Grazing Residue: Having Your Cake and Eating It Too
Integrating crop and livestock enterprises represents an incredible competitive advantage for farmers and ranchers.
By: Warren Rusche, SDSU Extension Cow/Calf Field Specialist
Increased acres of corn result 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.
When to Consider Residue Grazing
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 (i.e. the stalk). Even cattle with greater nutrient requirements such as growing calves or replacement heifers will perform well grazing stalks when provided supplemental protein.
Effects on Next Year's Crop?
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 next year in a no-till system. In those studies soybeans planted after corn stalks 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 (Table 1).
Impact on Soil Organic Matter
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.
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 1400-pound cow consumes 2.5% of bodyweight per day, in thirty days she would eat about 1050 pounds of husks and leaves. However, not all of that organic matter leaves the field. Forty to fifty percent of the husks and leaves are indigestible, meaning that of the 1050 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 6750 pounds of total residue. In that case, the 650 pounds removed represents only about 10% 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.
Integrated Crops & Livestock: A "win-win"
Residue grazing is an example of how integrating crops and livestock results in a “win-win”. 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.
