Cotton following corn in rotation resulted in an average 8.9 percent to 17.1 percent yield increase compared to continuous cotton in a 12-year study at Mississippi State University.
Wayne Ebelhar, MSU research professor and agronomist, discussed the long-term research project at the recent Beltwide Cotton Conferences in San Antonio. The study was conducted on two sites, the Centennial Farm at Stoneville, Miss., where cotton has been grown continuously “for at least 100 years,” Ebelhar says, and the Tribbett farm, which is not as productive as the Stoneville location. Ebelhar says the yield advantage comes from “the rotation effect. All other factors were the same.”
“This was a technology-based study,” he adds. “We planted GMO varieties and hybrids to maintain what farmers would do.” He uses conventional tillage and irrigates the plots.
Results on the Tribbett farm show an 8.9 percent yield increase; the Stoneville location yield advantage is 17.1 percent. Cotton following corn resulted in a 230-pound yield increase, averaged across 12 years.
Ebelhar says the trial design is somewhat unique in that data are available much sooner than typical rotation studies, which “take a long time to see the results. We plant every crop, every year, replicated,” instead of planting one crop one year and following with a rotation crop the next year.
The average yield advantage also includes two years with negative yield results behind corn. “This rotation can reduce yields,” Ebelhar says. “Excessive rainfall during reproductive growth,” he says, results in “bigger plants, larger root systems and boll rot. We lost a lot of cotton.” That situation played out at both locations.
He also notes that one crop can affect a following crop because of different production practices. “We’ve seen some herbicide injury,” Ebelhar says.
The rotation scheme included continuous cotton; cotton, corn, cotton; and one plot that included soybeans in the mix — corn, soybeans, cotton and cotton. “Corn following soybeans has surpassed corn following cotton by 12.7 bushels per acre per year,” Ebelhar says. That’s a 6.5 percent advantage.
“In the Centennial Rotation, the cotton, corn rotation resulted in a 222-pound per acre per year increase, compared to continuous cotton.” That’s a 22 percent advantage.
Ebelhar also looks at nutrient uptake and removal in each of the rotation regimes. “Nutrient uptake and removal vary greatly, depending upon the crop yield during the growing season,” he says.
Across the 12-year Centennial Rotation study, total nutrient uptake for continuous cotton included (pounds per acre): nitrogen, 2,002.7; phosphorus, 262.9; potassium, 1,452; and sulfur, 300.4. Cotton and corn uptake was: nitrogen, 2,648; phosphorus, 427.8; potassium, 2,070.2; and sulfur, 361.1. Corn cotton rotation uptake results include: nitrogen, 2,869.4; phosphorus, 470.8; potassium, 2,254.5; and sulfur, 388.6. Corn soybean uptake results are: nitrogen, 3,626.2; phosphorus, 479.3; potassium, 2,452.3; and sulfur, 335.7. Soybean corn results are: nitrogen, 3,376.8; phosphorus, 444.6; potassium, 1181.6; and sulfur, 311.7.
Perhaps more important, Ebelhar says, is nutrient removal. Continuous cotton removes the least nitrogen, 801 pounds per acre over the 12-year trial. Other nutrient removal numbers include: phosphorus, 150.2; potassium, 413.1; and sulfur, 75.1. Cotton and corn removed 1,456.4 pounds of nitrogen; 300.9 pounds of phosphorus; 507 pounds of potassium; and 129.4 pounds of sulfur.
The corn cotton rotation removed 1,606.7 pounds of nitrogen; 333.7 pounds of phosphorus; 546.5 pounds of potassium; and 142.5 pounds of sulfur.
Nutrient removal for the corn soybean rotation resulted in a 2,610.5 pounds of nitrogen removal; 377.5 pounds of phosphorus; 737 pounds of potassium; and sulfur removal was 136.5 pounds. In the soybean corn plots, nitrogen removal was 2,440.1; phosphorus, 349.3; potassium, 689.5; and sulfur 126.3.
“Nutrient removal is much greater in rotation systems that have both corn and soybeans compared to systems dominated by cotton”’ Ebelhar says. He says the removal rate runs 70 percent to 200 percent higher in a grain system. “Stover/residue removal for bio-energy or feed-stocks, and residue burning could increase nutrient removal from the field.”
Growers using a rotation plan that includes cropping systems with varying levels of nutrient removal must know how those nutrient levels change. “Soil testing and monitoring nutrient removal is needed to maintain yields under high yield environments,” Ebelhar says.