Dry weather across the state has increased concerns about nitrate accumulation in forage plants.

North Dakota State University specialists warn about the effects of rain on drought-stressed forages.

When soil moisture conditions are favorable, and plants are actively growing, they absorb nitrate from the soil and convert it into amino acids and proteins. When plants become stressed by dry weather, growth slows, but the plant may continue to take up nitrates.

Because plant growth has slowed, the nitrates taken up are not converted into amino acids and proteins at the same rate. Instead, nitrates accumulate in the plant, increasing the risk of nitrate poisoning, says James Rogers, NDSU Extension forage crops production specialist.

Some farmers could assume that when it rains, and the plant begins actively growing again, nitrate levels suddenly drop. Rogers says that’s not true.

“Following a rain event, nitrate levels may actually spike two to three days after the rain,” says Rogers.

He says it can take several days for the plant to convert accumulated nitrates into proteins and amino acids.

“Before grazing, allow seven to 12 days of good growing conditions to give plants an opportunity to reduce nitrate accumulations,” recommends Rogers.

The same advice applies to harvesting hay. Plants should be given an opportunity to recover and actively grow before harvesting for hay.

“Even after allowing a seven- to 12-day recovery period following a rain event, do not assume that nitrate concentrations in forage have dropped to a safe level,” says Karl Hoppe, NDSU Extension livestock systems specialist.

Livestock drinking water can also contribute to nitrate toxicity and should be considered when determining the overall risk.

“Of the nitrate test results received so far this year, approximately half would be considered generally safe for livestock feeding,” says Hoppe. “The remaining half could be utilized if limited in the ration or, in some cases, if limited in the ration and fed only to nonpregnant animals.”

When blending hays, Hoppe also recommends knowing the nitrate levels of all hays included in a ration. Blending hay with a known nitrate concentration with hay of unknown nitrate concentration can lead to unintended results.

Forages should still be tested for nitrates following a rain event, says Ashley Ueckert, NDSU Extension agriculture and natural resources agent in Golden Valley/Billings County.

“Your NDSU Extension county agent can offer advice and assistance with forage nitrate testing,” says Ueckert.

For more information from NDSU Extension specialists about dealing with nitrate spikes, visit ndsu.ag/nitrate-spike26.

For recent articles about the dry summer and forages, visit ndsu.ag/nitrate-summer26 and ndsu.ag/FM-drought26.

For more information about nitrate poisoning, read the NDSU Extension publication “Nitrate Poisoning of Livestock.”

NDSU Agriculture Communication – Aug. 14, 2026

Source: James Rogers, 701-857-7677, james.rogers.1@ndsu.edu

Source: Karl Hoppe, 701-652-2951, karl.hoppe@ndsu.edu

Source: Ashley Ueckert, 701-872-4332, ashley.ueckert@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu