Grazing Residue: Having Your Cake and Eating It Too
Integrating crop and livestock enterprises provides a competitive advantage to farmers and ranchers, said Warren Rusche, SDSU Extension Cow-Calf Field Specialist.
“Residue grazing is an example of how integrating crops and livestock results in a ‘win-win,’” Rusche said. “Corn stalk grazing represents an opportunity to cut feed costs for ranchers, or serve as a source of supplemental income for crop farmers, without hurting yields next year.”
He added that the increased acres of corn results in greater quantities of residue available for feed. “Because the land cost is charged to the crop enterprise, crop residues are much less costly than either summer pasture or harvested feeds,” he said.
Rusche explained that crop residue grazing works extremely well for cows in mid-gestation. “Because cows will select the higher quality husks, leaves and any whole ears left in the field they should not require additional energy or protein supplementation as long as they are not forced to consume poor-quality portions of the plant, such as the stalk,” he said.
Even cattle with greater nutrient requirements, such as growing calves or replacement heifers, Rusche said will perform well grazing stalks when provided supplemental protein.
What about the effects of grazing corn stalks on next year’s crop?
One of the barriers to greater use of corn stalk grazing is the belief in some circles that grazing stalks will reduce yield the next year resulting in less net income.
The University of Nebraska recently published the results of a 10-year study on the effects of grazing corn stalks in the fall on soybean yields the following year in a no-till system.
In those studies, soybeans planted after corn stalks which were grazed in the fall yielded about 3 bushels more compared to ungrazed corn stalks. “The same pattern was shown in a one-year comparison at the SDSU Southeast Research Farm, although those differences were not statistically significant,” Rusche said, referencing Table 1.
Another common concern is that grazing stalks will remove too much residue and greatly affect soil organic matter. “The long-term yield results from Nebraska would suggest that this has not been a significant problem in that system, but it is possible to estimate the quantity removed compared to the amount of residue produced,” he said.
For every bushel of corn, there is approximately 45 pounds of residue. The husks and leaves represent about 16 pounds of that total. If a 1,400-pound cow consumes 2.5 percent of bodyweight per day, in 30 days she would eat about 1,050 pounds of husks and leaves.
However, not all of that organic matter leaves the field.
Forty to 50 percent of the husks and leaves are indigestible, meaning that of the 1,050 pounds consumed, about 400 pounds return to the field as manure for a net removal of 650 pounds.
A field that yields 150 bushels per acre will produce 6,750 pounds of total residue. In that case, the 650 pounds removed represents only about 10 percent of the total.
“Keep in mind that if the field is not grazed or tilled, the husks and leaves are more likely to be blown into the ditch or fenceline,” he said.