Test Annual Forages for Nitrates

By PR Extension Office

As annual forages are being cut for hay, it is important to test for nitrate levels, according to Powder River Extension Agent Mary Rumph.

“This is a year when I wouldn’t expect nitrate levels in cereal grains to be high…however, we have had some samples, especially triticale, that are surprisingly high. These samples have been prior to the dough stage in development, so I’m hopeful that the levels will drop as the plants mature,” said Rumph.

High levels of nitrates in cereal grain are often present under drought conditions; however, any time the plant is stressed, high levels can occur. The roots of growing plants will continue to take in nitrate nitrogen; however, normal plant metabolism which convert nitrate to protein is disrupted and high nitrate levels accumulate. Any time the plant is stressed, nitrate levels can increase. Other contributing factors can be hail, fertilizing or planting on a field that was previously in alfalfa.

At normal levels of nitrate in the soil, the nitrate content is usually higher in young immature plants and decreases as the plant matures. The nitrate is usually highest in grain hay harvested before the dough stage of development. As the plant approaches maturity, the nitrate content usually decreases to well within safe feeding levels. Waiting until the soft dough stage can significantly decrease nitrate levels. Winter wheat is much less likely to accumulate nitrate compared to spring grains, although a few samples tested have also been higher than expected. Oats tend to accumulate nitrate more than most other cereal forages.

Under “normal” conditions, nitrate levels can be lowered by avoiding cutting or grazing when nitrate concentrations are at peak levels. Peak levels occur in the morning; delay haying or grazing until the afternoon on a sunny day. Under the current conditions of high heat and low moisture, there might not be a “safe” time according to Rumph.

“Bottom line, test your annual forages, if not prior to cutting at least sometime before feeding,” encouraged Rumph.

At the Extension Office, forage samples can be screened for nitrate levels. The screening test is a good place to start and can indicate whether more time is needed for the crop to mature. Samples of standing crops should contain approximately 20 plants (taken randomly by traversing in a zigzag pattern across a field) cut off about 4 inches above the ground. If the screening test indicates a high level of nitrate, a sample can be sent into the MSU Analytical laboratory for further testing. For more information on nitrate toxicity of forages, go to https://powderriver.msuextension.org/Agriculture.html or contact the Powder River Extension Office at 436-2424 if you have questions.