Soil sampling requirements in New Mexico

Q: How many acres can one soil sample cover in New Mexico?

NMSU Cooperative Extension sampling advice (official guidance): Divide crop fields larger than 25 acres (10.12 ha) into separate sampling sections.

Q: How many soil samples does a 100-acre field need in New Mexico?

Under NMSU Cooperative Extension sampling advice: A uniform 100-acre field needs at least 4 composite samples of no more than 25 acres each, and at least 40 cores in all, 10 per sample.

State rules: 20.6.6 NMAC, Ground Water Protection: Supplemental Permitting Requirements for Dairy Facilities. State guidance: NMSU Cooperative Extension sampling advice.

Soil sampling in New Mexico: frequency, area, depth and cores

How often do you need to soil sample in New Mexico?

Ground water protection, supplemental permitting requirements for dairy facilities (Dairy Rule) Conditional Annually on every field that has received wastewater or stormwater, cropped or fallow.
NMSU Cooperative Extension sampling advice Official guidance Every year before the crop season; at least every other year.

When in the year should soil be sampled in New Mexico?

Ground water protection, supplemental permitting requirements for dairy facilities (Dairy Rule) Conditional Before the first wastewater application on a new field; an initial event on every field in the first year of each permit term.

How many acres can one soil sample cover in New Mexico?

NMSU Cooperative Extension sampling advice Official guidance Divide crop fields larger than 25 acres (10.12 ha) into separate sampling sections.

How deep should soil samples be taken in New Mexico?

Ground water protection, supplemental permitting requirements for dairy facilities (Dairy Rule) Conditional 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).
NMSU Cooperative Extension sampling advice Official guidance Untilled ground (direct-seeded fields, orchards, vineyards): 6 to 8 inches (15.24 to 20.32 cm). Tilled fields: 12 inches (30.48 cm).

How many cores go into one soil sample in New Mexico?

Ground water protection, supplemental permitting requirements for dairy facilities (Dairy Rule) Conditional 15 cores per composite.
NMSU Cooperative Extension sampling advice Official guidance 10 to 15 subsamples from the same depth per sample.

How many soil samples does a 100-acre field need in New Mexico?

NMSU Cooperative Extension sampling advice: A uniform 100-acre field needs at least 4 composite samples of no more than 25 acres each, and at least 40 cores in all, 10 per sample.

Samples and cores for any field size

Soil sampling rules in New Mexico, with the exact wording of each source
Country / region	Purpose / programme	Time / frequency	Area per sample	Method	Depth	Cores	Status and source
United States
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.

United States: federal rules and every other state

Soil sampling regulations in every country

Report an outdated requirement: info@geopard.tech

Plan the points to the rule that applies

Set the area per sample, the cores and the depth your rule asks for. GeoPard places the points on a grid or by zone, routes the walk, prints the labels and takes the plan to the field on a phone.

Create a sampling plan See the Soil Sampling Planner

A planning reference built from official sources, not legal advice. Rules apply by jurisdiction, nutrient, land use and programme: check the current official text and your laboratory’s instructions before fieldwork.

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Soil sampling requirements in New Mexico

Soil sampling requirements in New Mexico

Soil sampling in New Mexico: frequency, area, depth and cores

How often do you need to soil sample in New Mexico?

When in the year should soil be sampled in New Mexico?

How many acres can one soil sample cover in New Mexico?

How deep should soil samples be taken in New Mexico?

How many cores go into one soil sample in New Mexico?

How many soil samples does a 100-acre field need in New Mexico?

The wording in the source

Timing

Method

Depth

Cores

Who it applies to

Laboratory and analysis

Field identifiers

In force

Sources

The wording in the source

Timing

Area per sample

Method

Depth

Cores

Laboratory and analysis

Sources

Plan the points to the rule that applies

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