Soil Sampling Frequently Asked Questions

Why should I soil test?

Soil testing is an important diagnostic tool to evaluate nutrient imbalances and understand plant growth.

The most important reason to soil test is to have a basis for intelligent application of fertilizer and lime.

Testing also allows for growers and homeowners to maintain a soil pH in the optimum range (6.0-7.0), which keeps nuitrients more available to the plant for growth.

Protection of our environment - we cannot afford to pollute our surface and ground waters by indiscriminate application of phosphorous or nitrogen fertilizers, for example.

Cost savings - why apply what you don't need?  Soil test results provide information about the soil's ability to supply nutrients to plants for adequate growth, and are the basis of deciding how much lime and fertilizer are needed.

What is being tested in a soil sample?

The regular soil test includes determination of soil pH, available phosphorus, potassium, calcium, and magnesium levels as well as recommendations for lime and fertilizer.  Other soil tests are available at supplemental costs, such as organic matter, zinc-manganese, etc.

How do I know if the test results are accurate?

The lab takes various quality control measures to ensure the accuracy of results.  Soil with predetermined nutrient levels is tested every 20 samples to provide an accuracy check.

We recommend testing soil every 3 years.  If recent results are not consistent with past results, notify your county Extension Educator or the lab within one month to rerun the questioned test.

Why doesn't the regular soil test include nitrogen analysis?

Soil nitrate levels are the best indicator of nitrogen availability.  Because these levels fluctuate widely depending on rainfall and soil temperature, the best time to take soil nitrate samples in while the crop is growing within two weeks of supplemental nitrogen applications.

A soil sample taken months ahead of this time will not provide an accurate measure of the nitrogen available to the plants.

How does the lab make nitrogen recommendations?

Nitrogen recommendations are based on the past and present crops grown plus the yield goal for the crop to be grown.

Less nitrogen is recommended when the previous crop was a legume, because they add nitrogen to the soil.

Where can I get my soil samples tested?

Soil samples should be mailed to:

Michigan State University
Soil & Plant Nutrient Laboratory
East Lansing, MI 48824-1325

How soon should I receive test results?

You should receive test results in about two weeks.  The analysis takes 3 to 5 working days from the time the lab receives the samples.

The results are then mailed to the Extension Office and to the person sending the sample.

Remember, recommendations are in pounds of nutrient needed, not pounds of fertilizer to be applied.