Kat Caswell, Agronomy Specialist
Grazing corn stalks in the fall and winter is an excellent way of integrating livestock onto cropland. Research from UNL has shown that grazing corn stover has no immediate impact on the following crop yield in a typical year. Corn stover provides an alternative source of forage for cattle, and an additional source of income from fields that would otherwise be dormant in the winter. Grazing livestock does not remove the total amount of nutrients from the field that bailing stover does, as a portion of the nutrients consumed during grazing are returned to the field through manure. Nor does grazing remove the same amount of corn residue that baling does. While grazing corn stover can be beneficial, there are some important considerations to keep in mind.
For general soil conservation, at least 50% ground cover should be left after grazing. With the high price of feedstuffs, there might be the temptation to graze as much as possible from corn stalks this winter. While there may be no impact on next year’s crop, over time the greater removal of corn residue will decrease soil carbon and impact soil quality. Avoid heavily grazing areas where soil is already prone to erosion. One year of heavy grazing on easily eroded soils can decrease the amount of time it takes for water run-off to occur, increasing the risk of loosing both soil and nutrients from the field. After serval years of drought, unusually high winds, and short but intense storms, preventing soil erosion should be a concern.
As with pasture or rangeland management, determining an appropriate stocking rate is important. The amount of grazable forage (stalks, leaves, husk, and cob) after corn harvest is directly related to the amount of harvested grain. In fields where corn yields have been decreased due to drought, there will be less forage available for grazing this year. UNL Extension has a Corn Stalk Grazing Calculator available to assist in determining the stocking rates for your corn residue (see below for link and website directions).
The concentration of nitrates are highest in the lower third of the corn stalk. Stalks are generally not the first forage cattle graze but leaving animals to graze for a longer period this year may lead animals to consuming toxic levels of nitrates. Nitrate toxicity is a higher risk in dryland fields than in irrigated fields. Corn stalks on the edge of irrigated fields may have higher nitrate content than the rest of the field.
For example, a field that typically produces 100 bu/acre of corn would produce around 1,600 lb of dry matter per acre, meaning there is 830 lb of dry matter available for grazing. If an 1,000 lb animal eats roughly 26 lb of forage a day, there would be approximately 30 days of grazing available. If the corn yield was only 50 bu/acre, the available grazing period for a 1,000 lb animal is now 15 days. Grazing that field with the same 30-day period as you would have in the past, will remove a greater amount of residue and increase the likelihood of soil erosion.
Previous studies have shown that that is little impact of grazing on soil compaction. When compaction did occur, it did not reach levels where plant root growth would be impeded, nor did the last through the following year. If compaction around a single area is a concern, try rotating the location of supplemental feed and minerals to encourage animal movement.
In conclusion, grazing corn stalks can benefit both cropland and cattle. Following lower corn yields due to drought, adjust the grazing period length, stocking rate, or amount of supplemented feed to reduce the risk of soil erosion, nutrient loss, and nitrate toxicity. While one year of heavy grazing may not impact the following crop’s yields, be aware the risk of water erosion and loss of residue on future management.
For more information on UNL Extension’s Corn Stalk Grazing Calculator
- https://beef.unl.edu/learning/cornstalkgrazingcalc.shtml
- Go to beef.unl.edu à Educational Resources à Learning Modules à Feeding and Nutrition Management à Corn Stalk Grazing Calculator