Once all 20 subsamples have been collected from a particular sampling area, thoroughly mix the cores into a uniform composite sample. If the soil is wet it may be necessary to dry it before mixing. After the sample is mixed, take a minute to sift through it and remove any foreign material. Finally, place approximately one pint of the soil into a sample box or bag for submission to the lab. Soil sample boxes and bags can be obtained from your local Michigan State University Extension county office.
In most cropping systems, sampling the soil every two to three years will provide enough information for sound nutrient management. Sandy soils with low cation exchange capacities can rapidly lose nutrients to crop removal or leaching, and as a result should be sampled more frequently. Due to the unique nutrient needs of many vegetable crops, it is recommended that fields with vegetables in the rotation be sampled at least every other year.
The Soil and Plant Nutrient Laboratory at Michigan State University offers two basic soil analysis services. Homeowners and gardeners can purchase a soil test self-mailer kit from their county Extension office for $25. This service includes a sample bag, postage paid envelope, complete lab analysis for pH, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), organic matter, soil texture and sulfur, as well as custom fertilizer and lime recommendations.
Commercial producers can purchase a soil sample box for $12. This service includes a basic soil analysis and report indicating nutrient concentrations and needs. The basic analysis package tests for pH, lime requirement, P, K, Ca and Mg, but a wide range of other analyses can be run at an additional cost. Fertilizer recommendations are not automatically generated for commercial producers, but can be obtained upon request from your local agriculture educator at no cost. Results from both the homeowner and commercial soil test services are usually returned within two weeks of sample submission.
Following the soil sampling procedures discussed above will help you collect a representative sample. Good samples improve the accuracy of analysis and fertilizer recommendations, providing a strong foundation for successful nutrient management.
For additional information on these sampling strategies, see MSU Extension Bulletin E-498, “Sampling Soils for Fertilizer and Lime Recommendations.”