Grazing corn residue proves its worth
Corn growers considering grazing cattle on no-till corn residue don’t have to worry about compaction, according to University of Nebraska (U of N) research. Yields of subsequent crops don’t suffer either from grazing of the previous crop’s aftermath. If anything, grazing of the residue could slightly increase yields of subsequent crops.
“Many crop farmers are concerned that cattle trampling will adversely affect soil physical properties and subsequent crop productivity,” says Mary Drewnoski, U of N beef systems specialist. “Our studies have found that grazing in late fall or winter does not result in biologically significant compaction on cropland or in negative impacts on subsequent crop yields.”
What the Study Found
A recent three-year study looked at the effects on soil properties and subsequent crops of three corn-residue treatments:
• Control, where residue was left on the field
Six cooperator sites from across the state were selected for the research. All but one of the sites were in no-till. Four were irrigated, and two were in dryland production. Some sites were in continuous corn production; some were in a corn-soybean rotation.
“Our goal for the grazing treatments was to take only 12% to 15% of the residue,” says Drewnoski. “Cows are selective grazers, and they’ll eat the husks and the leaves first. These are the most nutritious components of the corn residue and make up about 30% of crop aftermath. If cows have to start eating the stalks, they will no longer be able to maintain their body condition.”
In the grazed treatment, actual residue reduction was just under 20%, according to measurements taken in the spring following the grazing of the cows in November, December, and January. The grazed treatment had 77.5% cover, the baled treatment had 45.8% cover, and the control treatment had 88.7% cover.
“Some of the residue is lost due to wind, and with grazing, some is trampled into the soil surface,” she says. “The trampled residue combined with manure from the cattle returns about 90% of the dry matter from the residue back to the soil. In more long-term studies of cattle grazing corn residue, we see increases in soil microbial activity. That may contribute to the yield bump we see in the subsequent crop.”
The stocking capacity for grazing corn residue depends on corn yield. “Corn is consistent in terms of the relationship between stover and corn yield,” says Drewnoski. “We suggest stocking fields at a rate of one cow for one month for every 100 bushels of corn. You can increase the stocking rate when shortening the grazing period.”
In Nebraska, the customary fee for grazing corn residue is $15 per acre, assuming a corn yield of 180 bushels. “That provides grazing for one cow for about 54 days, at a cost of 28¢ per day,” she says. “That’s less than a quarter of the cost of feeding hay. The cattle owner typically provides water and checks the cows.”
Potential roughening of the soil surface from the hooves of the livestock can be avoided by matching grazing time to surface cover. Fields that are just being transitioned to no-till are best grazed in December or January, when the surface is frozen. Because of their more stable surface structure, long-term no-till fields can be grazed in late fall or early spring, when periodic thawing softens the surface.
Such a grazing strategy also prevents a potential temporary increase in penetration resistance at the soil surface that could impact the performance of seeding equipment in spring.
“Grazing cattle is a way for crop farmers to generate additional income and a way for cattle producers to reduce wintering costs,” says Drewnoski.”