COLBY, Kan. -- This year many dryland cornfields will not produce enough grain to warrant combining costs. These fields, however, represent opportunities for cattlemen for silage, hay or grazing, a Kansas State University animal scientist said.
Regardless of the harvesting option, nitrates in the corn may be a problem, said Sandy Johnson, livestock production specialist with K-State Research and Extension.
A few areas have received some showers in the past few days, said Johnson, who spends her days working with livestock producers in northwest Kansas to provide research-based information and to find solutions to their challenges. For plants that are still growing, the showers cause nitrate concentrations in the plant to spike even higher as the plant uses the moisture to try and grow again, which brings in even more nitrogen.
"Do not harvest drought-stressed plants for 7 to 10 days after a rain to avoid this problem," Johnson said. "When you do harvest, the highest concentration of nitrates will be in the base of the plant so it is wise to raise the cutter bar to 6 to 10 inches. If you are grazing, remove the animals before they start grazing the lower portion of the plant."
Ensiling will reduce the nitrate content by 40 to 60 percent, she said. But if nitrates are four times the lethal levels before ensiling, reducing them to two times lethal levels may still create feeding challenges.
"Be sure to test silage and hay from drought stressed fields prior to feeding," the animal scientist said. Take 20 or more core samples from each field to get an accurate representation of what́s there. Nitrate levels will be highly variable across a field and will be impacted by fertilization practices.
"If you elect to graze these fields, remember that weeds present in the field such as kochia and pigweed are also nitrate accumulators," Johnson said. "At my house, these have started growing again with a recent shower and are very high in nitrates. The four-foot tall or less corn stalks that have bent over and dried up may also be a problem for grazing. As these plants are relatively immature, they are very palatable clear to the ground and the few I have tested show problem levels of nitrates throughout."
If grazing looks like a good option, but weeds and short burnt up areas are worrisome, Johnson suggests that producers consider inoculating their cows with a bacteria capable of reducing the toxic effects of nitrates.
"A product called Bova-Pro can be given as a bolus or feed additive 10 days before feeding high nitrate feedstuffs," she said. "The loss of a single cow or one or more aborted fetuses would pay to treat a lot of cows. I recommend that producers consider Bova-Pro as a risk management tool for high nitrate feedstuffs. They should check with their veterinarian or feed store for details and availability."
Similar nitrate concerns exist for any sorghum-sudan type forages growers may be considering harvesting, she said.
"Always know what you are feeding before you feed and make sure animals are full when you change diets," Johnson said.
A planning spreadsheet is available to help producers evaluate the grain versus silage option at http://www.oznet.ksu.edu/drought/ or by contacting a county or district K-State Research and Extension office.