Understanding MSU soil test report basics – Part 2 of 2

These tips on interpreting your MSU soil test report can help you make best use of your fertilizer investment.

Once you have submitted your soil sample and received your MSU soil test report, the next step is to use the Michigan State University Soil and Plant Nutrient Laboratory’s information to put together a practical, economical plan for providing the needed nutrients. Michigan State University Extension educators are qualified to help with this. Many farm supply businesses have knowledgeable people who can provide advice or a “second opinion,” but the bottom line is it is your decision – and you are paying for it.

To help with the process, here are some of my observations based on many years of helping farmers and gardeners across the Upper Peninsula interpret MSU soil test reports.

Understanding the MSU soil test report

  • A good guide for understanding the details of the MSU soil test report can be found at MSU Soil and Plant Nutrient Laboratory.
  • Your report includes information on soil pH and lime index, phosphorus, potassium, magnesium, calcium and a few calculated values including cation exchange capacity and percent of exchangeable bases. The “regular” soil test does not test for soil nitrogen content. Plant-available nitrogen is very mobile in soils, depending on water, soil temperature and other factors. Your report will recommend nitrogen based on the crop and yield goal specified. For corn, nitrogen rate will include consideration of the price of fertilizer and the price of corn.
  • The lime index number relates to the soil’s resistance to change in pH. The lime index usually falls between 70 and 60. If a soil has a lime index of 70, then lime will not be recommended regardless of pH. As the lime index decreases below 70, more lime will be required to bring the pH back up to 6.5, compared to a soil with a higher lime index.
  • You will notice the soil nutrient levels are presented as a number and graphically. The graphic representation includes three sections: “Below Optimum,” “Optimum” and “Above Optimum.” Any report listing a nutrient level in the “Below Optimum” range will include a nutrient recommendation including nutrients to support the yield goal and additional nutrients to build up the nutrient level in the soil. However, when fertilizer prices are high or commodity prices are low, a temporary option when nutrients are in the “Below Optimum” range is to apply only the nutrient removal rate. Nutrient removal information for many crops can be found in “Nutrient Recommendations for Field Crops in Michigan,” MSU Extension publication E2904, and “Fertilizer Recommendations for Vegetable Crops in Michigan,” MSU Extension publication E550B.
  • Phosphorus and potassium recommendations are generally given in pounds of P2O5 and K2O per acre. This is not the same as pounds of fertilizer per acre. These figures need to be converted into a practical fertilizer application rate.
  • Nutrients recommended on the soil test report may not match up with common, locally-available, pre-blended fertilizers. You may need to have fertilizer custom blended by your dealer, settle for a “best-fit” available fertilizer or mix fertilizers yourself. Be sure to consider the cost of all options.
  • If manure is applied to the field, it is in your interest to take credit for all nutrients applied in the manure and reduce your fertilizer rate accordingly. A note included on the soil test information sheet should specify the type of manure, such as liquid dairy, sheep, beef cows, etc., and amount applied per acre (gallons or tons). If a manure nutrient test is not available, “book” values from Midwest Plan Service’s “Manure Characteristics” can be used. Be sure to consider the Michigan Right to Farm Manure Management and Utilization and Nutrient Utilization GAAMP (generally accepted agricultural management practices) as you decide how much manure and fertilizer to apply.
  • If farming organically, the MSU soil test report is a very useful tool. Be sure to provide a note indicating you are farming organically or “naturally” and don’t want to use “chemical” fertilizers. Many Extension educators are familiar with organic farming systems and can provide alternatives for organic plant nutrient sources.
  • In case you decide to change the crop to be grown, you can use the same soil test data to generate a fertilizer recommendation for another crop. The MSU Fertilizer Recommendation Program is a simple, online tool to do this.

Part 1 of this article includes tips on collecting a good soil sample for testing.

Soil testing is a small investment with potentially large rewards. If you’ve never soil tested, consider testing one of your problem fields to get started. Contact your local MSU Extension field crop, vegetable or fruit educator for commercial soil test reports. For home gardening and landscape soil test reports, contact the MSU Extension toll-free hotline at 888-678-3464.

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