Nitrate Toxicity in Drought-Stressed Corn Silage and Other Annual Forages

Sid Bosworth, Extension Associate Professor, Department of Plant and Soil Science, University of Vermont

A major concern with drought stricken corn is the potential for nitrate accumulation and toxicity.  Drought stricken fields of corn, sorghum and sudangrass are the most likely crops to accumulate nitrate, particularly those fields that are heavily fertilized with manure or nitrogen.  As crop growth slows down or ceases during periods of dry weather and drought, nitrates will often buildup in the soil.  When rain finally occurs and crop growth resumes, there can be a sudden uptake of the accumulated nitrate and for a while, plant nitrate levels will be higher than normal and pose a risk of toxicity to animals consuming the crop.  Below are a few suggestions for managing nitrate risk:

When to Chop Drought-Stressed Corn

Another question is "when do I chop?"  The answer depends on the condition of the corn.  If there was no pollination and fertilization of kernels, then the corn should be chopped as soon as whole plant moisture reaches 55% to 70% (depending on type of silo).  Be sure to test whole-plant moisture of chopped corn using either a microwave or a Koster moisture tester.

If pollination and fertilization of kernels did occur, then be sure the plants have a chance to reach the optimum maturity to maximize yield and quality.  Observe the kernels for maturity and monitor whole-plant moisture for 55% to 70% range.

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