StettlerLocal.com Jul 21, 2022 @ 5:15pm
Hail storms at this time of year can damage annual and perennial crops. In some cases, the damage is minimal, and in others, catastrophic. There are guidelines to avoid nitrate accumulation when salvaging damaged cereal, oilseed, or hay crops.
An injured plant cannot convert nitrate to protein efficiently after a hail storm. In non-legume crops, water and nutrients are pushed into the plant from the root system at the same rate as before the storm. As a result, nitrate accumulates in the top leaves of the plant 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. Therefore, submitting a sample collected four days after the storm for nitrate will indicate the worst-case situation.
Nitrogen content in the soil and stage of crop development are critical factors in determining whether or not nitrate accumulation can occur. Crops such as canola and wheat have high application rates of nitrogen fertilizer. If the crop is thin and not overly productive, there could be significant amounts of soil nitrogen available in the soil well into July. On the other hand, a thick crop with high yield potential would use most of 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.
Hay crops typically have lower fertility than annual crops. Therefore, the risk of a hay stand having nitrates accumulate is much lower than annual crops. Alfalfa and legume crops (peas, clovers, vetches) 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 is extremely rare to have nitrate accumulation in legume forages.
Ensiling a damaged crop may not reduce nitrate levels. However, adequate amounts of packing, sealing with plastic as soon as possible, and allowing the silage to ferment for three to four weeks produces a stable product. Silage that is poorly made can reduce nitrate levels, but the quality of the silage is greatly reduced.
Nitrate in forage or silage can be managed to prevent problems during the feeding program. Here is a link to a publication that explains nitrates and how it impacts animals. https://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex851/$file/0006001.pdf
Barry Yaremcio
Ruminant Nutritionist