Watch for nitrate accumulation after a hailstorm

Water and nutrients, including nitrogen, are pushed into non-legume crops after hail damage

There are many things to consider when salvaging a damaged cereal, oilseed, or hay crop after a hail event.

One of them is nitrate accumulation, which occurs in a plant when it is injured and unable to convert nitrate to protein efficiently after a hailstorm.

In non-legume crops, water and nutrients are pushed into the plant from the root system quickly after the storm. Nitrate accumulates in the top leaves and concentrations peak roughly four days after the injury. If the plants recover and new growth is observed, nitrate levels can return to normal 12 to 14 days after the injury.

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“Soil fertility, in particular the nitrogen content in the soil and stage of crop development, are critical factors as to whether or not there will be a nitrate problem in the plants,” said beef and forage specialist Barry Yaremcio. “Crops such as canola and wheat have high amounts of nitrogen fertilizer applied.

“If the crop is thin and not overly productive, there could be significant amounts of soil nitrogen remaining in the soil into July. A crop that is thick with high yield potential would use up the available nitrogen much earlier in the growing season. With less nitrogen left in the soil, there is less available to be transported into the plant and thus less risk for nitrate accumulation.”

Hay crops tend to have lower fertility than annual crops.

“The risk of a hay stand having high nitrate concerns is much lower,” said Yaremcio. “Alfalfa and legume crops have nodules in the root system that regulate nitrate transport into the plants. The nodules only allow as much nitrogen into the plant as is needed — therefore, it’s extremely rare to have nitrate accumulation in legume forages.”

Feed test labs can test for nitrates.

“If the sample is taken the fourth day after the storm, the results will indicate the ‘worst case’ situation,” he said. “Talk to the lab and request a ‘rush’ analysis. The results could be available one to two days after the sample is received.”

Ensiling the crop will not reduce nitrate levels if the product is put up properly.

“Adequate amounts of packing, sealing with plastic as soon as possible, and allowing the silage to ferment for three to four weeks produce a stable product,” said Yaremcio. “Silage that is poorly made can reduce nitrate levels, but the quality of the silage is greatly diminished.

“To get a representative sample when the silage is being made, take one handful of silage out of each load as the trucks unload. Put each handful into a plastic pail and keep the lid closed as much as possible.

“At the end of the day, mix up the sample and collect a half bread bag full, squeeze out the air, and freeze the sample. Send the sample in for analysis on a Monday or Tuesday so it gets to the lab without being in transport over the weekend.”

Bottom line is that nitrate in a forage or silage can be managed so that there are no problems encountered during the feeding program, he said.

A fact sheet called Nitrate Poisoning and Feeding Nitrate Feeds to Livestock is available at www.agriculture.alberta.ca.

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