Yields of corn and soybean are higher when planting is rotated from year to year, says University of Missouri Extension agronomist Bill Wiebold.
Wiebold speaks about his 20-plus years of rotation and tillage research at the MU Crop Management Conference, Dec. 15-16 at the Holiday Inn Executive Center, Columbia.
Online reservations are still accepted at http://plantsci.missouri.edu/cmc for the conference, which is held in conjunction with the MO-AG winter convention and trade show.
Wiebold found soybean yields drop by 9 percent when soybean is not rotated with corn. Farmers should weigh that yield loss when making cropping decisions, he says.
Missouri farmers plant 3 million acres of corn and 5 ½ million acres of soybean annually. No other state in the Midwest reports that high a ratio of soybean to corn.
This means that some farmers, for a variety of reasons, do not rotate crops annually. Missouri’s soil and weather combination and profitability top the list.
Yield loss occurs immediately when crops aren’t rotated, Wiebold says. Farmers who plant corn one year and soybean the next realize no loss. When they follow with soybean a second year, a 9 percent loss happens immediately.
“It doesn’t matter what was planted two years ago,” Wiebold says. What farmers planted the year before affects yield.
Corn yields also benefit from rotation. Rotated corn produces 12 percent more bushels per acre than continuous corn.
“Every other year works,” Wiebold says. “It’s simple but it works very well for our Missouri farmers.”
Despite more than two decades of research, Wiebold and other agronomists don’t know why the yield drop is immediate. “We know rotation works, but we don’t know why,” he says. “It’s still a mystery.”
At the conference, Wiebold will also present research on the results of long-term tillage. His research dates back to when governmental agencies began recommending a switch to no-till farming. Wiebold’s studies show that soybean and corn grow well in no-till fields, even in poorly drained soils.
Since farmers adopted no-till practices, soil erosion dropped from 8 ½ tons per acre to about 4 tons per acre. About one-fourth of Missouri’s tillable ground is no-till.
The crop management conference offers three tracks of offerings. Topics cover management of crops, nutrients, pests, and soil and water.
Robert Paarlberg of Harvard University opens the conference at 8 a.m. Tuesday, Dec. 15, with a keynote address on “Our Culture War Over Food and Farming.”