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Seasonal Disorders

Mineral uptake is seasonal, and is impacted both by management and environment. Grass tetany is a magnesium deficiency associated with cool-season grass grazing in the spring. Grass tetany is rarely a problem in New York State. Nitrate poisoning results from high rates of N fertilizer application to grasses, in association with cool temperatures, drought, or other plant stress situations. Nitrate levels in grass will peak about 2-3 weeks following application. A forage nitrate concentration of about 1000 ppm nitrate-N or less is safe to feed as the primary forage in a ration. Prussic acid poisoning can occur with most sorghum species with immature, wilted, frosted or stunted plants. Sorghum species with prussic acid should not be grazed or fed green-chop if less than 15-18 inches tall. High rates of fertilizer increase the problem. Sorghum silage and hay are generally safe from prussic acid poisoning.