Nitrate is one of the major nitrogen (N) forms utilized by plants. Excessive nitrate accumulation can occur when the uptake of nitrate exceeds its utilization in plants for protein synthesis due to factors such as over nitrogen fertilization and stressful weather conditions.

If too much nitrate is accumulated in the forage crops, it can be toxic to livestock. Sorghum and millet have been noted as having a high potential for accumulating nitrate.

Producers should watch forage nitrate closely to avoid cattle fatality and to better manage their hay crop since we have seen many high nitrate forage samples this year.

Normally, drought stress, cloudy weather and other climatic conditions, as well as over- fertilization with nitrogen, will enhance nitrate accumulation in the plant. Below is a summary of our laboratory nitrate test results in July 2012. However, nitrate concentrations could get much higher as the hot and dry weather continues. It is important to have your hay tested.

Once hay nitrate is tested, follow the feeding guidelines highlighted in the table below. It is considered potentially toxic for all cattle when nitrate (not expressed in nitrate-nitrogen) in the forage is greater than 10,000 parts per million (ppm). Producers should avoid grazing or feeding high nitrate hays. More detailed interpretation can be found from OSU Extension Fact PSS-2903 Nitrate Toxicity in Livestock.

The most reliable way to find out nitrate in the hay is to collect a representative sample and have it tested by a laboratory. OSU Extension Fact PSS-2589 Collecting Forage Samples for Analysis highlights the proper techniques to collect forage samples. Samples can be submitted for nitrate and other forage quality analyses to the Soil, Water and Forage Analytical Laboratory in Stillwater through your local county extension office.

We normally have the results ready within 24 hours from the time when sample is received by the lab. However, many samples we receive at the lab were not sampled properly.

More attention should be paid on sampling standing forage, such as a haygrazer by following the right procedures:

  • Clip at least 20 representative plants at grazing or harvesting height from the suspected area. Cut the whole plants (include leaves and heads) into 2-3” long pieces, combine and mix well in a bucket.
  • Fill the cut sample into a forage bag. Use the quartering method to reduce the amount if there is too much sample to send to a lab.
  • Put the forage bag into a plastic bag will give you more accurate moisture content, but never put plastic bags inside our forage bags.