Drought will impact nitrates in corn plants
By Janet Kubat Willette
jkubat@agrinews.com
Date Modified: 08/13/2012 12:53 PM
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ROCHESTER, Minn. — The drought that's gripping 80 percent of the contiguous United States will impact nitrates and animals, veterinarian Steve Ensley said at a Minnesota Agriculture and Nitrates meeting on July 25.
Drought stress increases nitrate in forages because plants are unable to go through normal photosynthesis, said Ensley, of Iowa State University's Veterinary Diagnostic and Production Animal Medicine Department.
Iowa has already had its first reported case of death loss from cattle being fed corn that was green chopped and fed immediately, he said.
It's important that farmers take steps to make sure drought-stressed forage is safe to eat. Good fermentation will decrease nitrate levels, Ensley said. It's usually safe to feed corn silage that's been fermented for 30 days.
He advises that farmers sample to determine where nitrates are in their corn plants. If the nitrates are in the lower part of the plant, raising the cutter bar will lower the nitrate in the feed.
Nitrates in stalks could also be a problem for producers who intend to graze their beef cattle on harvested corn fields that were drought stressed. Ensley recommends field testing stalks before turning the cattle out on the field.
For forage, 1 percent nitrate on a dry matter basis is potentially lethal to ruminants. Horses, pigs and dogs are at less risk. Nitrite is the poisonous compound in nitrate.
Another drought impact comes from farmers hauling water to pastures in tanks, oftentimes the same tanks used to haul nitrogen-based fertilizer. Ensley told farmers to avoid using the same tanks.
Earlier this month in Iowa, a producer hauled water to his pasture using the same tanks after he'd thoroughly rinsed them. In an hour, 28 of his 60 head were dead.
It's just impossible to clean the tanks out good enough to use them to carry fresh water, Ensley said. Usually, the water has 5,000 to 6,000 ppm nitrates in the tank.
The latest government recommendation for livestock is that nitrates in water should be 440 ppm or less. The drinking water standard for humans is 10 ppm.