Tilley column: Beware of high-nitrate levels when cutting corn

Published 12:00 am Wednesday, September 28, 2011

Rowan County farmers reached a crossroad this year when it came to harvesting corn. Due to the hot weather and lack of much-needed rainfall throughout the reproductive stages, many farmers came to realize that their corn was not going to produce an ear, thus not economically suitable to harvest for grain.
Many farmers were forced to cut their corn crop for silage. However, many who decided to follow this alternative harvest method realized they still would have to face the consequences of the dry weather.
When it comes to cutting corn for silage, the first thing on many farmersí minds is nitrate levels. High nitrate levels in corn silage can be harmful to both humans and livestock. When dealing with livestock, symptoms of nitrate poisoning include labored breathing, loss of weight and a lack of appetite.
Another issue some farmers may face is the buildup of silo gas, which can be harmful to humans. According to North Carolina State extension specialists Dr. Ron Heiniger and Dr. Jim Dunphy, corn silage stored in silos that contains high nitrates can mix with organic silage acids to form nitrous oxide. Nitrous oxide decomposed with water can then form nitrogen oxide, dioxide or trioxide. Many factors can affect nitrate accumulation in silage feed. There are many to review, but large amounts of nitrogen fertilizer, the type of drought experienced and the growth stage at which the crop felt the affects of dry weather should be taken into consideration.
Farmers should not be alarmed or worried when it comes to handling high nitrate silage. There are many ways to lower nitrate levels in corn to a safe feeding level. First, allow the silage to complete its fermentation process. Fermentation can reduce nitrate levels by 30 to 50 percent. Second, when cutting silage, raise your header and try to leave a 6- to 8-inch stubble. Corn that suffered from drought will accumulate nitrates within the first few inches of the stalk. Finally, try to add other grains, hay or other feeds to your silage. This can dilute nitrate levels when feeding. Corn silage that is less than 1,000 ppm of nitrates are safe to feed.
At the end of the day, if the farmer is still not satisfied and believes he or she may be facing a nitrate problem, always send in a forage sample to the North Carolina Plant Testing service.
For more information on high nitrate levels in corn silage or for more information on sampling your feed, please call Scott Tilley at 704-216-8970 or email scott_tilley@ncsu.edu.