End-of-Season Field and Sweet Corn Stalk Test


This test can be used to determine nitrogen deficiency, sufficiency, or excess in silage and grain corn, and in sweetcorn. The test is based on research in Iowa, Connecticut and Massachusetts. When N is in excess of the plants requirement, nitrate accumulates in the lower cornstalks and the extra N does not contribute to a greater yield. Rather, it can adversely crop growth, crop economics and the environment. When the plant is N deficient, nitrates are removed from the lower cornstalk during grain filling and an indicator of deficiency is the yellowing and drying of lower leaves. Similarly, an indicator of excess is lower leaves remaining dark green through to maturity.

The test can be used, to gain confidence in, the nutrient management planning process. It can be used to check availability of N from manure and the pre-sidedress N test (PSNT), and to calibrate the test for variations between fields. In certain years, cool wet spring years, the soil PSNT may indicate the need for N fertilizer when sufficient N may still be released from the manure and soil organic reserve. The stalk test can show you if fertilizer was needed and help you decide N application in future years.


Sampling Procedure

The test requires collection of corn stalks at end of season.

For sweetcorn collect stalk samples at time of picking ears or up to one day after ear harvest.

For silage corn collect stalk samples one week before silage harvest to one day after harvest.

For grain corn collect stalk samples between one and three weeks after black layer formation on 80% of kernels.

Cut an 8 inch segment 6 inches above ground level.

Collect samples from 15 plants for every 10 acre field or sweetcorn block.

Place in a paper bag (not plastic, this promotes fungus growth) and dry or freeze.

If you want us to analyze these for nitrates then include $10 per sample and send

samples to:

                                Soil Test Lab

                                West Experiment Station

                                University of Massachusetts

                                Amherst, MA 01003



Stephen J. Herbert

Dept. of Plant and Soil Sciences

University of Massachusetts

UMass Extension and s319 Nonpoint Source Pollution

CDL Publ. 01-8

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Last updated: 11/11/02.