Sustainable Agriculture

A program of the National Center for Appropriate Technology • 1-800-346-9140 • www.attra.ncat.org

Tipsheet: Assessing the Soil 

Resource for Beginning

Organic Farmers

Why Do Soil Assessment?

It is important for farmers, especially organic farmers, to understand how to assess their soils in order 

to better manage them. Assessing your soils through 

both field and lab observations can identify limitations in your soil and help guide soil-management 

decisions. Organic production practices depend 

heavily on good soil management to support plant 

health, as well as to support the health of the agricultural ecosystem. An important component of good 

soil management in an organic system is understanding how to manage nutrients. This tipsheet will 

touch on all these facets and provide resources for 

further education on this complex topic, but four 

general rules should be kept in mind:

y Keep the soil covered as much as possible 

(mulch, cover crops, or crops)

y Keep soil disturbance to a minimum—either chemical (fertilizers and pesticides) or physical (tillage)

y Provide regular additions of organic matter (compost, cover crops, crop residues, manure)

y Regular soil testing and observation (plant and root health, drainage problems, etc.)

Rules Relating to Soil Standard

The USDA organic regulations and 7 CFR §205.203, Soil Fertility and Crop Nutrient Management Practice Standard, 

do not define specific land practices that producers must use. But the standard does identify general soil management and environmental protection objectives. From these objectives, producers and the organic certifiers they 

work with must determine whether specific farming practices meet the National Organic Program (NOP) criteria.

§205.203(a): Select and implement tillage and cultivation practices that maintain or improve the physical, chemical, and biological condition of soil and minimize soil erosion.

§205.203(b): Manage crop nutrients and soil fertility through rotations, cover crops, and the application of plant 

and animal materials.

§205.203(c) and (d): Manage plant and animal materials to maintain or improve soil organic matter content in a 

manner that does not contribute to contamination of crops, soil, or water by plant nutrients, pathogenic organisms, heavy metals, or residues of prohibited substances. 

§205.601(j)(6)(i): Micronutrients—not to be used as a defoliant, herbicide, or desiccant. Those made from nitrates 

or chlorides are not allowed. Soil deficiency must be documented by testing. 

Photo: Rex Dufour, NCAT
Page 2 Tipsheet: Assessing the Soil Resource for Beginning (Organic) Farmers

*Farmers’ observations are an important component of soil assessment. There are additional tools, such as soil maps 

and soil testing, which can help farmers understand how to improve their soils’ function. Most of the criteria of a 

good soil listed below can be observed by the farmer: 

y feels soft and crumbles easily

y drains well and warms up quickly in the spring

y does not crust after planting

y soaks up heavy rains with little runoff

y stores moisture for drought periods

y has few clods and no hardpan

y resists erosion and nutrient loss

y supports high populations of soil organisms

y has a rich, earthy smell

y does not require increasing inputs for high yields

y produces healthy, high-quality crops

Soil is made up of different sizes of minerals—sand, silt and clay—as 

well as organic matter and spaces for water and air. The function of soil 

high in either sand or clay content can be improved with additions of organic matter.

Sandy soil: Drains well, but doesn’t store water or nutrients well. May have nematode problems.

Silty soil: Generally considered to be quite fertile, and drains more readily than clay due to larger-size particles.

Clay soil: Generally higher in nutrients and ability to store water, but drains slowly, and will be prone to compaction if 

worked when too wet. 

Basic Steps to Assess Your Soil

Assessment Step Assessment Activity

Establish baseline 

information

Research the history of crops/fertilizers/pesticides used on the soil and other soil management practices (heavy machinery, ripping, etc.).

Get soil map for farm location that shows soil types (WebSoilSurvey).

Using soil map, take samples of the soils for analysis.

Soil observation*

Look for ponding, crusting, places where plants are consistently unthrifty, and other signs the soil is 

not functioning. Test for compaction layer where ponding occurs. Spend time in the field during prolonged dry or wet weather to observe the soil and plant health.

Develop soil management plan

Use your soil tests as a guide to develop a plan to manage your soils. Most soils are low in organic matter and various other nutrients. A soil test documenting deficiency of micronutrients is required by the 

NOP in order to apply micronutrients. 

Soil management

Good soil management is as much an art as it is a science. Understanding what your soil needs is a first 

step and will help in deciding which combinations of compost, crop rotations, cover crops, manure, 

mulches, tillage, proper fertilizers & rates to use to bring your soil to optimum function. Don’t expect 

instant results

Soil monitoring

Observations of plant health and other attributes of the soil outlined below will tell the grower if soil 

function is improving or not. Soil tests done every year, or at least every other year, will help indicate 

trends in soil quality. Annual inspections by your organic certifier will help highlight any concerns 

related to soil or nutrient management. 

Special case: urban 

soils

Urban soils should always be tested for heavy metal contamination before any planting is done, and 

they should be tested for the nutrient status of the soil. Samples for heavy metal testing should be 

taken close to buildings and along streets or sidewalks—these are the likely “hotspots” for lead contamination from paint or leaded gasoline. See ATTRA’s Start a Farm in the City pages 9-13 for more 

information about testing and mitigation https://attra.ncat.org/attra-pub/summaries/summary.

php?pub=21

 Figure 1. Relative size comparison between sand, 

silt, and clay of the fine earth fraction. Source: www.

nature.com
www.attra.ncat.org Page 3

Soil Health Indicators

Indicator Best Assessed Poor Medium Good

Earthworms Spring/fall good soil 

moisture

0-1 worms in shovelful 

of top foot of soil. No 

casts or holes.

2-10 in shovelful.

Few casts, holes, or

worms.

10+ in top foot of soil. 

Lots of casts and holes 

in tilled clods. Birds 

behind tillage.

Organic Matter 

Color Moist soil Topsoil color similar to subsoil color.

Surface color closer

to subsoil color.

Topsoil clearly defined,

darker than subsoil.

Organic Matter 

Residues Anytime No visible residues Some residues Noticeable residues

Root Health Late spring (rapid 

growth stage)

Few, thick roots. No 

subsoil penetration. Off 

color (staining) inside 

root.

Roots well branched. A 

few roots grow through 

cracks and reach into 

subsoil. 

Roots fully branched 

and extended, reaching into subsoil. Root 

exterior and interior are 

white.

Subsurface

Compaction

Best pre-tillage or 

postharvest. Good soil 

moisture.

Wire breaks or bends 

when inserting flag. 

Have to push hard, 

need fist to push flag 

in.

Flag goes in easily with 

fingers to twice the 

depth of plow layer.

Soil Tilth

Mellowness

Friability

Good soil moisture.

Looks dead. Like brick or 

concrete, cloddy. Either 

blows apart or is hard to 

pull drill through.

Somewhat cloddy, 

balls up, requires multiple secondary tillage 

passes for good seedbed.

Soil crumbles well, can 

slice through, like cutting butter. Spongy 

when you walk on it.

Erosion After heavy rainfall.

Large gullies over 2 

inches deep joined to 

others, thin or no topsoil, rapid runoff the 

color of soil.

Few rills or gullies, 

gullies up to 2 inches 

deep. Some swift runoff, colored water. 

No gullies or rills, clear 

or no runoff. 

Water-Holding

Capacity

After rainfall.

During growing season.

Plant stress two days 

after a good rain.

Water runs out after a 

week or so.

Holds water for a long 

period of time without 

puddling.

Drainage,

Infiltration After rainfall.

Water sits for a long 

time, evaporates more 

than drains, always very 

wet ground.

Water sits for short 

period of time, eventually drains.

No ponding, no runoff, 

water moves through 

soil steadily. Soil not 

too wet, not too dry.

Crop Condition

(how well it grows)

Growing season.

Good soil moisture.

Problem growing 

throughout season, 

poor growth, yellow or 

purple color.

Fair growth, spots in 

field different, medium 

green color.

Normal healthy dark 

green color, excellent growth all season, 

across field.

pH Anytime, but at same 

time of year each time.

Hard to correct for 

desired crop. Easily correctable. Proper pH for crop.

Nutrient-Holding

Capacity

Over a five-year period, 

always at same time of 

year.

Soil tests dropping with 

more fertilizer applied 

than crops used.

Little change or slow

downward trend.

Soil tests trending up 

in relation to fertilizer 

applied and crop harvested.
Page 4 Tipsheet: Assessing the Soil Resource for Beginning (Organic) Farmers

Produced by the National Center for Appropriate Technology

www.ncat.org • 1-800-275-6228 (1-800-ASK-NCAT)

(Parent organization to the ATTRA Project, www.attra.ncat.org)

Tipsheet: Assessing the Soil Resource for Beginning 

Organic Farmers

By Rex Dufour, NCAT Agriculture Specialist

Published July 2015

Taking Soil Samples y Tools should be either stainless steel or chrome-plated to avoid 

contamination of the sample. 

y Preferably, collect in a clean, dry plastic container as soil may 

pick up zinc, for example, if the container is galvanized. 

y The greater number of soil samples taken from a location, the 

greater the probability that the soil test results will accurately 

reflect the field condition.

y A soil map can be of help in distinguishing areas to sample. 

Each soil type’s samples should be a combination of five to 20 

subsamples. Send about 2 cups of the composite sample to the laboratory.

y Sample from areas of main root development, usually the top six to 12”. 

y Before collecting each subsample, scrape away surface residue, then sample.

Resources

Building Soils for Better Crops. 2010. Fred Magdoff, Harold van Es. 294 p.

www.sare.org/Learning-Center/Books/Building-Soils-for-Better-Crops-3rd-Edition

This is a free PDF download with a good overview of soils, the role of organic matter in healthy soils, and ecological soil 

management, all illustrated with good graphics.

Managing Cover Crops Profitably 3rd Edition. 

www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition

This book explores how and why cover crops work and provides all the information needed to build cover crops into any 

farming operation. 

NRCS Soil Quality Indicator Sheets. 

www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/health/assessment/?cid=stelprdb1237387

Has short guidelines about assessingthe following: aggregate stability, available water capacity, bulk density, infiltration, 

slaking, soil crusts, soil structure and macropores, reactive carbon, soil electrical conductivity, soil nitrate, soil pH, earthworms, particulate organic matter, and others.

Nutrient Management Plan (590) for Organic Systems. 2013. 30 p.

https://attra.ncat.org/attra-pub/summaries/summary.php?pub=465

This document is an instruction guide for creating and implementing a nutrient management plan (NMP) on certified or 

transitioning organic lands.

Soil Management: National Organic Program Regulations. 2005. Barbara Bellows. 20 p.

https://attra.ncat.org/attra-pub/summaries/summary.php?pub=180

This publication provides management guidelines for meeting, and measurable parameters for monitoring, NOP objectives related to soil management.

WebSoilSurvey: http://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx

Can provide soil map and soil descriptions if you have the address of the farm.

USDA Organic Regulations 7 CFR 205: www.ams.usda.gov/nop

Cornell Soil Health website: http://soilhealth.cals.cornell.edu

This site provides a free download of the Cornell Soil Health Manual, among other resources.

Crop Rotations on Organic Farms: A Planning Manual. 2009. C.L. Mohler & S.E. Johnson, editors. 156 p. 

www.sare.org/Learning-Center/Books/Crop-Rotation-on-Organic-Farms

www.al-labs-west.com/extra-pages.php?section=Soil%20

Analysis

This product was developed with support from 

U.S. Department of Agriculture’s Agricultural Marketing Service, National Organic Program