Soil tests can save homeowners money and improve growing results by helping accurately determine fertilizer rates and the need for soil amendments, such as compost. The Lewis and Clark County Extension Office can assist with sampling advice and tools, mailing samples, and interpreting results.

Collecting a sample

  • Remove any mulch or lawn thatch before collecting your soil samples.
  • Collect samples from multiple areas around your yard, garden, or field.
  • Soil samples are best collected using hand probes or augers (available at the Extension Office) or bulb planters to obtain the same amount of soil from each depth and location. The key is to get an even cylinder.
  • Collect soil to a depth of 6 inches.
  • The office needs a quart size bag full of soil.
  • Samples may be collected at any time, but it is best to wait at least two months after fertilization to give the fertilizer a chance to dissolve, disperse and be used by plants. If you take the sample in the fall, keep in mind that you will have more available nitrogen in the spring along with other nutrients than what your analysis indicates.

Sending samples for testing

  • The Extension Office uses Midwest Laboratories for soil analysis. Results generally take about 10 days and are sent via email unless requested otherwise.
  • Soil samples are $20 for a Basic Sample:
    • Organic matter, nitrogen, phosphorus, potassium, soil pH, magnesium, sodium, soluble salts, excess lime. 
  • Soil samples are $30 for a Complete Analysis including vital plant micronutrients: 
    • Organic matter, nitrogen, potassium, phosphorus, soil pH, sodium, sulfur, zinc, manganese, iron, copper, boron, soluble salts, cation exchange capacity, and excess lime. 
  • We only accept Cash or Check (made out to Lewis and Clark County Extension).

Reading the results