3 Areas of Sampling Low spots, trouble spots, and areas with obvious differences in soil type should be treated as separate sampling areas. Form, Instructions, 3 Areas of Sampling Depth Areas in sod, such as lawns or hayfields, should be sampled to a 3-or 4-inch depth. Areas under tree crops should be sampled to a 12-inch depth. Form, Instructions, Depth Areas to be planted to row crops or seeded down should be sampled to plow depth (or about 8 inches.) Form, Instructions, Depth Cores Take soil from approximately l5 different spots in the sample area. Form, Instructions, Take Representative Sample (the PDF prints "l5" with a lower-case L) Field identifiers The container from each sample area should be identified on the side with the identification of the sample area and your last name. Form, Instructions, 7 Label the Containers Be sure identifying names agree with your map of sample areas, so when test results are returned there will be no question of where the samples were taken. Form, Instructions, 7 Label the Containers Sources Maine Soil Testing Service, Field and Soil Sample Information form, sampling instructions (PDF) Guidance UMaine Extension Bulletin 2286, Know Your Soil: Testing Your Soil Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MarylandUnited StatesMaryland only. Other states set their own rules.	Soil analysis results in a nutrient management planMaryland Nutrient Management Program (Maryland Department of Agriculture)	Result valid Soil analysis results valid for 3 years, unless a documented exception applies	Not specified	Standard soil sampling methods acceptable to the Department, per field or management unit. Documented variations: larger uniform fields or a crop rotation as one unit, combined strip-cropped fields, smaller units for specialized production.	Not specified	Not specified	ConditionalCOMAR 15.20.08.05, Required Plan Recommendations
Who it applies to, the exact wording and every source Who it applies to Agricultural operations with gross annual income of 2,500 dollars or more, or eight or more animal units, that use chemical fertilizer, animal manure or biosolids, for each field or management unit in the plan. Outside the rule The 3-year validity does not bind where documented: a new-technology management system needs less frequent analysis, no nutrient application is needed, or nutrients go on less than once every 3 years. Laboratory and analysis Standard soil analysis methods acceptable to the Maryland Department of Agriculture. In force from Under review Legal text COMAR 15.20.08, Nutrient Management Regulations, and COMAR 15.20.07, COMAR 15.20.08.05D; 15.20.07.05; 15.20.08.03B(2) The wording in the source Timing Soil analysis results for a plan are valid for 3 years, except if the following conditions exist and are documented by the consultant or certified farm operator: COMAR 15.20.08.05D(3) Method Soil analysis results for each field or management unit shall be based on standard soil sampling and analysis methods acceptable to the Department. COMAR 15.20.08.05D(1) Soil samples collected from larger fields or acreage with uniform characteristics, including soil types, moisture, or fertility management history; crop rotations may be sampled as one management unit; COMAR 15.20.08.05D(2)(a) Soil samples from fields, such as those common to strip cropping, which may be combined if the soils, previous cropping history, and soil fertility management are similar; and COMAR 15.20.08.05D(2)(b) Any specialized production unit which may warrant smaller sampling units. COMAR 15.20.08.05D(2)(c) Who it applies to Has a gross annual income of $2,500 or more, or has eight or more animal units. COMAR 15.20.08.03B(2)(b), definition of agricultural operation An operator who uses chemical fertilizer, animal manure, or biosolids, as provided in Regulation .04A of this chapter, shall have a nutrient management plan COMAR 15.20.07.05A Outside the rule A less frequent soil analysis is required to implement a management system based on new technologies; COMAR 15.20.08.05D(3)(a) The management system does not require any nutrient application; or COMAR 15.20.08.05D(3)(b) The management system requires nutrient application at a frequency less than once every 3 years. COMAR 15.20.08.05D(3)(c) Laboratory and analysis Soil analysis results for each field or management unit shall be based on standard soil sampling and analysis methods acceptable to the Department. COMAR 15.20.08.05D(1) Sources COMAR 15.20.08.05, Required Plan Recommendations Law COMAR 15.20.08.03, Definitions Law COMAR 15.20.07.05, Plan Implementation Requirements Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MarylandUnited StatesMaryland only. Other states set their own rules.	Routine soil fertility samplingUniversity of Maryland Extension soil sampling advice	Repeat At least once every three years, more often if possible Season Consider the same month each round. Fall after harvest and before nutrient applications is recommended. Wait At least six weeks after fertilizer or manure	Not specified	Sample each management unit separately, cores at random across the unit. Grid or zone sampling where it fits the farm.	Fertility, cropland and pasture: 0 to 8 inches. Pasture and continuous no-till: a second 0 to 2 inch sample for pH only.	At least 15 to 20 cores for units of about 20 acres or less. At least one per acre for 20 to 30 acres. Less than one per acre is acceptable above 40 acres.	Official guidanceUniversity of Maryland Extension FS-1184 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Maryland fields from University of Maryland Extension. Not law. Laboratory and analysis A regional soil testing laboratory suitable for nutrient management planning in Maryland (UM-ANMP list). In force from Under review Legal text University of Maryland Extension FS-1184, Soil Sampling for Optimizing Agricultural Production in Maryland (November 2021) The wording in the source Timing Soil samples should be collected at least once every three years, more often if possible. FS-1184, When to Sample, p. 1 For each new round of soil sampling, consider collecting samples in the same month of the year to reduce seasonal effects and associated variability. FS-1184, When to Sample, p. 1 sampling in the fall after harvest but before any nutrient applications is recommended. FS-1184, When to Sample, p. 1 Do not collect soil samples within a minimum of six weeks of fertilizer or manure applications to reduce the risk of more variable and non-representative results. FS-1184, When to Sample, p. 1 Method Sample a management unit by pulling individual soil cores randomly throughout the entire management unit and mixing those cores into one sample for analysis. FS-1184, How to Sample, p. 3 Grid- or zone-based precision soil sampling may be appropriate when considering intended farm management, equipment capabilities, and field features. FS-1184, Where to Sample, p. 1 Depth For soil fertility assessment of cropland and pasture fields and the Fall Soil Nitrate Test (FSNT), sample to a depth of 0 to 8 inches (see Figures 5 and 6). FS-1184, Soil Sampling Depth, p. 3 For pasture and continuous no-till cropland fields, a second sample to a depth of 0 to 2 inches is recommended to be taken and analyzed for pH only. FS-1184, Soil Sampling Depth, p. 3 Cores Collect a minimum of 15 to 20 soil cores from field management units that are ~20 acres or less. At least one soil core per acre is recommended for management units that are 20 to 30 acres. A sampling intensity of less than one soil core per acre is acceptable for management units exceeding 40 acres. FS-1184, How to Sample, p. 3 Laboratory and analysis A list of regional soil testing laboratories suitable for nutrient management planning in Maryland can be found at the University of Maryland Agricultural Nutrient Management Program’s (UM-ANMP) website. FS-1184, Sample Preparation, p. 4 Sources University of Maryland Extension FS-1184 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MinnesotaUnited StatesMinnesota only. Other states set their own rules.	Soil phosphorus tests on land receiving feedlot manureMinnesota feedlot rules (MPCA), land application of manure	Repeat At least once every four years	Not specified	Not specified	Upper six inches	Not specified	ConditionalMinnesota Rules, part 7020.2225 (Revisor of Statutes)
Who it applies to, the exact wording and every source Who it applies to Land receiving manure or process wastewater from animal feedlots, or manure storage areas, capable of holding 300 or more animal units. Laboratory and analysis Phosphorus by the Bray P1 or Olsen test. Fields over the set phosphorus levels need a manure management plan submitted with a permit application. In force from Under review Legal text Minnesota Rules, part 7020.2225, Land application of manure, Part 7020.2225, subpart 3, item C The wording in the source Timing soil samples from the upper six inches must be collected at a minimum frequency of once every four years and analyzed for phosphorus using the Bray P1 or Olsen test. Minn. R. 7020.2225, subp. 3, item C Depth soil samples from the upper six inches must be collected at a minimum frequency of once every four years Minn. R. 7020.2225, subp. 3, item C Who it applies to For land receiving manure or process wastewater from animal feedlots capable of holding 300 or more animal units or manure storage areas capable of holding the manure produced by 300 or more animal units, Minn. R. 7020.2225, subp. 3, item C Item C applies only to animal feedlots with a capacity of 300 or more animal units and manure storage areas capable of holding the manure produced by 300 or more animal units. Minn. R. 7020.2225, subp. 3, opening Laboratory and analysis analyzed for phosphorus using the Bray P1 or Olsen test. If soil phosphorus levels exceed the levels in subitems (1) and (2), then the owner must complete a manure management plan in accordance with subpart 4, item D, and submit it with a permit application to the agency or delegated county for review Minn. R. 7020.2225, subp. 3, item C Sources Minnesota Rules, part 7020.2225 (Revisor of Statutes) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MississippiUnited StatesMississippi only. Other states set their own rules.	Routine soil fertility samplingMississippi State University Extension soil testing advice	Repeat Each field once every 3 years or once per crop rotation Season Spring plantings: late October to January. Fall plantings: May to early August.	Not specified	Divide fields into uniform areas using a soil map; cores at random in a zigzag pattern; row crops between the rows.	Cropland: plow depth or another constant depth, generally 6 inches. Pastures and lawns: 4 to 6 inches.	At least 15 to 20 cores. 30 or more if the soil was limed or broadcast-fertilized in the last 2 years.	Official guidanceMSU Extension Publication 3858, Soil Testing for the Farmer (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Mississippi fields from Mississippi State University Extension. Not law. Field identifiers Label each sample (at most five characters) and keep a map of the areas sampled. In force from Under review Legal text Mississippi State University Extension Publication 3858, Soil Testing for the Farmer (POD-07-26) The wording in the source Timing Test each field once every 3 years or once per crop rotation. P3858, How Often and When to Test For fall plantings, take samples in May, June, July, and early August. For spring plantings, collect the samples the latter part of October, November, December, and January. P3858, How Often and When to Test Method Gather cores at random in a zigzag pattern over the area involved. P3858, Get a composite sample, 3b Sample a row-crop field between the rows, thus avoiding fertilizer band areas. P3858, How to Take Good Samples, 2d Using a soil map, sample the soils in a field; sample separately the light- and dark-colored soils and recently limed and unlimed areas (see map next page). P3858, How to Take Good Samples, 2a Divide fields into uniform areas. P3858, step 4 Depth Sample cropland to plow depth or another constant depth, depending on crop and tillage practices. Generally, a 6-inch depth is recommended. P3858, How to Take Good Samples, 2b Sample pastures and lawns to a 4- to 6-inch depth. P3858, How to Take Good Samples, 2c Cores To get a representative soil sample, gather at least 15 to 20 cores. If the tilled soil has been limed or fertilized by broadcasting in the last 2 years, take 30 or more individual cores, depending on soil variability or unknown locations of fertilizer bands. P3858, Get a composite sample, 3a Field identifiers Label carefully to ensure identification (maximum of five digits or characters). P3858, Process the soil sample, 5d Prepare a map or sketch of your farm or field layout, showing areas sampled. P3858, Process the soil sample, 5d Sources MSU Extension Publication 3858, Soil Testing for the Farmer (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MissouriUnited StatesMissouri only. Other states set their own rules.	Current soil test results for CAFO manure applicationMissouri DNR CAFO Nutrient Management Technical Standard	Result valid Re-sample before manure application when the soil test is more than five years old, or the phosphate surplus since the last test exceeds 500 lb/acre	Approximately 20 acres or less per sample. Grid alternative: cells under 3 acres.	Per MU Guides G9215 (pastures) and G9217 (row and hay crops). Georeferenced grid sampling is an alternative.	6 to 8 inches	At least 15 representative cores per sample, more on pastures or where phosphorus was banded. Grid: at least 10 cores within 15 feet of the grid point.	Official guidanceMissouri DNR CAFO Nutrient Management Technical Standard, March 4, 2009 (PDF, copy in the MU CAFO operator curriculum)
Who it applies to, the exact wording and every source Who it applies to Missouri DNR technical standard (March 4, 2009) for land application fields in the nutrient management plans of Class I CAFOs. Compliance is how a CAFO shows a precipitation-related discharge qualifies as agricultural stormwater. A department standard, not the regulation text. Laboratory and analysis A laboratory accredited by the Missouri Soil Testing Association, using University of Missouri Soil Testing Laboratory procedures. In force from Under review Legal text Missouri Concentrated Animal Feeding Operation Nutrient Management Technical Standard (Missouri DNR, March 4, 2009), Section III, A1(1) The wording in the source Timing Fields should be re-sampled before manure application when: NMTS, III A1(1)f The soil test is greater than five years old; or NMTS, III A1(1)f.i Phosphate surplus (actual applied phosphate minus actual removed phosphate) for the field has exceeded 500 lbs/acre since the last soil test; NMTS, III A1(1)f.ii Area per sample The average field area represented by a soil sample should be approximately 20 acres or less; NMTS, III A1(1)b Grid size should be less than three acres and at least 10 cores should be obtained from within 15 feet of the central grid point; NMTS, III A1(1)d Method MU Guides G9215 (for pastures) and G9217 (for row and hay crops); NMTS, III A1(1)a operations may elect to use a geo-referenced grid soil sampling method instead. NMTS, III A1(1)d Depth Soil sampling depth should be six to eight inches; NMTS, III A1(1)e Cores Each soil sample should be comprised of a well-mixed subsample derived from at least 15 representative cores from the sampled field area; more cores are recommended on pastures or where phosphorus has been band applied; NMTS, III A1(1)c Grid size should be less than three acres and at least 10 cores should be obtained from within 15 feet of the central grid point; NMTS, III A1(1)d Who it applies to The department’s CAFO regulations require the development and implementation of a field specific Nutrient Management Plan (NMP), meeting the criteria prescribed in 10 CSR 20-6.300(5)(A)-(I), at all Class I CAFOs. NMTS, I.A Authority and Purpose CAFOs will qualify for the Agriculture Stormwater Discharge exemption when they can demonstrate compliance with this NMTS at the time of a precipitation-related discharge from land application areas. NMTS, I.A Authority and Purpose Laboratory and analysis Soil samples should be analyzed at soil testing laboratories accredited by the Missouri Soil Testing Association NMTS, III A1(1)g using procedures recommended by the University of Missouri Soil Testing Laboratory. NMTS, III A1(1)g Sources Missouri DNR CAFO Nutrient Management Technical Standard, March 4, 2009 (PDF, copy in the MU CAFO operator curriculum) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MissouriUnited StatesMissouri only. Other states set their own rules.	Routine soil fertility sampling, hayfields and row cropsUniversity of Missouri Extension soil sampling advice	Repeat Every three to five years, at the same time of year as the last sample Season When the field is idle: fall and winter after harvest for forages and spring crops; summer for winter wheat and fall-seeded crops Wait At least three months after phosphorus fertilizer, lime or manure	Sampling areas typically no more than 20 acres. Grid sampling: typically one sample per 2.5 acres or less.	Divide fields into areas expected to be similar or managed alike; zigzag across the whole area. Grid sampling for variable rate, high-value fields or unknown history.	6 to 7 inches for most objectives. Long-term no-till: a separate 0 to 2 inch sample for surface pH.	10 to 20 cores. 15 to 20 with manure, banded fertilizer or other variation; 10 to 15 on uniform, broadcast-fertilized fields. 30 cores in a set pattern where injection bands are known.	Official guidanceMU Extension G9217, Soil Sampling Hayfields and Row Crops (PDF, CAFO operator curriculum copy)
Who it applies to, the exact wording and every source Who it applies to Advice for Missouri hayfields and row crops from University of Missouri Extension. Not law. Laboratory and analysis A laboratory accredited by the Missouri Soil Testing Association (MSTA). Field identifiers Label each sample with field and subfield names. In force from Under review Legal text MU Extension Guide G9217, Soil Sampling Hayfields and Row Crops The wording in the source Timing Sample your fields every three to five years. It is also recommended that you sample a field at the same time of year as your last sample because some soil test levels fluctuate during the year. G9217, When should I sample? It is best to wait at least three months after application of phosphorus fertilizer, lime or manure before taking a soil sample. G9217, When should I sample? The best time to collect soil samples is when the field is idle and enough time is available to plan fertilizer and lime applications for the next crop. G9217, When should I sample? Sampling after harvest in the fall and winter usually works best for forages and spring-seeded crops. G9217, When should I sample? For winter wheat and fall-seeded crops, sampling while the field is idle in the summer works well. G9217, When should I sample? Area per sample Typical sampling areas should not exceed 20 acres. G9217, How should I divide my fields? Grid soil sampling is a method of intensively sampling your field, typically obtaining a sample for every 2.5 acres or less. G9217, Should I grid sample my field? Method When creating a soil-sampling plan for fields and farms, the objective is to divide fields into areas that you expect to have similar characteristics or you are likely to manage similarly. G9217, How should I divide my fields? The best approach is to travel across the entire area to be sampled in a zigzag pattern randomly selecting spots to take a core (Figure 1). G9217, How to collect a soil sample This method of sampling is typically used when a farmer uses variable rate technology to apply fertilizers or lime. G9217, Should I grid sample my field? Grid sampling is most justified on high value and high yielding soils, particularly when you anticipate significant variations in soil test levels including low testing areas within a field. It can also be useful the first time you sample the soil in a field with an unknown history. G9217, Should I grid sample my field? Depth Sampling depth is 6 to 7 inches for most objectives. G9217, How to collect a soil sample A separate sample from 0 to 2 inches should be taken in long-term no-till fields to monitor surface pH. G9217, How to collect a soil sample Cores Your objective is to collect from 10 to 20 cores from the area to be sampled (Figure 1). G9217, How to collect a soil sample Take 15 to 20 cores on fields with a history of manure, banded fertilizer applications and other expected sources of variation. Fewer cores (10 to 15) are needed on uniform fields with a history of broadcast fertilization. G9217, How to collect a soil sample On fields where the location of injection bands for fertilizer or manure is known, the objective is to take 30 cores using the following method: G9217, Sampling Fields After Banded Fertilizer Applications Laboratory and analysis Be sure to use a lab that has been accredited by Missouri Soil Testing Association (MSTA). G9217, Submitting your soil samples Field identifiers Label the sample with field and subfield names. G9217, Submitting your soil samples Sources MU Extension G9217, Soil Sampling Hayfields and Row Crops (PDF, CAFO operator curriculum copy) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
MontanaUnited StatesMontana only. Other states set their own rules.	Routine soil fertility samplingMontana State University Extension soil sampling advice	Season Late fall to mid-spring for nitrogen. If sampled in fall above about 60 lb N/acre on soils under two feet deep, sample again in spring.	Not specified	Grid for immobile nutrients, manure or high fertilizer history, or merged fields; zones for nitrogen, organic matter and pH, unknown history or yield linked to landscape. Uniform fields sampled at random. Georeference sampling points and return to them.	Annual crops: 6 inches for most tests, at least 2 feet for nitrogen. Pasture and forage: 12 inches.	Ten subsamples per composite is a reasonable average; 12 per field or zone for plus or minus 25 percent accuracy at 90 percent confidence.	Official guidanceMSU Extension, The Soil Scoop: Soil Testing, Getting a Good Sample (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Montana fields from Montana State University Extension. Not law. Laboratory and analysis Olsen phosphorus test, the basis of Montana P guidelines. Ask whether the lab is enrolled in a proficiency testing program; stay with a reliable lab in later years. Field identifiers Georeference sampling points with GPS; keep records of sampling locations and timing. In force from Under review Legal text MSU Extension, The Soil Scoop: Soil Testing, Getting a Good Sample (September 2025), and MontGuide MT200803AG, Soil Sampling Strategies (revised September 2017) The wording in the source Timing Therefore, sampling in late fall to mid-spring is recommended to best capture growing season N availability. Soil Scoop, Timing If fall nitrate levels are very high (e.g., greater than about 60 lb N/acre) and soil depth is less than two feet, a second sampling in spring is strongly suggested because there is a high likelihood of overwinter nitrate losses. Soil Scoop, Timing Method Grid sampling is good for fields with a history of manure or high fertilizer levels (especially P and K), and small fields merged to form a larger field. Soil Scoop, Location Zone based sampling is suggested for fields with unknown or long cropping history, historically low levels of fertilization, no manure applications, and high with-in field variability or a relationship of yield to landscape. Soil Scoop, Location Uniform fields can be randomly sampled throughout the entire field. MontGuide MT200803AG, Random Sampling All sampling points should be georeferenced with a global positioning system (GPS) receiver and sampled in the same locations in subsequent years to track soil nutrient variation in a field, to see long-term trends, and to guide fertilizer application location. MontGuide MT200803AG, Types of Sampling Depth Pasture and forage get sampled to 12-inch depth, and annual crops to 6-inch for most characteristics and at least to 2-foot depth for N. Soil Scoop, Depth Cores Ten subsamples per composite sample is a reasonable average. More subsamples require more time, but improve accuracy. Soil Scoop, Number if an accuracy level of ± 25% is deemed sufficient at a 90% confidence, then 12 subsamples per field (or zone) should be collected, composited and analyzed for nitrogen, phosphorus, and potassium. MontGuide MT200803AG, Number of Subsamples Laboratory and analysis For example, soil P levels in Montana soils are best tested with the Olsen rather than Bray or Mehlich tests, which are not suitable for soil pH greater than 6. Soil Scoop, Lab Selection Also, Montana’s P fertilization guidelines are based on Olsen P values. Soil Scoop, Lab Selection Ask if the lab is enrolled in a ‘proficiency’ testing program. Soil Scoop, Lab Selection If a lab is reliable, stay with the same lab in subsequent years, because soil test results and recommendations can vary greatly among labs. Soil Scoop, Lab Selection Field identifiers Keep records of sampling locations and timing. Soil Scoop, Location All sampling points should be georeferenced with a global positioning system (GPS) receiver MontGuide MT200803AG, Types of Sampling Sources MSU Extension, The Soil Scoop: Soil Testing, Getting a Good Sample (PDF) Guidance MSU Extension MontGuide MT200803AG, Soil Sampling Strategies (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
NebraskaUnited StatesNebraska only. Other states set their own rules.	Soil phosphorus and nitrogen tests on manure application fieldsLivestock Waste Control Regulations, nutrient management plan	Repeat Phosphorus: before the first manure application, then at least once every 5 years while the field is used Repeat Nitrogen: before the first manure application, then at least annually while the field is used	Not specified	Soil sampling procedures and depths set out in the nutrient management plan. University of Nebraska guidelines may be used; the Department may approve alternatives.	Not specified	Not specified	ConditionalTitle 130, Livestock Waste Control Regulations (effective 23 September 2026)
Who it applies to, the exact wording and every source Who it applies to Livestock operations applying for a permit under Title 130, for each field used to land apply manure, litter or process wastewater. Laboratory and analysis Soil analytic methods set out in the nutrient management plan. University of Nebraska guidelines may be used; the Department may approve alternatives. In force from 23 September 2026 Legal text Nebraska Administrative Code, Title 130, Livestock Waste Control Regulations, Chapter 14, sections 001.10E and 001.11 The wording in the source Timing Application site soils for phosphorus content before the initial application of manure, litter, or process wastewater and then at least once every five years thereafter if used for application; Title 130, Ch. 14, 001.11C Application site soils for nitrogen content before the initial application of manure, litter, or process wastewater, and then sample and analyze at least annually thereafter if used for application; Title 130, Ch. 14, 001.11B Method land application area soil sampling procedures including sampling depths, soil analytic methods Title 130, Ch. 14, 001.10E University of Nebraska guidelines for sampling and analysis may be used. The Department may approve alternate methods as appropriate; Title 130, Ch. 14, 001.11E Who it applies to Each applicant for a permit under these regulations shall submit a nutrient management plan that includes at a minimum the following information as applicable: Title 130, Ch. 14, 001 For each field or field segment used for land application area: Title 130, Ch. 14, 001.10 Laboratory and analysis University of Nebraska guidelines for sampling and analysis may be used. The Department may approve alternate methods as appropriate; Title 130, Ch. 14, 001.11E In force EFFECTIVE 09-23-2026 Title 130, cover page Sources Title 130, Livestock Waste Control Regulations (effective 23 September 2026) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
NebraskaUnited StatesNebraska only. Other states set their own rules.	Routine soil fertility samplingNebraska Extension sampling advice	Season Late fall or early winter, except for nitrate testing on coarse-textured soils. Where nitrate may have leached over winter or spring, spring sampling before planting is the preferred option.	Fields or areas within fields no larger than 40 acres (16.19 ha)	Random cores within representative areas for a uniform rate. Management zones or a grid with known sample locations for variable rate.	0 to 8 inches (0 to 20.32 cm) for pH, lime need, organic matter, P, K, S and Zn. Nitrate: subsurface cores to 3 feet (91.44 cm), 2 feet (60.96 cm) at minimum.	10 to 15 random surface cores per 40-acre area. Six to eight subsoil cores for nitrate.	Official guidanceNebraska Extension, G1740 Guidelines for Soil Sampling
Who it applies to, the exact wording and every source Who it applies to Advice for Nebraska fields from the University of Nebraska-Lincoln Extension. Not law. In force from Under review Legal text Nebraska Extension, Guidelines for Soil Sampling (G1740) The wording in the source Timing Late fall or early winter is a good time for soil sampling, except for testing nitrate-nitrogen on coarse-textured soils. G1740, Time of Sampling If leaching loss of nitrate-nitrogen in the root zone is suspected due to winter or spring precipitation, re-sample the field. Spring sampling prior to planting is the preferred option. G1740, Time of Sampling Area per sample The University of Nebraska–Lincoln recommends that samples represent fields or areas within fields no larger than 40 acres. G1740, Collect Soil Cores Method For uniform fertilizer application, collect soil samples randomly within representative areas of the field. If variable rate fertilizer application is anticipated, sample either in predefined management zones or in a grid pattern with known sample locations. G1740, Determine Sampling Approach Depth In Nebraska, soil test correlation and calibrations for these tests are based on surface samples collected from 0-8 inches. G1740, Select Proper Sampling Depth Surface samples are used to determine soil pH, lime need, organic matter, phosphorus, potassium, sulfur and zinc. G1740, Select Proper Sampling Depth To accurately predict nitrate-nitrogen in the root zone, subsurface samples should be collected to a depth of 3 feet. A 2-foot sample is the minimum sampling depth recommended for nitrate-nitrogen G1740, Select Proper Sampling Depth Cores Acceptable measurement of the average nutrient status in a 40-acre area can be obtained with 10 to 15 randomly collected surface cores and six to eight subsoil cores for nitrate-nitrogen analysis. G1740, Collect Soil Cores Within each of the three management zones in Figure 2b, 10-15 cores should be collected and composited into a sample representing each zone. G1740, Figure 2 caption Sources Nebraska Extension, G1740 Guidelines for Soil Sampling Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
NevadaUnited StatesNevada only. Other states set their own rules.	Routine soil fertility samplingUniversity of Nevada, Reno Extension sampling advice	Repeat Every 2 to 3 years for most crops. Before each crop for high-value cash crops. Sandy soils every 2 to 3 years, clay soils every 3 to 4 years. Every year where earlier tests showed levels too high or too low. Season After harvest and before planting the next crop, around the same month each year Wait Avoid sampling soon after fertilizer or manure applications	Not specified	Divide the field into similar units by soil, slope, drainage, erosion and history. Random cores in a zigzag pattern in each unit; a simple random pattern on uniform fields.	15 cm (6 inches) for shallow-rooted crops, 30 cm (12 inches) for deep-rooted crops. In some cases on light-textured soils where nutrients leach, separate deeper samples from 15 to 60 cm (6 to 24 inches) for available nitrogen and sulfur.	Two or three cores per acre in each unit. At least 15 to 20 cores on uniform fields.	Official guidanceUniversity of Nevada, Reno Extension, FS-19-17
Who it applies to, the exact wording and every source Who it applies to Advice for Nevada growers from the University of Nevada, Reno Extension. Not law. In force from Under review Legal text University of Nevada, Reno Extension, Know the Status of Your Soils Before You Plant (FS-19-17) The wording in the source Timing Generally, soil should be sampled every two to three years for most crops. However, for high-value cash crops, soil should be sampled and tested before each crop is planted. FS-19-17, Time and frequency of soil testing it is recommended that sandy soils be sampled and tested every two to three years and clay soils be tested every three to four years. FS-19-17, Time and frequency of soil testing Soil should also be re-tested every year if nutrient levels are too high or low in previous tests to determine the changes in nutrient levels. FS-19-17, Time and frequency of soil testing it is recommended to sample around the same month of the year to reduce seasonal variations in soil test records. In general, the most important time to test soil is after harvest and before planting of a subsequent crop. FS-19-17, Time and frequency of soil testing Soil sampling soon after fertilizer or manure applications should be avoided. FS-19-17, Soil sample collection Method Soil samples should be collected by dividing the field into similar units or blocks based upon differences in the soil. These differences could be in color, soil types, slope, drainage, degree of erosion, prior management, different crop or manure history, etc. FS-19-17, Soil sample collection For uniform fields, a simple random pattern across the field should be used to collect at least 15 to 20 soil cores to equal depths. FS-19-17, Soil sample collection Depth Then, dig down to a plough depth of 15 cm (6 inches) for shallow-rooted crops and 30 cm (12 inches) for deep-rooted crops (Figure 5). FS-19-17, Basic steps in light-texture soils, where excessive leaching of nutrients occurs, separate deeper samples, down to 15-60 cm (6-24 inches), should be collected and analyzed to determine available nitrogen and sulfur in some cases FS-19-17, Basic steps Cores Several random samples should be collected from each area of each unit or block (two or three subsamples per acre) in a zigzag pattern (Figure 4). FS-19-17, Soil sample collection For uniform fields, a simple random pattern across the field should be used to collect at least 15 to 20 soil cores to equal depths. FS-19-17, Soil sample collection Sources University of Nevada, Reno Extension, FS-19-17 Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
New HampshireUnited StatesNew Hampshire only. Other states set their own rules.	Soil test for corn, forage, pasture and hayUNH Extension soil testing service instructions	Not specified	Not specified	A sample representative of the area to be advised on. Keep out areas with an obvious difference in soil type, drainage or plant growth.	6 to 8 inches (15.24 to 20.32 cm) for row crops and alfalfa. 4 to 6 inches (10.16 to 15.24 cm) for deep grass and pastures. 2 to 4 inches (5.08 to 10.16 cm) for no-till fields.	15 to 20 locations per field, combined	Official guidanceUNH Cooperative Extension, Soil Testing Form: Corn, Forage, Pasture and Hay (PDF)
Who it applies to, the exact wording and every source Who it applies to Instructions for New Hampshire farm samples sent to the University of New Hampshire Extension lab. Not law. In force from Under review Legal text UNH Cooperative Extension, Soil Testing Form: Corn, Forage, Pasture and Hay, sampling instructions The wording in the source Method The soil sample should be representative of the area for which you want recommendations. Avoid areas that have an obvious difference in soil type, drainage, or plant growth. Form page 2, Sampling instructions Depth Each sample should be taken from a depth of 6-8” for row crops Form page 2, Sampling instructions (continues "and alfalfa") 4-6” for deep grass and pastures and 2-4” for no-till fields. Form page 2, Sampling instructions Cores Take samples from 15-20 locations throughout the field and combine in a bucket. Form page 2, Sampling instructions Sources UNH Cooperative Extension, Soil Testing Form: Corn, Forage, Pasture and Hay (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
New JerseyUnited StatesNew Jersey only. Other states set their own rules.	Soil test for field, vegetable, fruit and nursery cropsRutgers Soil Testing Laboratory sampling procedure	Season Easiest when soil moisture is suitable for plowing	Not specified	Vertical slices or cores mixed into one representative sample per sampling area. Separate samples for separate areas.	Surface to 6 to 8 inches (15.24 to 20.32 cm)	11 to 15 locations within the sampling area	Official guidanceRutgers Cooperative Extension, Commercial Farm and Nursery Soil Testing
Who it applies to, the exact wording and every source Who it applies to Instructions for New Jersey growers sending samples to the Rutgers Soil Testing Laboratory. Not law. In force from Under review Legal text Rutgers Cooperative Extension, Commercial Farm and Nursery Soil Testing, Sampling Procedure The wording in the source Timing The soil is easier to sample when its moisture condition is suitable for plowing. Sampling Procedure Method Mix the subsamples of a sampling area together in the container, breaking up large clumps. The goal is to provide a representative sample. Sampling Procedure Repeat for any separate areas that you wish to have tested. Sampling Procedure Depth Use a trowel, spade, auger, or soil tube to obtain thin vertical slices or cores of soil from the surface to a depth of 6 – 8". Sampling Procedure Cores Repeat this procedure at 11 – 15 locations within the sampling area, placing the subsamples together in the container. Sampling Procedure Sources Rutgers Cooperative Extension, Commercial Farm and Nursery Soil Testing Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
New MexicoUnited StatesNew Mexico only. Other states set their own rules.	Annual soil sampling of dairy land application fieldsGround water protection, supplemental permitting requirements for dairy facilities (Dairy Rule)	Repeat Annually on every field that has received wastewater or stormwater, cropped or fallow Season Before the first wastewater application on a new field; an initial event on every field in the first year of each permit term	Not specified	One composite per field from cores taken at random throughout the field; a separate composite for each soil texture.	Three composites per field: 0 to 12 inches (0 to 30.48 cm), 12 to 24 inches (30.48 to 60.96 cm) and 24 to 36 inches (60.96 to 91.44 cm)	15 cores per composite	Conditional20.6.6 NMAC (New Mexico Administrative Code)
Who it applies to, the exact wording and every source Who it applies to Dairy facilities with a discharge permit and a land application area: every field that has received or is receiving wastewater or stormwater, and every field in the first year of each permit term. Laboratory and analysis pH, EC, sodium, calcium and magnesium on a saturated paste extract; phosphorus by Olsen sodium bicarbonate; nitrate by 2 molar KCl extract; methods under 20.6.6.24 NMAC. Field identifiers A map showing the fields and the sampling locations within each field, submitted with the results. In force from 16 June 2015 Legal text 20.6.6 NMAC, Ground Water Protection: Supplemental Permitting Requirements for Dairy Facilities, 20.6.6.25 NMAC, Subsections K and L The wording in the source Timing Beginning in the year following the initial soil sampling required by this section, the permittee shall collect annual soil samples from each field within the land application area that has received or is actively receiving wastewater or stormwater. 20.6.6.25.L NMAC For those fields that have never before received wastewater, the permittee shall collect soil samples immediately before initial wastewater application and annually thereafter. 20.6.6.25.L NMAC Once a field has received wastewater it shall be sampled annually regardless of whether the field is cropped, remains fallow, or has recently received wastewater or stormwater. 20.6.6.25.L NMAC A permittee shall collect composite soil samples from each field within the land application area for the first soil sampling event during the first year following the effective date of the discharge permit. 20.6.6.25.K NMAC Method Each surface and sub-surface soil sample shall consist of a single composite of 15 soil cores collected randomly throughout each field. Should a field consist of different soil textures (i.e., sandy and silty clay), a composite soil sample shall be collected from each soil texture within each field. 20.6.6.25.L(1) NMAC Depth One surface composite soil sample (first-foot) and two sub-surface composite soil samples (second-foot and third-foot) shall be collected from each field. 20.6.6.25.L NMAC Surface soil samples (first-foot) shall be collected from a depth of 0 to 12 inches. 20.6.6.25.L(2) NMAC Each second-foot sub-surface soil sample shall be collected from a depth of 12 to 24 inches. 20.6.6.25.L(3) NMAC Each third-foot sub-surface soil sample shall be collected from a depth of 24 to 36 inches. 20.6.6.25.L(4) NMAC Cores Each surface and sub-surface soil sample shall consist of a single composite of 15 soil cores collected randomly throughout each field. 20.6.6.25.L(1) NMAC Who it applies to ADDITIONAL MONITORING REQUIREMENTS FOR DAIRY FACILITIES WITH A LAND APPLICATION AREA: 20.6.6.25 NMAC, heading Beginning in the year following the initial soil sampling required by this section, the permittee shall collect annual soil samples from each field within the land application area that has received or is actively receiving wastewater or stormwater. 20.6.6.25.L NMAC Laboratory and analysis pH, electrical conductivity, sodium, calcium, and magnesium shall be analyzed using a saturated paste extract in accordance with the analytical methodology required by Subsection B of 20.6.6.24 NMAC. Phosphorus shall be analyzed using the Olsen sodium bicarbonate method 20.6.6.25.L(7) NMAC Nitrate as nitrogen shall be analyzed by a 2 molar KCl extract 20.6.6.25.L(7) NMAC Field identifiers The permittee shall submit the analytical results and a map showing the fields and the sampling locations within each field to the department in the monitoring report due by May 1. 20.6.6.25.L(8) NMAC In force EFFECTIVE DATE: 01/31/2011, unless a later date is cited at the end of a section. 20.6.6.5 NMAC [20.6.6.25 NMAC – N, 01/31/2011; A, 12/31/2011; A, 06/16/2015] 20.6.6.25 NMAC, history note Sources 20.6.6 NMAC (New Mexico Administrative Code) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
New MexicoUnited StatesNew Mexico only. Other states set their own rules.	Routine soil fertility samplingNMSU Cooperative Extension sampling advice	Repeat Every year before the crop season; at least every other year	Divide crop fields larger than 25 acres (10.12 ha) into separate sampling sections	One sample per management zone: an area treated the same for water, fertilizer and yield potential. Divide by yield history, slope, weed pressure and soil type.	Untilled ground (direct-seeded fields, orchards, vineyards): 6 to 8 inches (15.24 to 20.32 cm). Tilled fields: 12 inches (30.48 cm).	10 to 15 subsamples from the same depth per sample	Official guidanceNMSU Guide A-146, Recommended Analyses for New Mexico Soils
Who it applies to, the exact wording and every source Who it applies to Advice for New Mexico farms from New Mexico State University Cooperative Extension. Not law. Laboratory and analysis Labs in the North American Proficiency Testing Program are suggested. For New Mexico soils, pH on the saturated paste. In force from Under review Legal text New Mexico State University, Guide A-146, Recommended Analyses for New Mexico Soils The wording in the source Timing It is recommended to test your soil every year before the crop season to assess its chemical and nutrient status. If that is not possible, then at least every other year. Guide A-146, Introduction Area per sample Crop fields larger than 25 acres should be divided into separate sampling sections to capture differences within the field. Guide A-146, Collecting a Sample from the Field Method Samples should be taken from areas that can be treated as distinct units (management zones). Guide A-146, Collecting a Sample from the Field When deciding how to divide a field, consider historical yield variation along with factors like slope, weed pressure, and soil type. Guide A-146, Collecting a Sample from the Field The recommended number of subsamples ensures that the sample is representative of a “management zone.” This area may be treated the same for watering, fertilizer application, and yield potential. Guide A-146, Collecting a Sample from the Field Depth Areas that are not tilled, such as direct-seeded fields, orchards, vineyards, turfgrass, and perennial gardens, should be sampled to a depth of 6 to 8 inches. Any area that has been tilled, such as annual gardens, conventionally tilled production fields, or similar areas, should be sampled to a depth of 12 inches. Guide A-146, Collecting a Sample from the Field Cores It usually takes 10 to 15 subsamples taken to the same depth and combined into one sample in order to be confident in the soil test results from any given lab. Guide A-146, Collecting a Sample from the Field Laboratory and analysis Consider using laboratories that participate in the North American Proficiency Testing Program (Table 1). Guide A-146, Laboratories For New Mexico soils, pH should be determined on the saturated paste (pHs), which best reflects field conditions. Guide A-146, What Analyses to Request, pH Sources NMSU Guide A-146, Recommended Analyses for New Mexico Soils Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
New YorkUnited StatesNew York only. Other states set their own rules.	Soil sampling for field cropsCornell Nutrient Management Spear Program, Agronomy Fact Sheet Series	Repeat At least once every 2 to 3 years Season Best in fall after harvest of the main crop; spring or summer also possible. Sample around the same month each year. Wait 5 to 6 weeks after fertilizer or manure, or sod termination, for pH, general fertility and the soil nitrogen test	Generally 15 acres (6.07 ha) or less per sample. Grid cells often 0.5 to about 6 acres.	Zigzag across the field when one sample represents the whole field. Grid sampling for larger fields and zone management; grid results can define management zones that are sampled from then on.	Conventional tillage 0 to 8 inches (0 to 20.32 cm). Pasture 0 to 6 inches (0 to 15.24 cm). No-till or minimum till: 0 to 1 inch (0 to 2.54 cm) for pH and 0 to 6 inches (0 to 15.24 cm) for nutrients.	About two cores per acre (field acres times 2), at least 10 to 15 on smaller fields. Grid cells and zones: an average of two cores per acre.	Official guidanceCornell Agronomy Fact Sheet #1, Soil Sampling for Field Crops (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for New York field crops from Cornell University College of Agriculture and Life Sciences. Not law. In force from Under review Legal text Cornell University, Agronomy Fact Sheet #1, Soil Sampling for Field Crops (2020) The wording in the source Timing It is recommended to take soil samples at least once every 2 to 3 years. Fact Sheet #1, Establish a Regular Sampling Time Soil samples are best taken in the fall after harvest of the main season crop but can also be taken in the spring or summer. Fact Sheet #1, Establish a Regular Sampling Time Consistently sampling around the same month of the year will help reduce seasonal variation in soil tests Fact Sheet #1, Establish a Regular Sampling Time For soil pH, general soil fertility, and determination of soil nitrogen supply potential with the Illinois Soil Nitrogen Test, do not sample within 5-6 weeks of fertilizer or manure application or sod termination. Fact Sheet #1, Obtain a Representative Sample Area per sample Generally, each sample should represent 15 acres or less, and separate samples should be collected from areas with different crop history, fertility management, crop growth, slope, etc. Fact Sheet #1, Obtain a Representative Sample Grid cell size often ranges from 0.5 to about 6 acres. Fact Sheet #1, Obtain a Representative Sample Method If a sample is needed to represent the entire field, and no prior information is available, take samples along a zig-zag pattern through the field. Fact Sheet #1, Obtain a Representative Sample Grid sampling may be used for larger fields and when zone-based management is desired. Fact Sheet #1, Obtain a Representative Sample Grid cells can be sampled separately over time or used to develop larger management zones, which can then be sampled separately in future years. Fact Sheet #1, Obtain a Representative Sample Depth For field crops, under conventional tillage, sample the top 0-8 inches (Figure 1). Fact Sheet #1, Sample the Proper Depth For pastures, it is recommended to sample the top 0-6 inches. For no-till or minimum-till cropping systems, take two samples: one for pH from the 0-1 inch depth and another from the 0-6 inch depth for nutrient analyses. Fact Sheet #1, Sample the Proper Depth Cores For best results, multiply the total acreage of the field by 2 to know roughly how many cores to combine across the field, with a 10-15 core minimum for smaller fields. Fact Sheet #1, Obtain a Representative Sample Each management zone should be sampled at an intensity that targets an average of two soil cores per acre or a full cup of soil to subsample. Fact Sheet #1, Obtain a Representative Sample Sources Cornell Agronomy Fact Sheet #1, Soil Sampling for Field Crops (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
North CarolinaUnited StatesNorth Carolina only. Other states set their own rules.	Routine soil fertility samplingNC State Extension SoilFacts	Repeat Coastal plain: every 2 to 3 years. Piedmont and mountains: once every 4 years is usually enough. Season 3 to 6 months before planting, at the same time every year if possible. Perennial or sod crops: 3 to 4 months before establishing the crop or applying lime or fertilizer.	No more than about 20 acres (8.09 ha) per sample, even where the soil looks uniform	Cores at random locations through one field or area of one soil type or condition. A separate sample for each area that differs in slope, color, drainage or texture and can be fertilized separately.	Field crops: plow depth, usually about 8 inches (20.32 cm). Perennial crops being maintained (fescue, alfalfa, turf): 4 inches (10.16 cm).	About 15 to 20 cores per sample	Official guidanceNC State Extension, AG-439-30, Careful Soil Sampling
Who it applies to, the exact wording and every source Who it applies to Advice for North Carolina farms from NC State Extension, written with the state soil testing laboratory. Not law. In force from Under review Legal text NC State Extension, Careful Soil Sampling: The Key to Reliable Soil Test Information (AG-439-30, 2022) The wording in the source Timing Collect samples three to six months before planting time. AG-439-30, When to Take Samples If possible, try to collect your samples at the same time every year. AG-439-30, When to Take Samples Sample the soil from perennial or sod-crop areas three to four months before establishing the crop or applying lime or fertilizer. AG-439-30, When to Take Samples If your farm is in the coastal plain region, it is best to test the soil every two to three years. AG-439-30, How Often to Sample In these areas, soil testing once every four years is usually sufficient. AG-439-30, How Often to Sample (piedmont and mountain regions) Area per sample A sample should include cores from no more than about 20 acres even if the soil appears to be uniform over a larger area. AG-439-30, Where to Take Samples Method Every soil sample you submit for testing should consist of about 15 to 20 cores taken at random locations throughout one field or area. AG-439-30, Where to Take Samples If the field you are sampling contains areas that are obviously different in slope, color, drainage, and texture and if those areas can be fertilized separately, submit a separate sample (consisting of 15 to 20 cores) for each area (Figure 1). AG-439-30, Where to Take Samples Depth For areas in which field crops are grown, collect samples to the same depth that the field is plowed (usually about 8 inches) AG-439-30, How to Collect a Good Sample For fields when perennial crops such as fescue, alfalfa, and turf are being maintained, samples taken to a depth of 4 inches will best represent the crop AG-439-30, How to Collect a Good Sample Cores Every soil sample you submit for testing should consist of about 15 to 20 cores taken at random locations throughout one field or area. AG-439-30, Where to Take Samples Sources NC State Extension, AG-439-30, Careful Soil Sampling Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
North DakotaUnited StatesNorth Dakota only. Other states set their own rules.	Soil sampling for fertilizer recommendations, including nitrateNDSU Extension sampling advice	Season Nitrate samples may be taken right after any grain harvest. Sample for K at the same time each year.	Where grid sampling is used: one sample per acre (0.40 ha). Coarser grids, such as one sample per 2.5 acres, are inadequate in North Dakota. The guide sets no area for zone samples.	Zone sampling, with zones built from at least two tools such as crop canopy imagery, soil EC sensors, multiyear yield maps and elevation. A systematic unaligned grid only in areas with large manure applications or fields with large P and K buildup applications.	0 to 6 inches (0 to 15.24 cm) for pH, P, K, Zn, Cu, Mn. 0 to 2 feet (0 to 60.96 cm) for nitrate-N and chloride, best split at 6 inches. No-till: 0 to 2 inches (0 to 5.08 cm) separately from 2 to 6 inches.	Eight to 10 cores at random within each zone	Official guidanceNDSU Extension, SF990 Soil Sampling as a Basis for Fertilizer Application
Who it applies to, the exact wording and every source Who it applies to Advice for North Dakota fields from North Dakota State University Extension. Not law. In force from Under review Legal text NDSU Extension, Soil Sampling as a Basis for Fertilizer Application (SF990, revised September 2023) The wording in the source Timing Soil samples for nitrate-N analysis may be taken immediately after any grain harvest. SF990, Sample Collection Timing obtaining soil samples for K analysis at the same time each year is important. SF990, Sample Collection Timing Area per sample Grid sampling can reveal soil test value patterns, provided the sampling is conducted in a dense grid of one sample per acre (Franzen and Peck, 1995). SF990, Sampling for Within-field Soil Test Values Extensive research in North Dakota has indicated that any grid density less than this, such as one sample per 2.5 acres, is inadequate to reveal actual soil test patterns in fields. SF990, Sampling for Within-field Soil Test Values Method Grid sampling is recommended in North Dakota only in areas with large manure applications or in fields that have received large amounts of buildup P and K fertilizers. SF990, Sampling for Within-field Soil Test Values Zones should be developed using at least two tools (Franzen et al., 2011). SF990, Zone Sampling Aerial imagery from piloted aircraft or drones … satellite imagery of growing crops … soil electrical conductivity sensors … multiyear yield maps … topography developed from subinch accuracy GPS elevation … may be used to help develop zones for use in soil sampling. SF990, Zone Sampling The pattern of grid sampling should be a systematic, unaligned grid as illustrated in Figure 7. SF990, Sampling for Within-field Soil Test Values Depth For soil pH, P, K, Zn, copper (Cu) and manganese (Mn), sampling the 0- to 6-inch depth is required because that is the depth of sampling related to crop response in this region. SF990, Depth of Sampling, Nutrients For soil nitrate-N and chloride, a 0- to 2-foot core is required. Instead of analyzing just one 0- to 2-foot core, dividing the core into a 0- to 6-inch core and a 6- to 24-inch core, and analyzing each one separately would be instructive. SF990, Depth of Sampling, Nutrients Therefore, in fields under no-till systems, the 0- to 2-inch depth should be separated and analyzed separately for soil pH, P and K in addition to analyzing soil at the 2- to 6-inch depth. SF990, Tillage System Cores Generally, eight to 10 cores should be obtained randomly within a zone for the value to be reproducible. SF990, Sampling Within a Zone Sources NDSU Extension, SF990 Soil Sampling as a Basis for Fertilizer Application Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
OhioUnited StatesOhio only. Other states set their own rules.	Soil sampling to develop nutrient recommendationsOhio State University Extension, Ohioline fact sheets	Not specified	No sample zone over 25 acres (10.12 ha). Grid option: one point per 2.5 acres (360 by 360 feet).	Systematic grid sampling, or management zones from yield maps, management history and other data; zigzag through each zone. Georeferenced points help track trends.	8 inches (20.32 cm), the depth most soil tests are calibrated to. No-till: a 0 to 2 inch (0 to 5.08 cm) sample for pH may help.	At least 15 cores per composite from 25 acres or less; 20 to 25 after banded fertilizer. Zones: 10 to 15 cores. Grid points: 8 cores within a 10-foot circle.	Official guidanceOhioline AGF-513, Soil Sampling to Develop Nutrient Recommendations
Who it applies to, the exact wording and every source Who it applies to Advice for Ohio fields from Ohio State University Extension. Not law. Laboratory and analysis Ask whether the lab follows Recommended Chemical Soil Test Procedures for the North Central Region. In force from Under review Legal text Ohio State University Extension, Soil Sampling to Develop Nutrient Recommendations (AGF-513, 2012) The wording in the source Area per sample Even after careful consideration to the field landscape and variability, no individual sample zone should represent more than 25 acres. AGF-513, Taking a Representative Soil Test A 360 X 360 foot grid results in a systematic sampling pattern for each 2.5 acres in a field. AGF-513, Systematic Grid Sampling Method Systematic grid sampling and zone management are the two primary methods of dividing field areas for soil sampling using precision applications (Table 2). AGF-513, Soil Sampling with Precision Agriculture Follow a zigzag pattern over the sample area when zone sampling (Figure 2). AGF-513, Taking the Soil Cores Georeferenced sample points may give a better opportunity to compare sample trends over time by returning to near the same point in future years. AGF-513, Zone Management Depth Most soil tests are calibrated using an 8-inch sampling depth, which corresponds to the plow depth. Management in no-till systems may benefit from a 0–2 inch sample for pH, especially where pH-sensitive herbicides are used. AGF-513, Taking the Soil Cores Cores For a standard soil sample, take at least 15 sample cores from each field area of 25 acres or less into one composite sample. AGF-513, Taking the Soil Cores If the field has a history of banded fertilizer applications, increase the number of samples to 20–25 cores. AGF-513, Taking the Soil Cores Sample points should be taken randomly with 10–15 cores per sample area of up to 25 acres. AGF-513, Zone Management Soil samples are collected at each sample point within a 10-foot diameter circle, with two cores pulled from each quadrant, for a total of eight cores. AGF-513, Systematic Grid Sampling Laboratory and analysis Standards for laboratory procedure and extraction solutions have been established by land-grant universities in the publication Recommended Chemical Soil Test Procedures for the North Central Region. It is a good practice to ask if the laboratory utilizes these procedures in their analysis process. AGF-513, Sending the Sample to the Testing Lab Sources Ohioline AGF-513, Soil Sampling to Develop Nutrient Recommendations Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
OklahomaUnited StatesOklahoma only. Other states set their own rules.	Soil test on poultry waste land application areasOklahoma Registered Poultry Feeding Operations Act, nutrient management plan	Repeat Operations in a non-nutrient-limited watershed and non-nutrient-vulnerable groundwaters: at least once every 3 years on each land application area Repeat Operations in a nutrient-limited watershed and nutrient-vulnerable groundwater: every year on each land application area, before the first application of the calendar year Result valid Analysis data must be dated before the land application and kept for at least 6 years	Not specified	Not specified	Not specified	Not specified	ConditionalOklahoma Registered Poultry Feeding Operations Act (Title 2 O.S.), text as compiled by the Oklahoma Department of Agriculture, Food, and Forestry, reference date 29 August 2024 (PDF)
Who it applies to, the exact wording and every source Who it applies to Poultry feeding operations under the Act, meaning a property or facility where poultry are confined and fed 45 days or more in any 12 months, crops or other vegetation are not sustained over any part of it in the normal growing season, and over 10 tons of poultry waste are produced a year. Applies to each land application area. Laboratory and analysis Soil pH and plant-available nutrients, at a minimum nitrogen, phosphorus and potassium. In force from Under review Legal text Oklahoma Registered Poultry Feeding Operations Act, Title 2 O.S. Section 10-9.7, Section 10-9.7, subsections F, G and H The wording in the source Timing Every poultry feeding operation located in a non-nutrient-limited watershed and non-nutrient-vulnerable groundwaters shall perform soil testing on each land-application area and poultry waste testing at least once every three (3) years 2 O.S. Section 10-9.7(F) Every poultry feeding operation located in a nutrient-limited watershed and nutrient-vulnerable groundwater shall perform an annual soil test on each land-application area prior to the first application of the calendar year. 2 O.S. Section 10-9.7(G) Soil and poultry waste analysis data shall be retained by the poultry feeding operation for a minimum of six (6) years. 2 O.S. Section 10-9.7(H)(1) All soil and poultry waste analysis data shall be dated prior to land application. 2 O.S. Section 10-9.7(H)(2) Who it applies to Every poultry feeding operation shall have a Nutrient Management Plan which shall include at a minimum: 2 O.S. Section 10-9.7(C) All nutrient analysis data for soil and poultry waste testing; 2 O.S. Section 10-9.7(C)(3) poultry have been, are or will be confined and fed or maintained for a total of forty-five (45) days or more in any twelve-month period, 2 O.S. Section 10-9.1(B)(20)(a), definition of poultry feeding operation crops, vegetation, forage growth or post-harvest residues are not sustained in the normal growing season over any portion of the property or facility, and 2 O.S. Section 10-9.1(B)(20)(b) producing over ten (10) tons of poultry waste per year; 2 O.S. Section 10-9.1(B)(20)(c) Laboratory and analysis Soil pH and plant-available nutrients including, at a minimum, nitrogen, phosphorous, and potassium; 2 O.S. Section 10-9.7(F)(1) Sources Oklahoma Registered Poultry Feeding Operations Act (Title 2 O.S.), text as compiled by the Oklahoma Department of Agriculture, Food, and Forestry, reference date 29 August 2024 (PDF) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
OregonUnited StatesOregon only. Other states set their own rules.	Routine soil fertility sampling for farms and gardensOregon State University Extension sampling advice	Repeat Every 2 to 3 years for annual crops, pastures and legumes. Every 3 to 5 years for Christmas trees, fruit and nut trees, berries and grapes. Season Same time of year each time. Western Oregon high-rainfall soils: late summer or fall. Perennial crops: before planting.	Not specified	A separate sample for each area that differs in soil type, topography, crop or management history. Avoid unusual spots.	Surface to about 6 inches (15.24 cm), or to the depth of tillage. Keep the same depth for all future samples.	15 to 20 subsamples per sampling area	Official guidanceOregon State University Extension, EC 628 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice for Oregon farms and gardens from Oregon State University Extension. Not law. In force from Under review Legal text Oregon State University Extension, A Guide to Collecting Soil Samples for Farms and Gardens (EC 628, revised November 2022) The wording in the source Timing In general, test every 2 to 3 years for annual crops, pastures, and legumes, and test every 3 to 5 years for Christmas trees, fruit and nut trees, berries, and grapes. Take samples at the same time of year so results are comparable from year to year. EC 628, How often should I collect a soil sample? Testing these soils in the late summer or fall allows time for these amendments to react with the soil before the following growing season. EC 628, When should I collect my soil sample? (high rainfall areas of western Oregon) the most important time to test the soil is before planting so necessary nutrients can be incorporated into the soil. EC 628, When should I collect my soil sample? (perennial crops) Method The area from which to collect a soil sample may depend on the soil type, topography, crops grown, management history, or all of the above. EC 628, Where should I collect a soil sample? Avoid sampling in small areas where you know that conditions are different from the rest of the field (for example, former manure piles, fertilizer bands, or fence lines). EC 628, Avoid unusual areas Depth For most annual and perennial crops, sample from the surface down to about 6 inches (Figure 5) or to the depth of tillage. EC 628, Take the soil sample to the correct depth Collect samples at the same depth. For example, if you take initial samples at a 6-inch depth, keep that same depth for all future samples EC 628, Take the soil sample to the correct depth Cores Each sample should consist of subsamples taken from 15 to 20 locations within the sampling area (Figure 2). EC 628, Take 15 to 20 subsamples Sources Oregon State University Extension, EC 628 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
PennsylvaniaUnited StatesPennsylvania only. Other states set their own rules.	Soil test for P, K and pH in a nutrient management planNutrient Management Act (Act 38), nutrient management plans	Repeat Every crop management unit at least every 3 years from the date of the last test, once the plan is approved Result valid For the initial plan, tests taken within the previous 3 years are acceptable	Not specified	One soil test per crop management unit: a field, part of a field or group of fields with the same rotation and manure history and similar production capability, managed as one unit.	Not specified	Not specified	Conditional25 Pa. Code Section 83.292
Who it applies to, the exact wording and every source Who it applies to Nutrient management plan operations: concentrated animal operations (8 or more animal equivalent units where animal density exceeds 2 AEUs per acre on an annualized basis), operations that submit a plan voluntarily, and operations required to develop compliance plans under section 506(j) of the Act. Soil tests for every crop management unit. Laboratory and analysis Accurate test procedures; the Penn State recommended procedures in Recommended Soil Testing Procedures for the Northeastern United States (Bulletin 493) may be used, others need Commission approval. The plan lists P, K and pH results, the test date and the lab name. In force from 1 October 2006 Legal text 25 Pa. Code Chapter 83, Subchapter D, Nutrient Management, Section 83.292(e) The wording in the source Timing After the approval of the initial plan, soil tests are required for each crop management unit at least every 3 years from the date of the last test. 25 Pa. Code Section 83.292(e)(4) Soil tests conducted within the previous 3 years prior to submitting the initial plan are acceptable. 25 Pa. Code Section 83.292(e)(2) Method When developing the initial plan, soil tests shall be conducted for each crop management unit on the operation, to determine the level of phosphorus (as P), potassium (as K), and soil pH 25 Pa. Code Section 83.292(e) The portion of cropland, hayland and pasture, including a field, a portion of a field, or group of fields, on an agricultural operation that has a unique management history (same rotation and manure history), similar production capability, and that will be managed uniformly as a distinct unit. 25 Pa. Code Section 83.201, definition of crop management unit Who it applies to NMP operations shall meet the plan requirements of 25 Pa. Code Section 83.261 (the list includes Sections 83.291 to 83.294) CAOs, VAOs and operations required to develop compliance plans under section 506(j) of the act (relating to nutrient management plans). 25 Pa. Code Section 83.201, definition of NMP operation (nutrient management plan operation) Agricultural operations with eight or more animal equivalent units where the animal density exceeds two AEUs per acre on an annualized basis. 25 Pa. Code Section 83.201, definition of CAO (concentrated animal operation) An agricultural operation other than a CAO may voluntarily submit a plan at any time after October 1, 1997. 25 Pa. Code Section 83.261(5) Laboratory and analysis The soil test procedures used must provide accurate test results. The procedures recommended by the Pennsylvania State University and published in Recommended Soil Testing Procedures for the Northeastern United States, Bulletin #493, published by the University of Delaware, may be used to meet this requirement. Other procedures shall be approved by the Commission. 25 Pa. Code Section 83.292(e)(1) The plan must include an appendix containing a summary of the results of the soil test analyses for each crop management unit showing the following: 25 Pa. Code Section 83.292(e)(3) The date of the soil tests and the name of the lab performing the tests. 25 Pa. Code Section 83.292(e)(3)(iv) In force The provisions of this § 83.292 amended June 2, 2006, effective October 1, 2006, 36 Pa.B. 2636. 25 Pa. Code Section 83.292, Source note Sources 25 Pa. Code Section 83.292 Law 25 Pa. Code Section 83.261 Law 25 Pa. Code Section 83.201 (definitions) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
PennsylvaniaUnited StatesPennsylvania only. Other states set their own rules.	Routine soil fertility sampling for cropland and foragePenn State Extension sampling advice	Repeat At least every 3 years, or when the cropping system changes significantly Season Fall is the best time logistically. Before a forage seeding: at least 6 months ahead.	One sample should not represent more than 10 to 20 acres (4.05 to 8.09 ha)	Cores at random over the field, between old crop rows; separate samples from known problem areas.	Plow depth in cultivated fields. No-till: one sample to 6 inches (15.24 cm) and one to 2 inches (5.08 cm). Permanent pasture: 3 to 4 inches (7.62 to 10.16 cm).	At least 15 to 20 spots at random over the field	Official guidancePenn State Extension, Soil Fertility Management for Forage Crops: Pre-establishment
Who it applies to, the exact wording and every source Who it applies to Advice for Pennsylvania fields from Penn State Extension. Not law. In force from Under review Legal text Penn State Extension, Soil Fertility Management for Forage Crops: Pre-establishment (updated August 2025) The wording in the source Timing A regular soil testing program should be followed in fields by sampling at least every three years or when the cropping system in a field significantly changes. Soil Testing The best time to sample from a logistical standpoint is in the fall. However, when establishing a forage crop, soil samples should be collected at least six months prior to establishment to allow for soil pH adjustments, if necessary. Guidelines for Taking a Soil Sample Area per sample One sample should not represent more than 10 to 20 acres. Guidelines for Taking a Soil Sample Method Take cores from at least 15 to 20 spots randomly over the field to obtain a representative sample. Guidelines for Taking a Soil Sample Sample between old crop rows. Avoid old fencerows, dead furrows, and other spots that are not representative of the whole field. Guidelines for Taking a Soil Sample Take separate samples from known problem areas. Guidelines for Taking a Soil Sample Depth Sample to plow depth in cultivated fields. Guidelines for Taking a Soil Sample Take two samples from no-till fields: one to a 6-inch depth for lime and fertilizer recommendations, and one to a 2-inch depth to monitor surface acidity. Guidelines for Taking a Soil Sample Sample permanent pastures to a depth of 3 to 4 inches. Guidelines for Taking a Soil Sample Cores Take cores from at least 15 to 20 spots randomly over the field to obtain a representative sample. Guidelines for Taking a Soil Sample Sources Penn State Extension, Soil Fertility Management for Forage Crops: Pre-establishment Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
South CarolinaUnited StatesSouth Carolina only. Other states set their own rules.	Soil test before land applying animal manureStandards for the Permitting of Agricultural Animal Facilities	Season Each field, before manure application (required) Repeat Each field should be sampled at least once per year (the rule says "should") Season Where manure goes on less than once a year, at least one sample before returning to that field (required)	Not specified	Not specified	Usually 6 to 8 inches (15.24 to 20.32 cm). The rule gives this as the usual depth, not a fixed one.	Not specified	ConditionalSC State Register Document No. 4997, R.61-43 (final, State Register 45/5)
Who it applies to, the exact wording and every source Who it applies to Land where animal manure and other animal byproducts are applied under R.61-43 (Part 100 for swine, Part 200 for other animal facilities). Each field is sampled before manure application, to set the application rate. In force from 28 May 2021 Legal text S.C. Code of Regulations R.61-43, as replaced by State Register Document No. 4997, Sections 100.100.B.9 (swine) and 200.100.B.9 (other animal facilities) The wording in the source Timing Soil sampling (usually 6 to 8 inch depth) shall be conducted for each field prior to manure application to determine the appropriate application rate. R.61-43, 200.100.B.9 Each field should be sampled at least once per year. R.61-43, 200.100.B.9 (same sentence in 100.100.B.9 for swine) If manure application frequency will be less than once per year, then at least one (1) soil sample shall be taken prior to returning to that field for land application. R.61-43, 200.100.B.9 Depth Soil sampling (usually 6 to 8 inch depth) shall be conducted for each field prior to manure application R.61-43, 200.100.B.9 Who it applies to This part applies to all land where animal manure and other animal byproducts are applied. R.61-43, 200.10.B.3 Soil sampling (usually 6 to 8 inch depth) shall be conducted for each field prior to manure application to determine the appropriate application rate. R.61-43, 200.100.B.9 This part applies to all land where swine manure and other swine byproducts are applied. R.61-43, 100.10.B.3 In force 05/28/2021 Effective Date unless otherwise provided for in the Regulation Document No. 4997, History table (cells transcribed) Sources SC State Register Document No. 4997, R.61-43 (final, State Register 45/5) Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
South CarolinaUnited StatesSouth Carolina only. Other states set their own rules.	Routine soil fertility samplingClemson University Agricultural Service Laboratory sampling guidelines	Not specified	One sample per 10 acres or less (4.05 ha) on large areas	Sample separately areas cropped or fertilized differently, or with different soil types or textures.	Cultivated areas: surface to 6 to 8 inches (15.24 to 20.32 cm). Pasture or turf: 2 to 4 inches (5.08 to 10.16 cm).	Sub-samples from at least 12 locations	Official guidanceClemson Agricultural Service Laboratory, Guidelines for Collecting Samples
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university laboratory for South Carolina. Not law. In force from Under review Legal text Clemson University Agricultural Service Laboratory, Guidelines for Collecting Samples The wording in the source Area per sample For large areas, one soil sample should represent 10 acres or less. Soil Samples, item 1 Method Areas cropped or fertilized differently or those with different soil types or textures should be sampled separately. Soil Samples, item 1 Depth Samples from cultivated areas should be taken from the surface to a depth of 6 to 8 inches. Soil Samples, item 2 Samples from pasture or turf should be taken only 2 to 4 inches deep. Soil Samples, item 2 Cores Take sub-samples from at least 12 locations within the sample area. Soil Samples, item 3 Sources Clemson Agricultural Service Laboratory, Guidelines for Collecting Samples Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
South DakotaUnited StatesSouth Dakota only. Other states set their own rules.	Routine soil fertility and nitrate samplingSDSU Extension, Recommended Soil Sampling Methods for South Dakota	Repeat P, K, pH, salts, Ca, Mg and micronutrients every 2 to 3 years. Nitrate every year before non-legume crops. Season Mobile nutrients, nitrate in particular: late fall once soil is below 50 F, winter, or early spring. Most other tests any time of year.	Grid cells no larger than 2.5 acres (1.01 ha)	Whole field composite, a grid of 2.5 acres or less, or directed zone sampling by landscape, yield, imagery or soil conductivity.	0 to 6 inches (0 to 15.24 cm) for P, K, pH, organic matter, soluble salts, zinc, iron, manganese, copper and boron. For mobile nutrients such as nitrate, chloride and sulfur, a 24 inch sample split into 0 to 6 and 6 to 24 inches (15.24 to 60.96 cm).	At least 15 cores for a whole field or a zone. A grid sample is usually 6 to 8 cores.	Official guidanceSDSU Extension P-00132 (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for South Dakota. Not law. In force from Under review Legal text SDSU Extension P-00132, Recommended Soil Sampling Methods for South Dakota (September 2019) The wording in the source Timing In general, soil tests for P, K, pH, soluble salts, calcium (Ca), magnesium (Mg), and micronutrients will change very little from year to year and need to be analyzed only every 2 to 3 years. P-00132 p. 1, When and how often to sample In contrast, levels of NO3-N can change dramatically from year to year and should be analyzed every year prior to planting non-legume crops. P-00132 p. 1, nitrate In summary, a soil sample for most soil tests can be taken anytime during the year. P-00132 p. 2, summary For most mobile nutrients, in particular NO3-N, samples should be taken in late fall (when soil temperatures are below 50° F), in winter, or in early spring. P-00132 p. 2, summary Area per sample the largest grid size that will adequately measure nutrient variability for a field should be no more than 2.5 acres in size. P-00132 p. 5, Grid sampling Method Fields may be divided into smaller parcels or “zones” or sampled as a whole field. P-00132 p. 4, Field sampling methods The field is divided into rectangular grids and a sample is taken from each grid. P-00132 p. 5, Grid sampling Detailed information about a field, such as yield monitor maps, remote sensing imagery, digital soil survey or topographic maps, and/or electrical conductivity data, can all help define nutrient management zones. P-00132 p. 5, Directed sampling Depth A 0-6 inch sample is recommended for P, K, pH, organic matter, soluble salts, zinc (Zn), iron (Fe), manganese (Mn), copper (Cu), and boron (B). P-00132 p. 2, Nutrients A deep sample (24-inch) is recommended for mobile nutrients such as NO3-N, chloride (Cl), and sulfur … P-00132 p. 2, Nutrients It is recommended to separate deep samples (0-24 inch) into two separate samples; one representing the 0-6 inch depth and the other a 6-24 inch depth (Figure 2). P-00132 p. 2, Nutrients Cores taking at least 15 random cores from the field and compositing (mixing) by depth increment P-00132 p. 4, Whole field composite method Each grid sample is usually a composite of 6 to 8 cores. P-00132 p. 5, Grid sampling A field with four landscape zones would have four separate samples, each with a minimum of 15 cores. P-00132 p. 6 Sources SDSU Extension P-00132 (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
TennesseeUnited StatesTennessee only. Other states set their own rules.	Routine soil fertility samplingUT Extension, Soil Testing for Commercial Farmers	Repeat Continuous conventional row crops every 2 to 3 years. Double cropping, continuous no-till corn or cotton, and hay every 2 years. Continuous no-till soybeans only, and pasture, every 3 to 5 years. Tobacco and vegetables every year. Season September to November, or March to April	A composite from an area of no more than 10 acres (4.05 ha). Grids of 2.5 or 5 acres are widely used.	Whole field composite in a zigzag pattern, grid, or zones built from soil type, lime and fertilizer history and yield maps. Sample contrasting areas separately.	6 inches (15.24 cm) for pH, P, K, Ca, Mg, micronutrients and organic matter. 12 inches (30.48 cm) for the corn pre-sidedress nitrate test.	About 20 locations per composite. Six or eight cores per grid sample.	Official guidanceUT Extension W 1194, Soil Testing for Commercial Farmers (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for Tennessee. Not law. In force from Under review Legal text UT Extension W 1194, Soil Testing for Commercial Farmers (9/23) The wording in the source Timing Soil samples can be collected at any time from September to November (fall) or March to April (spring). W 1194, When to sample? Continuous Row Crops (conventional) … every two to three years. W 1194, How often should soils be tested?, item 1 Double-cropping Systems … every two years. item 2 Continuous No-till Soybeans (only) … every three to five years. item 3 Continuous No-till Corn or Cotton … every two years. item 4 Hay Systems … every two years. item 5 High-value Cash Crops (tobacco, vegetables) … annually. item 6 Pasture Crops … every three to five years. item 7 Area per sample subsamples should be collected in a zigzag pattern from an area not to exceed ten acres W 1194, Composite/Whole Field Method A widely used method is to grid fields into two and a half or five acres. W 1194, Grid Method Method The commonly used sampling methods include the composite/whole field, the grid, and the zone. W 1194, The Sampling Method Areas of contrasting soils, problem spots, areas under different management within the same field, or portions of fields where crop response is significantly different should be sampled separately, provided the area can be fertilized separately. W 1194, Composite/Whole Field Method Zones are developed based on knowledge about the field such as soil type, past lime and fertilization histories, yield maps W 1194, Zone method Depth the recommended sampling depth at University of Tennessee is six inches (or 15 cm). W 1194, Sampling Tools and Depths For the corn pre-sidedress nitrate-nitrogen test, collect samples to a depth of twelve inches (or 30 cm). W 1194, Sampling Tools and Depths Cores a composite sample consisting of small portions of soil taken from approximately twenty locations W 1194, Composite/Whole Field Method The sample in each block consists of six or eight cores taken within a 60-foot radius from the sampling point. W 1194, Grid Method Sources UT Extension W 1194, Soil Testing for Commercial Farmers (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
TexasUnited StatesTexas only. Other states set their own rules.	Routine soil fertility samplingTexas A and M AgriLife Extension, Procedure for Taking Soil Samples	Wait At least 2 months after the last fertilization	One composite sample for every 10 to 40 acres (4.05 to 16.19 ha)	Separate samples for different soil types, land uses or fertilizer rates, cropping histories and terrain. Avoid fertilizer bands, small gullies, depressions, terraces, waterways and unusual areas.	0 to 6 inches (0 to 15.24 cm)	10 to 15 cores per composite (one core, then 9 to 14 more)	Official guidanceTexas A and M AgriLife Extension, Soil Sample Information Form (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension laboratory for Texas. Not law. In force from Under review Legal text Texas A and M AgriLife Extension Soil, Water and Forage Testing Laboratory, Soil Sample Information Form, Procedure for Taking Soil Samples The wording in the source Timing When sampling fertilized fields, avoid sampling directly in fertilized band and wait at least 2 months after last fertilization. step 3 Area per sample Take one composite sample for every 10 to 40 acres. Procedure for Taking Soil Samples, step 1 Method A separate sample should be taken for: step 1, followed by: areas with different soil types; different land uses or fertilizer application rates; different cropping histories; different terrain Areas with different soil types step 1(a) Areas with different land uses or fertilizer application rates step 1(b) Areas with different cropping histories (species and yields) step 1(c) Areas with different terrain step 1(d) Avoid sampling areas such as small gullies, slight field depressions, terrace, waterways, or unusual areas. step 2 When sampling fertilized fields, avoid sampling directly in fertilized band step 3 Depth Take a 0-6 inch sample, insure equal soil throughout this six inch depth. step 6 Cores It is important to repeat steps 4-6 an additional 9 to 14 times for each area identified in steps 1-3. step 7 Sources Texas A and M AgriLife Extension, Soil Sample Information Form (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
TexasUnited StatesTexas only. Other states set their own rules.	Soil monitoring on CAFO waste application fieldsTCEQ regulatory guidance for concentrated animal feeding operations	Season Before waste application begins, and after it begins Repeat GPS grid method: sampled annually on the same grid layout	Not specified	Composite per land management unit (LMU). Subsample locations by professional judgment, grid with random selection, or GPS grid.	0 to 6 inches (0 to 15.24 cm) and 6 to 24 inches (15.24 to 60.96 cm). Where 0 to 2 and 2 to 6 inch samples (0 to 5.08 and 5.08 to 15.24 cm) are required, take the 0 to 6 inch sample and divide it.	10 to 15 subsamples per depth per LMU, preferably 15	Official guidanceTCEQ RG-408, Soil Sampling for CAFOs (PDF)
Who it applies to, the exact wording and every source Who it applies to State agency guidance for CAFOs that apply animal waste to land. Not law: the requirements sit in 30 TAC Chapter 321, Subchapter B and the CAFO general permit. Laboratory and analysis An agronomic soil laboratory, using the test methods in the Texas A and M AgriLife Soil, Water and Forage Testing Laboratory procedures. Field identifiers GPS each subsample location and keep it for two years (grid and GPS grid methods). In force from Under review Legal text TCEQ RG-408, Soil Sampling for Concentrated Animal-Feeding Operations (CAFOs), revised December 2017 The wording in the source Timing Before you begin to apply waste, and after you begin applying waste in accordance with the CAFO rules and General Permit, you are required to collect and analyze representative soil samples from each permitted land management unit (LMU) RG-408 p. 1, What is the purpose of soil sampling? Sampling is conducted annually using the same grid layout to improve field sub-sampling consistency. RG-408 p. 3, GPS Grid Method Method Methods for locating subsamples include the following: professional judgment, grid and GPS Grid. RG-408 p. 2 Depth If you are required to take 0–2 in and 2–6 in samples, collect a 0–6 in sample and divide according to depth. RG-408 p. 2 If you cannot collect the entire 6–24 in sample for more than the minimum 10 subsamples, specify the average depth that was obtained for the LMU. RG-408 p. 3 Cores A representative composite sample typically should be composed of a composite of 10 to 15 (preferably 15) discrete subsamples for each depth increment within an LMU RG-408 p. 2 Laboratory and analysis Coordinate with an agronomic soil laboratory RG-408 p. 1 appropriate soil test methodology found in the Standard Operating Procedures (SOPs) for the Texas AgriLife Extension Service Soil, Water and Forage Testing Laboratory. RG-408 p. 2 Field identifiers GPS each subsample location and maintain the information for a period of two years. RG-408 p. 3, Grid Sampling and GPS Grid methods Sources TCEQ RG-408, Soil Sampling for CAFOs (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
UtahUnited StatesUtah only. Other states set their own rules.	Routine soil fertility samplingUSU Analytical Labs, Soil Sampling Procedure	Season Any time of year, early fall often preferred. Spring for the special nitrate test.	Not specified	Sample separately each area of uniform color, texture, drainage, and the same cropping and fertilizer treatment last year, from locations in a random pattern. Leave out non-typical spots or sample them separately.	Standard topsoil sample: surface to 12 inches (0 to 30.48 cm). For nitrate when applying manure, also 12 to 24 inches (30.48 to 60.96 cm) or 12 to 36 inches (30.48 to 91.44 cm).	8 to 10 locations per sample area	Official guidanceUSU Analytical Labs, Soil Analysis Information Sheet (PDF, Rev. 7/2023)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university laboratory for Utah. Not law. In force from Under review Legal text USU Analytical Labs, Soil Analysis Information Sheet, Soil Sampling Procedure (Rev. 7/2023) The wording in the source Timing WHEN: Any time of the year; early fall is often preferred. Soil Sampling Procedure, WHEN For special nitrate tests, sample in the spring Soil Sampling Procedure, WHEN Method Select an area having uniform color, texture, drainage, and the same cropping and fertilizer treatment last year. Soil Sampling Procedure, AREA Sample multiple locations within each similar area in a random pattern Soil Sampling Procedure, TAKING THE SAMPLE Leave out non-typical spots or sample them separately. Soil Sampling Procedure, AREA Depth Standard topsoil sample: from surface down to 12 inches Soil Sampling Procedure, DEPTH (a) Starting at the bottom of the hole in (b), sample the 12 to 24-inch (or 12 to 36-inch) depth. Special sampling for nitrate-N when applying manure, (c) Cores For each area to be sampled, take separate samples from 8 to 10 locations in a pattern that will represent the entire area. Soil Sampling Procedure, AREA Sources USU Analytical Labs, Soil Analysis Information Sheet (PDF, Rev. 7/2023) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
VermontUnited StatesVermont only. Other states set their own rules.	Soil sampling on fields that receive manure or fertilizerRequired Agricultural Practices (RAPs), Agricultural Nonpoint Source Pollution Control Program	Repeat At least once in every five years	Not specified	Not specified	Not specified	Not specified	ConditionalVermont Required Agricultural Practices Rule (effective November 23, 2018), PDF
Who it applies to, the exact wording and every source Who it applies to Farms that must follow the RAPs (Section 3.1) but are below the Certified Small Farm Operation threshold of Section 4.1: every field that receives mechanical application of manure, agricultural wastes or fertilizer. Outside the rule Certified Small Farm Operations (Section 4.1 sets the livestock numbers, and the more than 50 acres of annual cropland or vegetables with mechanically applied fertilizer, manure or agricultural wastes, that make a farm one) and permitted Medium and Large Farm Operations. They follow a field-by-field nutrient management plan to NRCS Code 590 or an approved equivalent under 6.03(a) instead. Laboratory and analysis Modified Morgan extractant, or other equivalent standards approved by the Secretary. Soil analysis records kept on the farm for five years. In force from 23 November 2018 Legal text Vermont Required Agricultural Practices Rule for the Agricultural Nonpoint Source Pollution Control Program, Section 6.03(c) The wording in the source Timing shall be soil sampled at least once in every five years Section 6.03(c) Who it applies to For all other farming operations subject to this rule, all fields receiving mechanical application of manure, agricultural wastes, or fertilizer shall be soil sampled Section 6.03(c) Compliance with the Required Agricultural Practices Rule is required if a person: Section 3.1 (followed by the thresholds (a) to (g)) Outside the rule All Certified Small Farm Operations as defined in Section 4 of this rule and all permitted Medium and Large Farm Operations managing manure, agricultural wastes, or fertilizer for use as nutrient sources shall implement a field-by-field … nutrient management plan consistent with the requirements of the USDA NRCS Nutrient Management Practice Code 590 or other equivalent standards approved by the Secretary. Section 6.03(a) (ellipsis marks footnote marker 20) (b) farms on a parcel or parcels of land greater than 50 acres used for the preparation, tilling, fertilization, planting, protection, irrigation, and harvesting of annual cropland where fertilizer, manure, or agricultural wastes are mechanically applied to said parcel or parcels; or Section 4.1(b) (4.1(a) sets the livestock numbers, 4.1(c) the same 50 acres for vegetable production) Laboratory and analysis using modified Morgan’s extractant or other equivalent standards approved by the Secretary. Section 6.03(c) Records of soil analysis, manure or other agricultural waste application, and fertilizer applications shall be maintained on the farm for a period five years and provided to the Secretary upon request. Section 6.03(c) In force (Effective November 23, 2018) Title page Sources Vermont Required Agricultural Practices Rule (effective November 23, 2018), PDF Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
VermontUnited StatesVermont only. Other states set their own rules.	Routine soil fertility samplingUVM Extension Agricultural and Environmental Testing Lab, How to Take a Soil Sample	Season Before lime, fertilizer or manure is added	Not specified	Zig-zag across an area as uniform as possible in soil type, cropping and fertilizing history, one you expect to fertilize as a unit.	Lawns, turf and other perennial sod: 4 to 6 inches (10.16 to 15.24 cm). Annually tilled crops: tillage depth, usually 6 to 10 inches (15.24 to 25.4 cm).	At least 15 to 20 for areas larger than a home garden or lawn of up to 10,000 square feet (10 cores minimum for those)	Official guidanceUVM Extension, How to Take a Soil Sample (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension laboratory for Vermont. Not law. In force from Under review Legal text University of Vermont Extension, How to Take a Soil Sample (3/2022) The wording in the source Timing Take samples before lime, fertilizer, or manure are added. How to Take a Soil Sample, opening Method The area to be sampled should be as uniform as possible in terms of soil type and cropping and fertilizing history. Where to sample For practical purposes it should be an area you expect to fertilize as a unit. Where to sample Collect a number of cores or slices by walking in a zig-zag pattern over the area. Take a good sample Depth Sampling depth should be 4 to 6 inches deep for lawns, turf, or other perennial sod, or tillage depth (usually 6 –10 inches) for annually tilled crops. Choose one of the following tools, soil probe or auger Cores Consider 10 cores as the minimum for home gardens and lawns up to 10,000 square feet in size. Take a good sample Larger areas should be represented by at least 15 to 20 samples. Take a good sample Sources UVM Extension, How to Take a Soil Sample (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
VirginiaUnited StatesVirginia only. Other states set their own rules.	Soil analysis behind a nutrient management planNutrient Management Training and Certification Regulations	Result valid Dated no more than 3 years before the plan begins Repeat The plan must recommend soil analysis for each field at least once every 3 years	A composite sample should represent up to about 20 acres (8.09 ha). Strip-cropped fields may be combined where soils, cropping history and fertility are similar.	Representative results by standard sampling and analysis methods (Methods of Soil Analysis, Part 3, 1996). Subfield grids or management zones may be used.	Fields not tilled in the past 3 years: 0 to 4 inches (0 to 10.16 cm). Fields tilled in the past 3 years: 0 to 6 inches (0 to 15.24 cm).	Not specified	Conditional4VAC50-85-140, Required nutrient management plan procedures
Who it applies to, the exact wording and every source Who it applies to Binds certified nutrient management planners, for the plans they write under Virginia’s voluntary certification program. It does not by itself require a farm to sample: a farm is covered only where it follows such a plan, and other laws, permits or contracts decide which farms must have one. Laboratory and analysis Mehlich I extraction for phosphorus, or other methods and laboratories approved by the department and correlated to Mehlich I. In force from 20 November 2014 Legal text 4VAC50-85, Nutrient Management Training and Certification Regulations, 4VAC50-85-140 A 2 f and D 4 The wording in the source Timing Soil analysis results shall be dated no more than three years prior to the beginning date of the nutrient management plan. 4VAC50-85-140 A 2 f Soil analysis shall be recommended for each field at least once every three years to determine the soil fertility and pH, and to update the nutrient management plan. 4VAC50-85-140 D 4 Area per sample A single composite soil sample should represent an area up to approximately 20 acres. 4VAC50-85-140 A 2 f Fields such as those common to strip cropping may be combined when soils, previous cropping history, and soil fertility are similar. 4VAC50-85-140 A 2 f Method Representative soil analysis results for fields shall be determined by using standard soil sampling and analysis methods according to Methods of Soil Analysis, Part 3, Chemical Methods, 1996 4VAC50-85-140 A 2 f Soil sampling of fields based on subfield grids or management zones may be utilized. 4VAC50-85-140 A 2 f Depth Representative soil sample cores shall be obtained from the soil surface to a depth of four inches (0-4") for fields that have not been tilled within the past three years 4VAC50-85-140 A 2 f and from the soil surface to a depth of six inches (0-6") for fields that are tilled or have been tilled within the past three years. 4VAC50-85-140 A 2 f Who it applies to This chapter governs the department’s voluntary Nutrient Management Training and Certification Program for individuals who prepare nutrient management plans. 4VAC50-85-20 A A certified nutrient management planner shall include, in each plan, nutrient application practices for each field in the plan. 4VAC50-85-140 A 1 Representative soil analysis results for fields shall be determined by using standard soil sampling and analysis methods 4VAC50-85-140 A 2 f Laboratory and analysis utilizing the Mehlich I extraction procedure for phosphorus or other methods and laboratories approved by the department and correlated to Mehlich I 4VAC50-85-140 A 2 f In force amended, Virginia Register Volume 31, Issue 3, eff. November 20, 2014. 4VAC50-85-140, Historical Notes (last amendment) Sources 4VAC50-85-140, Required nutrient management plan procedures Law 4VAC50-85-20, Purpose Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
VirginiaUnited StatesVirginia only. Other states set their own rules.	Soil monitoring on animal waste land application sitesVirginia Pollution Abatement (VPA) general permit for animal feeding operations and animal waste management	Repeat Once every 3 years (1/3 years)	Not specified	Composite samples. pH, phosphorus, potash, calcium and magnesium.	0 to 6 inches (0 to 15.24 cm), unless the approved nutrient management plan says otherwise	Not specified	Conditional9VAC25-192-70, Contents of the general permit
Who it applies to, the exact wording and every source Who it applies to Owners of animal feeding operations with 300 or more animal units using a liquid manure collection and storage system, and animal waste end-users (Part III), once the department accepts their registration for the VPA general permit. Applies on their land application sites. Laboratory and analysis Methods specified in the approved nutrient management plan. Monitoring data kept on site for five years. In force from Under review Legal text 9VAC25-192, VPA Regulation and General Permit for Animal Feeding Operations and Animal Waste Management, 9VAC25-192-70, Part I A 8 and A 9, Table 2 (Part III repeats them for animal waste end-users) The wording in the source Timing TABLE 2, SOILS MONITORING: Frequency 1/3 years; Sample Type Composite Part I, Table 2 (cells transcribed: pH row; the same for phosphorus, potash, calcium, magnesium) Method TABLE 2, SOILS MONITORING: Frequency 1/3 years; Sample Type Composite Part I, Table 2 (cells transcribed) Depth Soil monitoring shall be conducted at a depth of between 0-6 inches, unless otherwise specified in the approved nutrient management plan written for the animal feeding operation. Part I A 9 Who it applies to owners of animal feeding operations having 300 or more animal units utilizing a liquid manure collection and storage system 9VAC25-192-70, general permit cover page Any owner or animal waste end-user whose registration statement is accepted by the department will receive the following general permit and shall comply with the requirements of the general permit 9VAC25-192-70, opening paragraph Soil at the land application sites shall be monitored as specified in Table 2 of Part I. Part I A 8 Soil at the land application sites shall be monitored as specified in Table 2 of Part III. Part III A 8 (animal waste end-users) Laboratory and analysis Analysis of soil and waste shall be according to methods specified in the approved nutrient management plan written for the animal feeding operation. Part I A 11 All monitoring data collected as required by this section and any additional monitoring shall be maintained on site for a period of five years Part I A 12 Sources 9VAC25-192-70, Contents of the general permit Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
VirginiaUnited StatesVirginia only. Other states set their own rules.	Routine soil fertility samplingVirginia Cooperative Extension, Soil Sampling Instructions for the Farm	Season Fall sampling suggested, so lime can go on before the next season Wait At least 6 to 8 weeks after liming or fertilizing	Areas of 5 to 10 acres (2.02 to 4.05 ha) where fields vary. Precision grids typically 2.5 acres, 1 acre on small fields.	Zig-zag across each uniform area. Grid sampling, typically 2.5 acres, or smart sampling by topography, yield or soil map unit.	Cropland: plow depth, 6 to 8 inches or more (15.24 to 20.32 cm). Pasture and no-till crop fields: 2 to 4 inches (5.08 to 10.16 cm).	20 or more places per field, and at least 5 cores per acre represented. Grid points: 6 to 8 subsamples.	Official guidanceVirginia Cooperative Extension SPES-141NP (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for Virginia. Not law. In force from Under review Legal text Virginia Cooperative Extension SPES-141NP, Soil Sampling Instructions for the Farm (2019) The wording in the source Timing Sampling in the fall allows time to apply lime to adjust the soil pH before next year’s growing season SPES-141NP, step 2 For areas recently limed or fertilized, delay sampling at least six to eight weeks. SPES-141NP, step 2 Area per sample the slope, drainage, or soil type will make it desirable to divide the field into small areas of 5 to 10 acres each. SPES-141NP, step 3 To begin, fields are first divided into grids, with typical grid size being 2.5 acres. SPES-141NP, Soil sampling for precision farming For small fields, a one acre grid size will give a more precise representation of the fertility across the field SPES-141NP, Soil sampling for precision farming Method Zig-zag across the field or area as shown in the diagram. SPES-141NP, step 4 “Smart sampling” consists of sampling those areas of the field that are obviously different, such as with respect to topography (hilltops, low areas), or if a combine yield monitor has been used, high-yielding and low-yielding areas in the field. SPES-141NP, precision farming If the field has been mapped, it can be divided by soil series (i.e., soil mapping unit). SPES-141NP, precision farming Depth The desired depth for cropland is plow depth (6 to 8 inches or more), and 2 to 4 inches for pasture land, or no-till crop fields. SPES-141NP, step 5 Cores Take the sample from 20 or more places in the field. SPES-141NP, step 4 Samples should be made up of at least 5 subsamples or cores from each acre represented by the sample. SPES-141NP, step 4 with 6-8 subsamples being taken in a 10′ circle around the ATV SPES-141NP, precision farming Sources Virginia Cooperative Extension SPES-141NP (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
WashingtonUnited StatesWashington only. Other states set their own rules.	Dairy soil analysis records: yearly postharvest nitrate and a soil analysis every three yearsDairy Nutrient Management Act, recordkeeping	Repeat Postharvest soil nitrate nitrogen analysis every year Repeat A current soil analysis every three years (contents under Laboratory)	Not specified	Not specified	Not specified	Not specified	ConditionalWAC 16-611-020, Washington State Legislature
Who it applies to, the exact wording and every source Who it applies to Dairy producers, who must keep records showing that nutrients applied to crop land were within acceptable agronomic rates. Laboratory and analysis Three-year analysis: organic matter, pH, ammonium nitrogen, phosphorus (Bray-1 below pH 7, Olsen bicarbonate at pH 7 or above), potassium and electrical conductivity. In force from 29 November 2012 Legal text WAC 16-611-020, Recordkeeping requirements (dairy nutrient management), WAC 16-611-020(2)(a) The wording in the source Timing (i) Annual postharvest soil nitrate nitrogen analysis; WAC 16-611-020(2)(a)(i) (ii) Every three years, a current soil analysis that includes: WAC 16-611-020(2)(a)(ii) Who it applies to (1) In accordance with RCW 90.64.010 (17)(c) and 90.64.102, dairy producers must maintain records to demonstrate that applications of nutrients to crop land are within acceptable agronomic rates. WAC 16-611-020(1) Laboratory and analysis (A) Organic matter; (B) pH; (C) Ammonium nitrogen; (D) Phosphorus (the Bray-1 method must be used to determine soil phosphorus for soils below pH 7 and the Olsen bicarbonate method must be used for soils at or above pH 7); WAC 16-611-020(2)(a)(ii)(A) to (D) (E) Potassium; and (F) A measure of electrical conductivity. WAC 16-611-020(2)(a)(ii)(E) and (F) In force WSR 12-22-019, § 16-611-020, filed 10/29/12, effective 11/29/12. History note Sources WAC 16-611-020, Washington State Legislature Law Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
WashingtonUnited StatesWashington only. Other states set their own rules.	Soil sampling for dryland winter wheat nutrient managementWSU Extension, Eastern Washington Nutrient Management Guide (dryland winter wheat)	Not specified	Not specified	A field composite, or 2 to 3 management units by slope, aspect and drainage, each sampled separately.	Winter wheat nitrogen: one-foot increments to at least 4 feet (121.92 cm) or a restrictive layer. Phosphorus: the surface foot, 0 to 12 inches (0 to 30.48 cm).	Not specified	Official guidanceWSU Extension EB1987E (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for eastern Washington dryland winter wheat. Not law. In force from Under review Legal text WSU Extension EB1987E, Eastern Washington Nutrient Management Guide (published March 2005, revised July 2013) The wording in the source Method If a field will be fertilized as one unit, collect cores from several representative locations throughout the field and combine these together for the sample. EB1987E, Box C A typical field in eastern Washington may be divided into 2 to 3 management units based on slope, aspect, and drainage. EB1987E, Box C Depth For winter wheat, samples should be collected in one-foot increments to a minimum depth of four feet or a restrictive layer. EB1987E, B1 Phosphorus recommendations are based on soil test values in a surface one-foot sample (Table 1). EB1987E, Phosphorus (P) recommendations Sources WSU Extension EB1987E (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
WisconsinUnited StatesWisconsin only. Other states set their own rules.	Routine soil fertility samplingUW Extension A2100, Sampling Soils for Testing	Repeat At least every 4 years. Sands and loamy sands every 2 years. Season Any convenient time; fall may be best, so lime and fertilizer advice arrives in time. Hayfields after any cutting. Stay consistent from one year to the next.	One composite per 5 acres (2.02 ha) on responsive fields and fields not sampled in the past 4 years. Fewer samples on nonresponsive fields tested within 4 years (Table 1).	W-shaped pattern for a whole field composite. Unaligned grid-point sampling at 200 feet (about 1 acre) or, on nonresponsive fields, 300 feet (2 to 2.5 acres). Zone (smart) sampling.	Plow depth or at least 6 inches (15.24 cm). Chisel or disk: three quarters of tillage depth. Ridge till: 6 inches on ridges, 4 in furrows. No-till: 6 to 7 inches (17.78 cm) for fertilizer advice, plus 2 inches for pH if an acid layer is suspected.	At least 10 cores per composite. 10 to 20 cores give a more representative sample.	Official guidanceUW Extension A2100, Sampling Soils for Testing (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for Wisconsin. Not law in itself; plans prepared to the NRCS 590 standard follow its sampling techniques. Laboratory and analysis A Wisconsin certified laboratory, for plans that must follow the NRCS 590 standard. In force from Under review Legal text University of Wisconsin-Extension A2100, Sampling Soils for Testing (Peters and Laboski, 2013) The wording in the source Timing Most fields should be retested at least every 4 years to monitor soil fertility levels of immobile nutrients and pH A2100 p. 4, How often to sample Exceptions include sands and loamy sands, which should be tested every 2 years. A2100 p. 4, How often to sample Take soil samples at any convenient time. A2100 p. 3, When to take soil samples To receive your recommendations early enough to enable you to apply the lime and fertilizer needed, it may be best to sample in the fall. A2100 p. 3, When to take soil samples Hayfields can be sampled after any cutting. Regardless of when you sample, it is best to be consistent from one year to the next. A2100 p. 3 Area per sample For responsive fields, as well as all fields that have not been sampled in the past 4 years, take one composite sample for every 5 acres. A2100 p. 3, step 3 Table 1. Recommended sample intensity for uniform fields: fields tested more than 4 years ago OR fields testing in the responsive range, all fields, 1 sample/5 acres; nonresponsive fields tested within past 4 years, 5–10 acres 2, 11–25 acres 3, 26–40 acres 4, 41–60 acres 5, 61–80 acres 6, 81–100 acres 7 A2100 p. 1, Table 1 (transcribed) Method use a W-shaped sampling pattern (as shown in Figure 1) over the whole area the sample represents. A2100 p. 1 Where there is no information about the P or K status of the field or where previous tests were in the responsive range, a 200-foot grid size should be used. This is equivalent to approximately one soil sample per acre. A2100 p. 2, site-specific management Fields that have soil test P and K levels in the nonresponsive categories should be grid-point sampled on a 300-foot grid. This is equivalent to one soil sample for every 2 to 2.5 acres. A2100 p. 2 Smart (zone or directed) sampling. Another approach gaining support among researchers is smart sampling, also known as directed or management zone sampling. A2100 p. 3 Depth Insert the probe or auger into the soil to plow depth or at least 6 inches. A2100 p. 3, step 2 Chisel plowing and offset disking. Take soil samples to ¾ of the tillage depth. A2100 p. 4, Tillage system considerations Sample ridges to a 6-inch depth and furrows (between rows) to a depth of 4 inches. A2100 p. 4, Till-plant and ridge tillage For fertilizer recommendations, take a separate sample to a depth of 6 to 7 inches. A2100 p. 4, No-till If an acid layer is suspected, take a separate sample to a depth of only 2 inches. A2100 p. 4, No-till Cores Each sample should be made up of a minimum of 10 cores to ensure accurate representation of the nutrient needs of the field. A2100 p. 1 Research has shown that taking 10 to 20 cores provides a more representative sample of the area than when samples are made up of fewer cores. A2100 p. 1 Laboratory and analysis These provisions currently include: following the soil sampling techniques outlined above, soil testing by a Wisconsin certified laboratory A2100 p. 3, How to take soil samples (590 standard) Sources UW Extension A2100, Sampling Soils for Testing (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.
WyomingUnited StatesWyoming only. Other states set their own rules.	Pre-plant soil sampling for dry beans onlyUniversity of Wyoming Extension, Nutrient Management Guidelines for Dry Beans	Season Before planting. Sample at the same time of year each time.	Typical approach: one composite from a 20 to 40 acre field (8.09 to 16.19 ha)	Not specified	Tillage zone, usually 6 or 8 inches (15.24 or 20.32 cm), for pH, organic matter, N, P, K and micronutrients. For nitrate, a 12 inch (30.48 cm) core split into 0 to 6 and 6 to 12 inches, unless tillage mixes the soil to one foot.	15 to 20 random locations	Official guidanceUniversity of Wyoming Extension B-1016R (PDF)
Who it applies to, the exact wording and every source Who it applies to Advice from the public land-grant university extension service for Wyoming, written for dry bean fields only (its fertilizer tables are for irrigated dry beans). Not other crops. Not law. In force from Under review Legal text University of Wyoming Cooperative Extension Service B-1016R, Nutrient Management Guidelines for Dry Beans (June 2005) The wording in the source Timing Before planting occurs, a representative soil sample should be collected from the tillage zone (usually a 6 or 8 inch depth) B-1016R p. 1 For best results, always collect samples at the same time of the year. B-1016R, Potassium Area per sample A typical sampling approach is to extract a 12-inch soil core from 15 to 20 random locations within a 20- to 40-acre field. B-1016R p. 1 Depth Before planting occurs, a representative soil sample should be collected from the tillage zone (usually a 6 or 8 inch depth) for determination of pH, organic matter, available nitrogen, phosphorus, potassium, and micro- B-1016R p. 1 Nitrogen recommendations are more reliable when based on available nitrogen (nitrate-N) to a depth of 12 inches. B-1016R p. 1 Divide each core into two 6-inch sections, placing all top sections into one container and all bottom sections into another B-1016R p. 1 If tillage operations thoroughly mix soil to a depth of one foot, it is not necessary to separate the surface and subsurface layers. B-1016R p. 1 Cores A typical sampling approach is to extract a 12-inch soil core from 15 to 20 random locations within a 20- to 40-acre field. B-1016R p. 1 Sources University of Wyoming Extension B-1016R (PDF) Guidance Sources re-checked every two months, last update October 2026. Reviewed by GeoPard editorial team.

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