Soil Tests

A farm can obtain a Web Soil Survey (WSS) that provides soil data and information produced by the National Cooperative Soil Survey. It is operated by the USDA Natural Resources Conservation Service (NRCS) and provides access to the largest natural resource information system in the world. Soil survey's can be used for general farm, local, and wider area planning. An excellent publication on understanding fertilization recommendations based on soil samples is A General Guide for Crop Nutrient and Limestone Recommendations in Iowa

Soil sampling
Diagram of sampling soils

Phosphorus (P), Potassium (K) and Lime

  • Needs and rate are determined by a soil test!
  • Collect multiple sub-samples with a soil sample corer, or other means.
  • Avoid non-representative areas around trees, water tanks, hay feeding areas, etc.
  • Sample collection depth is important!
  • Sample 6" for phosphorus (P) & potassium & (K) evaluations.
  • Sample 2 to 3” for lime evaluation. 
  • Sample at tillage depth for new seeding or re-seeding evaluations.

The tool to sample soil can usually be obtained from a local extension office.

Soil Testing: A Must for Proper Pasture Management

Sampling soil
Taking a soil sample
Sampling soil tool
Depth for taking a soil sample

Why is Lime recommended? 

  • The soil 'acidity' (pH) influences the availability of fertilizer nutrients and soil microbial activity.
  • Lime is used to raise a low soil pH (neutralize an acid condition). Only add lime if a soil test says that you need it!
pH for Forage Crops
Crop pH for Forage Crops


Target pH

Don't Worry




Clover & Birdsfoot Trefoil