“Nitrate accumulation occurs in a plant when it is injured and is not able to convert nitrate to protein efficiently after a hail storm,” explains Barry Yaremcio, beef and forage specialist at the Alberta Ag-Info Centre.
“In non-legume crops, water and nutrients are pushed into the plant from the root system at the same rate after the storm as was provided prior to the hail event. 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.”
Soil fertility - in particular the soil nitrogen content - and stage of crop development are critical factors when determining a nitrate accumulation problem in the plants.
“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 on soil nitrogen available in the soil well into July. A crop that is thick with high yield potential would use up 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,” he says.
He adds that hay crops tend to have lower fertility than annual crops, and the risk of a hay stand having high nitrate concerns is much lower than an annual crop.
“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, so it is extremely rare to have nitrate accumulation in legume forages.”
Feed testing labs can test for nitrates. Says Yaremcio, “If the sample is taken the fourth day after the storm, the results will indicate the worst case situation. Talk to the lab and request a rush analysis, and the results could be available one to two days after the sample is received.”
Yaremcio adds that ensiling will not reduce nitrate levels if the salvage crop is put up properly. “Adequate amounts of packing along with 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 then its quality is greatly reduced.”
For properly made silage, the overall quality of the chopped material going into the pit should be the same as the silage that is fed later in the year.
“Taking one handful of silage out of each truckload as it is unloaded at the pit provides a good representative sample,” he explains. “From this sample, a nitrate test and other nutrient tests can be done. Put each handful into a plastic pail with a lid. At the end of the day, mix up the sample and collect a half bread bag full to send to the lab. Squeeze the air out of the sample, seal and freeze the sample before sending it away. Send the sample in for analysis on a Monday or Tuesday so it gets to the lab without being in transport over the weekend.”
“Nitrate in a forage or silage can be managed so that there are no problems or difficulties encountered during the feeding program,” adds Yaremcio. “Talk to your feed sales person or company nutritionist, nutritional consultant, or contact the Ag-Info Centre and talk to a livestock specialist.”
Source : Alberta.ca