Source: Practical Farmers of Iowa
Farmer-cooperator Tim Sieren compared soybean seeding dates relative to cover crop termination (before and after) as well as cover crop termination techniques (chemical vs. roll-crimp). “If I can manage a roller-crimper system in soybeans, while maintaining yields,” Sieren said, “I could drastically reduce herbicide use.”
Soybean yields were mostly affected by cover crop termination date (table below). Regardless of soybean seeding date, yields were greater on average by 10.5 bu/ac when the cover crop was terminated with herbicide on May 5 compared to roll-crimping the cover crop on May 30.
Roll-crimping the cereal rye cover crop proved to be a challenge. “The rye needs to be roll-crimped before the planter goes through, not after,” Sieren said. “I didn’t have a heavy enough stand to crimp down, and stay down (possibly due to the May 17 hailstorm). It didn’t kill all the rye, and after 2 weeks, you couldn’t tell it had been crimped, and it stayed greenish until I finally hit it with glyphosate 2 weeks later. Then it died and the beans finally acted like they wanted to grow.”
When Sieren waited to roll-crimp the cover crop on May 30, soybean yields were similar between the May 7 and May 30 seeding dates, but they were also less than when the cover crop was chemically terminated on May 5. With the May 30 cover crop termination (roll-crimp), Sieren achieved yields equivalent to his county’s average with only a single in-season herbicide application on June 27.
For more details on this trial, read the full report: Roll-Crimping Cover Crops and Soybean Seeding Date. This project was supported by the Iowa Department of Agriculture and Land Stewardship, Division of Soil Conservation.