Be Aware of the Risks of Nitrate Accumulation in Annual Forages this Year

Casey Guindon and Nicole Santangelo PennState Extension

Challenging weather conditions in some areas of the state may lead to nitrate accumulation in summer annual crops like corn silage, forage sorghum, and sorghum-sudangrass hybrids this fall.

Sorghum testing positive for nitrate should be retested with a forage analysis for confirmation. In the meantime, follow feeding recommendations for high nitrate forages. Image Credit: N. Santangelo.

Dry weather conditions in many parts of the state have led to concerns for the potential of nitrate accumulation in warm-season annual forages like corn silage, forage sorghum, and sorghum-sudangrass hybrids. Nitrate poisoning is observed most frequently when these forages experience drought stress followed by a significant rainfall event. This is especially true of fields with heavy manure rates or high rates of nitrogen fertilization. Under these conditions, nitrates accumulate in the lower portion of the plant and can be toxic when consumed in large concentrations, or in combination with drinking water with a high nitrate content. The only way to determine if high nitrate levels are present in the forage is with a plant analysis.

There are several practices that can help to mitigate potential issues with nitrate toxicity. The best option is to delay harvest until conditions have passed. After a significant rain event, it is advised to wait at least 3-5 days to harvest. Increasing the cutting height of the forage can also help to reduce overall nitrate concentration as most of the accumulation is in the base of the plant. Finally, fermenting the forage has been found to reduce nitrate concentration in the forage by about half over the period of fermentation. These annual forages are well suited to store as baleage or silage.

Any forages suspected of high nitrate levels should be tested prior to feeding. If forage quality testing reveals a high level of nitrate, it may still be possible to feed these forages on a limited basis by diluting them with forages with lower nitrate levels. The Penn State article High Nitrate Potential in Corn Silage, provides some feeding recommendations for these forages based on nitrate concentration. Consult a veterinarian or qualified nutritionist to discuss options.

While many nitrate feeding issues can be resolved by ensiling forages, high nitrate levels pose a risk to producers this harvest season. Nitrogen dioxide is formed in the silo when nitrates in plants combine with oxygen. This gas is dense and sinks into low-lying areas in the silo or attached feed room. Inhaling this gas can result in chronic respiratory problems, fluid buildup in the lungs, or, at high levels, instant death. The highest risk period for gas formation is 12 to 60 hours after filling the silo, but gas may be produced for up to 3 weeks. Be sure to aerate enclosed areas well if it is necessary to reenter the silo.

This article, including its text, graphics, and images (“Content”), is for educational purposes only; it is not intended to be a substitute for veterinary medical advice, diagnosis, or treatment. Always seek the advice of a licensed doctor of veterinary medicine or other licensed or certified veterinary medical professional with any questions you may have regarding a veterinary medical condition or symptom.


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