Drought is taking a toll on crops, writes Terry Mader, University of Nebraska animal science professor, at beef.unl.edu/. With little rain and depleted subsoil moisture in some areas, he says crops may not survive the growing season for fall harvest.
"In the present immature stage of growth, green chopping, haying, or grazing are options which can be considered for corn, sorghum hybrids and soybeans," Mader writes. "If silage is to be made, some fields could be ready by mid-August or earlier, after that the plant may become too dry for good fermentation to occur. Optimum plant moisture for silage is 65%."
Drought-damaged crops can be harvested as hay. With coarse-stalked crops, adequate drying time is needed. Plants will dry more quickly if crimped as they're cut. Since the stalks are coarse and leaves dry, corn plants in particular can be baled in round bales at around 20% moisture.
If tonnage is too low to mechanically harvest, drought-damaged crops can be grazed, he points out, but nitrate toxicity is a concern with corn and sorghum plants. Immature, drought-damaged plants are likely to be highest in nitrate content. If nitrates are a concern, grazing should be controlled and cattle removed from the field before they graze the lower portion of the stalk, where nitrate concentration tends to be heaviest.
In plants developed to near maturity but with very low grain yields, nitrates are usually less of a problem and these can be grazed more heavily. To decrease nitrates in hay and silage, raise the cutting height a few inches.
Many cattlemen feed drought-stricken crops as green chop. If the damaged crop is prone to being high in nitrates, take precautions to reduce the risk of livestock losses. A nitrate analysis is recommended. An analysis on the lower third of the plant prior to harvesting is a good indication of what the highest levels of nitrates may be.
If a nitrate analysis isn't conducted on the silage or green chop, Mader advises feeding it to a few animals for a couple of days while observing for toxicity problems, before offering it to the whole herd.
"Turning a few tester animals in first to screen for nitrates is a good idea if you're going to graze a drought-stricken field," he says.
Don't hold green-chopped corn or sorghum overnight, or let it heat or spoil. A delay in chopped forage will increase the conversion of nitrates to nitrites by bacterial action and increase toxicity several-fold. Chop and feed on a daily basis using a relatively coarse cut, and don't feed more than the cattle will eat in a few hours.
If green chop isn't needed immediately, it can be ensiled, as silage often loses 1/3 to 1/2 of its nitrate content once fermentation is complete. Of the harvesting alternatives available for immature drought-stricken crops, ensiling is preferred, Mader says.
He cautions producers to, before beginning any harvesting, check into any crop-insurance provisions that may apply. More info on nitrates and prussic acid may be obtained from your local Extension office.
Editor's note: You can learn more about drought management at www.beefcowcalf.com. Click on "Drought Management" from the list on the opening page.
-- Terry Mader, University of Nebraska