I received a panicked call from one of my clients early in the morning a few days ago. An orange-brown stream of gas was creeping along the ground in front of a bag of corn silage that he had been filling. Several dead birds lie on the ground near the bag. Fortunately for my client they were literally the “canaries in the coal mine”. He had not seen deadly silo gas or nitrogen dioxide before, but the dead birds were a clue that he shouldn’t go near it.
Silo gas is heavier than air and displaces oxygen in enclosed areas like silo chutes, causing suffocation. When inhaled, the nitrogen dioxide combines with moisture in the lungs to form nitric acid, which is deadly. In the still morning air that day, the gas did not disperse.
Silo gas is more likely to form when forages contain high levels of nitrates. Nitrate accumulates in the plant when environmentally stressed conditions reduce yields. The available nitrogen is not metabolized normally by the plant.
The extreme drought conditions in the Southern plains are stressing crops. Even irrigated corn is suffering, since dry rivers are often the source of irrigation. Another dairy client is contemplating plowing up a part of his corn crop because of lack of water. A recent nitrate test was over 19,000 ppm. Anything above 4,000 ppm should not be fed.
But, Drs. Bill Seglar and Bill Mahanna at Pioneer Hi-Bred caution that if there is any green left in the plant at all, it may be better to wait and hope for rain than to plow it up and plant a “rescue crop”. The established crop is usually a better bet. That’s a tough decision when you watch your corn crop lay dormant, especially when it contains toxic levels of nitrate.
However, a crop can turn around quickly if environmental conditions return to normal. Wait 3-5 days before chopping. Nitrate levels will be reduced by up to 50% during ensiling. Also consider raising the cutting height to 12 – 18 inches, since nitrate accumulates in the lower part of the stock.
Hopefully, Mother Nature will be kinder to the drought stressed Southern plains and the flooded Northern plains during the latter half of the summer.