Released: March 18, 2002

Wheat Yields Boosted By Rotation With Row Crops

MANHATTAN, Kan. – Farmers sometimes plant wheat in a rotation with row crops because it’s an advantage to the row crops, but the rotation can also boost wheat yields, according to a Kansas State University researcher.

"Sometimes wheat is thought to be in a rotation only because row crops can be planted no-till into wheat stubble so easily," said Mark Claassen, Agronomist-in-Charge of the K-State Research and Extension Harvey County Experiment Field. "But wheat benefits from being in a rotation with row crops compared to continuous wheat. The one exception is when wheat is planted no-till after grain sorghum harvest."

Claassen’s research at the Harvey County Experiment Field near Hesston is still under way, but is far enough along to develop some conclusions. In the study, crop rotations were combined with tillage treatments. The rotation treatments were wheat-corn; wheat-sorghum; wheat-soybean; continuous wheat; and continuous sorghum. The tillage treatments used on the row crops were: V-blade [V-blade, sweep-treader and mulch-treader] and no-till. Wheat was planted no-till after row-crop harvest.

The continuous wheat had three tillage treatments: burn, which consisted of burning, disking and field cultivating; chisel, with chisel, disk and field cultivator; and no-till. The continuous sorghum had chisel [chisel, sweep-treader and mulch-treader] and no-till treatments.

Averaged over all tillage treatments in the study, wheat in the wheat-soybean rotation had the greatest yield at 57.5 bushels per acre, followed by the wheat-corn rotation at 54.9 bushels. Continuous wheat averaged 44.1 bushels and wheat in the wheat-sorghum rotation fared the worst at 39.5 bushels.

This research did not address why wheat performance of no-till wheat after sorghum was lackluster, but other studies have shown similar yield declines, said K-State agronomist Jim Shroyer.

According to Claassen, the decline is thought to come from the presence of certain chemicals in sorghum stalks, and may be influenced by differences in soil moisture and/or residual nitrogen differences.

Other research at Hesston indicates that the negative effects of sorghum on wheat can be minimized by keeping seeding and nitrogen rates high, for example both between 90-120 pounds per acre.

In the wheat-corn and wheat-sorghum rotations, tillage treatments on the row crops had little effect on wheat yields, Claassen said.

"Interestingly, in the wheat-soybean rotation, the five-year average wheat yield for the V-blade tillage treatment was 5.8 bushels per acre lower than the no-till wheat yield," Claassen said. "However, the significance of this difference remains to be verified by additional years of data."

In continuous wheat, the five-year yield for the burn treatment was 46.9 bushels per acre, while the chisel and no-till treatments averaged 42.9 and 42.6 bushels per acre, respectively.

"By the way, sorghum in the sorghum-wheat rotation yielded 97 bushels per acre – 19.9 bushels more than the continuous sorghum yield of 85 bushels," he said, noting that this effect should be "considered in weighting the merits of the wheat-sorghum rotation."

In the continuous wheat, as in any monoculture, pests became a problem, and in this study, cheat was a serious weed problem. It was corrected by using the currently non-labeled herbicide, Olympus.

"Although we don’t recommend continuous no-till wheat, this research indicates that stacking no-till wheat for two years in a rotation may be successful if weeds are controlled and a wheat variety with tan spot disease resistance is used," Claassen said.

When stacking is done, Claassen said it is usually advised touse longer rotations with a larger diversity of crops.

-30-

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Mary Lou Peter, Communications Specialist
mlpeter@oznet.ksu.edu
K-State Research& Extension News