Soil Testing and Fertility Planning

Why test soil at all?

Plants take nutrients from the soil, and what is there varies a great deal from farm to farm and even field to field. Adding fertilizer or lime without testing can waste money and can create problems, such as excess nutrients that run off into water or a pH that hurts the crop.

A test gives you a baseline. Repeating it every few years shows you whether your management is building or draining fertility.

How do I take a good sample?

A useful sample represents the area, not one lucky spot. Walk the field or bed, collect several small cores from different places, mix them in a clean bucket, and send a portion to the lab. Keep separate samples for areas that differ, such as the garden and a hayfield, or a wet corner and a dry slope.

Use clean tools and avoid contaminating the sample with fertilizer, ash, or manure. Your lab or extension office will give specific instructions on depth and handling, and I recommend following theirs over general advice.

• Sample each distinct area separately
• Collect from many spots and mix
• Use clean tools and containers
• Follow your lab's instructions for depth and drying

Where do I send it?

Many state universities and extension offices offer soil testing, and there are private labs too. Ask your county extension office which lab they trust for your region, because methods and recommendations differ by area. Costs vary by lab, so check current pricing with them directly.

Choose a lab whose recommendations are written for your region and crops, and use the same lab each time so results are comparable over the years.

If you plan to sell produce, ask your state agriculture department whether any testing is required for the way you sell.

How do I read the report?

A typical report lists soil pH, organic matter, and levels of major and minor nutrients, along with recommendations. Soil pH matters because it affects how available nutrients are to plants. Organic matter reflects soil health and water-holding ability.

Do not be intimidated by the numbers. The report usually states whether each nutrient is low, adequate, or high, and suggests amounts for the crop you named. If something confuses you, call the lab or your extension agent and ask them to walk through it.

How do I plan fertility after the test?

Match inputs to the report and to the crop. Compost, manure, cover crops, and purchased fertilizers each supply nutrients differently and at different speeds. Be aware that some sources add more of one nutrient than the crop needs, so check the numbers rather than assuming.

If you use manure, ask your extension office about timing and handling to protect water and food safety, since rules and guidance vary by state and crop. Keep records of what you apply so you can compare it to future tests.

• Use test results, not habit, to decide inputs
• Count nutrients from compost and manure
• Ask about timing to protect nearby water
• Record each application

How often should I retest?

Many growers retest every few years, and more often if they are trying to fix a problem or adjust pH. Test in the same season each time so results are comparable. Keep every report in one folder or spreadsheet and watch the trends.

If crops struggle even when the test looks fine, look at drainage, compaction, pests, and weather before adding more fertilizer.

Share what you learn with neighbors who farm similar ground. Comparing reports and results across nearby farms helps everyone judge what is normal for your area and what needs attention.

What can soil testing not tell me?

A standard test does not diagnose every problem. It will not tell you about compaction, drainage, disease organisms, or most contaminants. If you suspect lead, old pesticide residues, or other contamination, ask your county health department or extension office what testing is appropriate before you grow food in that ground.

Soil tests also reflect one moment. Weather, recent amendments, and where the sample was taken all affect the result. Treat the report as a well informed starting point, then watch how your crops respond and adjust.

Pair the test with your own eyes. Look at plant color and vigor, root growth, how water drains after rain, and whether the soil crumbles or cakes. The numbers and the field should tell a consistent story.

• Ask about contamination testing for old farm or building sites
• Remember a test is a snapshot
• Combine lab data with field observation

Last reviewed: November 12, 2026. Written by the Rural Farm Life Editorial Team. See our editorial policy.