Corn growers who want to salvage drought-damaged fields for livestock feed should do it carefully because of the potential for high nitrates in the forage, warns a University of Illinois Extension educator.
“Levels will be highest in fields that received high nitrogen fertilizer or manure applications and in plants that are severely stunted and did not form ears,” says Robert Bellm.
Nitrates are highest in the lower third of stalks, so harvesting or grazing only the upper two-thirds of plants will greatly reduce the potential for nitrate toxicity. Forages with high nitrate levels might be fed safely if diluted with grain or other low-nitrate feeds.
“Within limits, animals can be conditioned to consume high-nitrate forages as long as they are introduced to them slowly, allowing them to acclimate to the high nitrate levels,” says Bellm.
But grazing and greenchopping are risky; ensiling is preferred because it significantly reduces nitrates, say Bellm and Mike Hutjens, animal science professor emeritus at the university. Baling the crop as hay also won’t reduce nitrate levels, Hutjens adds.
He offers these strategies for dealing with droughty corn:
● Don’t harvest it too early. If corn plants have green, active tissue, they may recover and produce more yield if rain arrives.
● Immature, drought-stressed corn can appear dry and dead but may contain more than 70% moisture in the stalks. For optimal fermentation, ensile when the dry matter in the chopped material ranges from 30 to 38%, depending on type of storage. In bags, bunkers and piles it can be wetter, while in upright storage it must be drier.
● Adding a silage inoculant to improve fermentation is recommended because naturally occurring bacteria may be low. Do not add urea or limestone – it can slow fermentation.
● The silage may have 60-80% of the nutrient value of normal corn silage, depending on the stage of maturity. It should be tested for nutrient content and nitrate levels after ensiling.
“Livestock producers may be able to purchase drought-stress corn locally as it has little value for grain or hog producers,” says Hutjens. “Like livestock producers in the southwestern areas of the U.S. last summer, dairy managers are asking what will be available and affordable for their cattle. Drought-stress corn silage may be an alternative locally.”