Soil nitrate test for corn in Michigan

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Nitrogen is the nutrient that most affects corn growth and grain yield. Nitrogen necessary for the corn crop comes from two primary sources; the soil and supplemental N added to the soil. Commercial fertilizers are the primary sources of supplement N, but animal manures may be a significant source on farms with livestock operations. Soil N comes from the decomposition of soil organic matter and crop residues, which may include legume or non-legume cover crops. Net N released from the soil will vary depending on soil organic matter content and soil moisture and temperature conditions. The new corn N recommendations are based on numerous N rate studies across Michigan using N rates from 40 to 240. In these studies the N requirement of the corn crop was met by a combination of N released from the soil and the applied fertilizer N. Therefore, the new MRTN (maximum return to N) N recommendations have built-in some credit for N, which becomes available in the soil. More productive soils release more N from the soil than less productive soils. This tends to bring the N recommendations for high yielding soils and for lower yielding soils closer together than one might expect.

As the result of the N recommendations for corn having a built-in credit for soil N release, the N credits based on the presidedress soil N test have been modified. The PSNT N credits are now indexed as follows:

Soil nitrogen credit for corn in Michigan.
Soil testing for corn

These credits apply only for corn and MRTN nitrogen rates.
** Soil contains adequate available nitrogen for growing the corn crop. No additional nitrogen is needed.

Cost of a soil nitrate analysis by the Michigan State University Soil and Plant Nutrient Lab is $10.00 per sample ($13.00 for nitrate and ammonium). Each sample should represent no more than 20 acres. See the MSU Soil and Plant Nutrient Lab website ( for additional information.

MSU Soil and Plant Nutrient Lab
A81 Plant and Soil Sciences Bldg.,
Michigan State University
East Lansing, MI 48824-1325

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