A major factor limiting the time of establishment after mid-June is the availability of moisture. 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.