Soil testing for farm and ranch land

A soil map, a walk across the field and a lab test each answer different questions. Here is how they differ, how to prepare, and where to find a lab.

Find soil testing help

Choose the state where the land is to see public soil testing labs that serve it, their listed tests, sampling instructions and fee pages, and the Extension office that can help interpret results.

Three kinds of soil information

  • Mapped soil survey information. The NRCS Web Soil Survey shows mapped soil units, their typical properties and limitations. It is drawn at a scale where one map unit can include different soils, so it may not represent every part of a property, and a point lookup is not a summary of a whole farm.
  • Field observations. Walking the land, digging test holes, and noting wet spots, slope, rock and erosion tell you about this site, but not its nutrient levels.
  • A current laboratory test. A sample from your field, taken the way the lab instructs, is the only one of the three that measures current fertility. Mapped pH or old test results are not a fresh nutrient test for your field.

Different tests answer different questions

A routine fertility test (pH, phosphorus, potassium and similar) guides lime and fertilizer decisions. It does not certify that soil is free of contamination, that produce is safe, that a site will pass a septic or percolation test, or that it can support a foundation. Contamination and heavy-metal screening, irrigation and drinking-water testing, and geotechnical or percolation work are separate services, often from different providers and local offices.

Before you sample

  1. Decide what you plan to grow or graze, since labs and recommendations depend on the crop.
  2. Map distinct field areas (different soils, slopes, past use or management) and sample them separately.
  3. Follow the chosen lab's own sampling instructions: depth, number of cores and tools vary by lab and crop.
  4. Send the sample information and field history the lab asks for.
  5. Review the results with your county Extension office or a qualified crop adviser before buying inputs.

Farms and Ranches does not accept uploaded lab reports and does not produce fertilizer or pesticide recommendations.

Our full soil testing guide is in editorial and specialist review and will appear here once reviewed.