Published in the Chat 'n Chew Café (3 Aug 1999). Also published in the Purdue Pest Management & Crop Production Newsletter (6 Aug 1999).

Drought Stress & Corn Silage Decisions

R.L. (Bob) Nielsen
Agronomy Department, Purdue University
West Lafayette, IN 47907-1150
Internet address:

Corn in parts of Indiana and much of Ohio continues to struggle with the effects of prolonged dry weather, compounded with the effects of the recent heat wave. Some corn growers are beginning to wonder whether marketing their corn as silage through their cattle would be more profitable than harvesting the stressed fields for the grain. Others who always intended to make silage now wonder whether they should be concerned with high nitrate levels in the corn plants. Some factors need to be considered during the decision-making process, as well as after the decision is made to make silage.

Potential Grain Yield.

Producers should not be too hasty in writing off a drought-stressed field as a loss in terms of its grain yield potential. As witnessed during the Great Droughts of '88 and ‘91, corn has an uncanny ability to produce grain under the worst of conditions. Be sure to sample worrisome fields thoroughly in order to estimate grain yield (see accompanying article) before deciding to harvest it as silage.

Government Program and/or Crop Insurance Considerations.

Before harvesting the crop for either silage or grain, be sure to check with your county USDA office and/or insurance agent for any red tape that needs to be handled regarding the effects of drought stress on the crop.

Value of Drought-Stressed Corn Silage.

Drought-stressed corn can be salvaged as silage with reducing gain in the feedlot. Value of the drought-stressed silage is better than expected because much of the carbohydrate that would have gone into the grain is stored instead in the stalk and leaves. Protein levels in drought-stressed corn silage may actually be greater than in normal silage.

Harvesting For Green Chop.

If you are considering green chopping the corn to feed directly to animals, be sure to note the harvest restrictions for any pesticides that have been applied to the crop. This includes insecticides as well as herbicides. Check the pesticide label or consult your chemical supplier for details.

Drought-stressed corn with little or no grain produced on the cob may contain unusually high levels of nitrates in the stalk. Green-chop forage from severely stressed corn should be tested for the presence of nitrates before feeding to animals. Quantitative laboratory analyses can be performed at Purdue's Animal Disease Diagnostic Laboratory. Call ADDL at 765/494-7440 for costs and other details for submitting samples. ADDL’s Web site URL is If nitrate levels in the green-chop forage are excessively high, then contact Kern Hendrix, Animal Science Department, 765/494-4832, Email: , for guidelines in feeding such high nitrate forage.

Harvesting for Silage.

If you decide to harvest drought-stressed corn for silage, the absolute first step is to determine the moisture content of the crop. For proper silage fermentation, the crop should not exceed 65% moisture. Stalks of plants with many or most of the leaves dead from stress can still contain considerable moisture levels.

A quick and dirty way to determine whether moisture content is suitable is to hand-squeeze a representative sample collected from the forage chopper. If water drips from the sample as it is squeezed, the corn is still too wet for proper fermentation. Growers can also determine moisture content of corn silage with a microwave oven. See Extension publication ID-172, "Use of Microwave Drying to Determine Moisture Content in Forage", available from your local Purdue Cooperative Extension Service office. This same publication is available on the Web at

Nitrate content of corn harvested for silage should not have to be a worrisome consideration. Forty to sixty percent of nitrates present in the stalk material will be eliminated during the ensiling process. However, various nitrogen oxide gases are produced in the process that are highly toxic to humans and livestock. For about the first 4 weeks after ensiling, do not enter a silo without first running the blower for 15 to 30 minutes.

For More Information, ask for a copy of NCH-58, "Utilizing Drought-Damaged Corn", at your local Purdue Cooperative Extension Service office. The Web address for this publication is

Corn Growers GuidebookFor other information about corn, take a look at the Corn Growers Guidebook on the World Wide Web at

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