Soil sampling requirements in Indiana

Q: When in the year should soil be sampled in Indiana?

Purdue Extension soil sampling guidelines (official guidance): When no crop is standing: spring before planting or fall after harvest, before fertilizer or lime. Keep the same season each time.

Q: How deep should soil samples be taken in Indiana?

Purdue Extension soil sampling guidelines (official guidance): Conventional tillage: 0 to 8 inches. Conservation tillage: separate 0 to 4 inch sample for pH and lime, 0 to 8 inches for fertility.

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

Under IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan: A uniform 100-acre field needs at least 5 composite samples of no more than 20 acres each, and at least 60 cores in all, 12 per sample.

State guidance: IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan and Purdue Extension soil sampling guidelines.

Soil sampling in Indiana: frequency, area, depth and cores

How often do you need to soil sample in Indiana?

IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan Official guidance 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.
Purdue Extension soil sampling guidelines Official guidance Once every four years in most soils. Every two years on sandy or highly managed soils (irrigated, silage or hay fields).

When in the year should soil be sampled in Indiana?

Purdue Extension soil sampling guidelines Official guidance When no crop is standing: spring before planting or fall after harvest, before fertilizer or lime. Keep the same season each time.

How many acres can one soil sample cover in Indiana?

IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan Official guidance IDEM: each soil test may represent no more than 20 acres (8.0937 ha).
Purdue Extension soil sampling guidelines Official guidance 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.

How deep should soil samples be taken in Indiana?

Purdue Extension soil sampling guidelines Official guidance Conventional tillage: 0 to 8 inches. Conservation tillage: separate 0 to 4 inch sample for pH and lime, 0 to 8 inches for fertility.

How many cores go into one soil sample in Indiana?

IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan Official guidance IDEM: 12 to 15 plugs recommended for a composite from a 20 acre area.
Purdue Extension soil sampling guidelines Official guidance 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.

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

IDEM guidance on the Confined Feeding Operation (CFO) rule, 327 IAC 19, manure management plan: A uniform 100-acre field needs at least 5 composite samples of no more than 20 acres each, and at least 60 cores in all, 12 per sample.

Samples and cores for any field size

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

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 Indiana

Soil sampling requirements in Indiana

Soil sampling in Indiana: frequency, area, depth and cores

How often do you need to soil sample in Indiana?

When in the year should soil be sampled in Indiana?

How many acres can one soil sample cover in Indiana?

How deep should soil samples be taken in Indiana?

How many cores go into one soil sample in Indiana?

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

The wording in the source

Timing

Area per sample

Method

Cores

Who it applies to

Laboratory and analysis

Sources

The wording in the source

Timing

Area per sample

Method

Depth

Cores

Laboratory and analysis

Field identifiers

Sources

Plan the points to the rule that applies

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