In drought-stricken areas this year, corn yields may likely end up being measured by tons of forage, not bushels of grain. If you are going to chop or bale droughty corn plants for forage, or chop the crop for silage, what are the risks of causing nitrate poisoning when feeding the forage to cattle? The risk of having concentrations of nitrates in the forage that are high enough to cause problems are diminished when the corn crop is chopped for silage. The ensiling process and fermentation that takes place in the silo reduces nitrate levels, making the forage much safer for livestock consumption. However, "that's not the case if the corn crop is green chopped or grazed," says Steve Barnhart, Iowa State University Extension forage agronomist. For silage, if the crop is dying prematurely, the chopping decision should be made while there is still enough moisture in the stalks to properly ensile the crop. If no grain forms and the stalks remain alive, the silage chopping timing can be delayed.
If chopping drought-stressed corn, he suggests you follow these steps:
* Test for nitrates. Read the ISU fact sheet on nitrate toxicity and testing.
* Test crop moisture. Test the moisture of the chopped plant for proper ensiling to insure good fermentation. Good fermentation is important to reduce nitrate levels in the feed. Don't be fooled by how dry the drought damaged corn looks. It may still have too much moisture -- too wet to ensile.
To determine actual whole plant moisture you need to sample some representative plants from the field. Chop the plants, maybe run them through a chipper-shredder or other device. Test for moisture using the Koster moisture tester, or other method such as a microwave oven or heat lamp.