Nitrogen applications should be split - half when plants begin to grow in May and the rest in early July. Livestock toxicities Nitrate toxicity Heavy nitrogen fertilization followed by drought is the most common situation that causes nitrate accumulation in forage. Shading and cool, cloudy weather can also contribute to this problem. These environmental conditions result in nitrate accumulation because growth is limited while nitrate uptake continues. In cattle, nitrates are reduced to nitrite in the rumen.
Nitrites are toxic to livestock because they interfere with the ability of blood to carry oxygen.
The rate of nitrate incorporation in plants is regulated by the nitrate reductase enzyme. Molybdenum is a key part of nitrate reductase. If plants are deficient in molybdenum, nitrate reduction is inhibited, potentially resulting in nitrate toxicity. The availability of molybdenum to plants is determined by soil acidity. Nitrates are typically concentrated in the lower portion of the stem, so care should be taken to keep animals from consuming large amounts of the lower part of the stalk of these forages when nitrate concentrations may be high.