Rolling cover crops
Most cover crops in Iowa are terminated with herbicide around or before planting of corn and soybeans. At the Practical Farmers of Iowa conference in January, three farmers talked about experimenting with a new way of terminating cover crops: rolling.
Most organic farmers in Iowa rely on tillage to kill their cover crops. Rolling, also known as rolling-crimping, is used elsewhere in organic systems where producers are looking to avoid tillage. When it works well, the practice has the added benefit of effectively suppressing weeds, as the terminated cover crop creates a thick mulch that inhibits weed seed germination.
The method relies on the rye life cycle to effectively terminate the plant. When the plant has reached “anthesis,” or partial flowering stage, it is most susceptible to being killed through mechanical means. Iowa State University researcher Dana Jokela explains how to identify anthesis stage: “There will be yellow pollen tubes visible all over the seed heads. Since rye seed heads do not all emerge at the same time, neither will they reach anthesis at the same time. It is advisable to wait until early-emerging seed heads are in full anthesis and late-emerging seed heads have at least a few pollen tubes visible, which usually occurs in late May or early June in Iowa.”
If rye is rolled before anthesis, it will just spring back up and continue to grow.
Roller crimper developed
Researchers at the Rodale Institute developed an implement called a “roller crimper” mounted on the front of a tractor; it works by knocking down and snapping the cover crop near the ground. The roller crimper is an expensive piece of equipment. The farmers presenting at the PFI conference all tried the technique with equipment they either had on-hand or could borrow.
Doug Alert of Hampton, Dave Schmidt of Exira and Francis Thicke of Fairfield talked about the equipment they used to try out the system. Thicke, an organic dairy farmer, rolled a cereal rye cover crop after drilling soybeans. The drill partially knocked down the rye (it had reached anthesis), and the culti-mulcher for rolling finished the job and laid the rye flat.
“I didn’t have quite as much rye biomass as I would have liked, but the rye mostly did a good job of controlling weeds,” he says. “The exception was in places where the rye mat wasn’t very good, which happened for several reasons. I think a Rodale-style roller crimper would have done a better job of laying the rye mat down evenly.”
Schmidt rolled a cereal rye cover crop ahead of a diverse summer grazing mix.
“Overall, it was a successful experiment,” he says. “The culti-mulcher we used was very effective killing the rye.” He’s still finding rye straw on the ground in February. “As far as protecting the soil goes, it’s amazing.”
The Rodale Institute recommends 6,000 pounds of biomass per acre to effectively suppress weeds. Schmidt is working on a trial with PFI to fine-tune the system this year to increase the amount of biomass. He has a mix of rye and vetch planted, and will be evaluating fall fertilization of chicken litter and its effect on biomass production in the rye.
Gailans is with Practical Farmers of Iowa.
This article published in the March, 2016 edition of WALLACES FARMER.
All rights reserved. Copyright Farm Progress Cos. 2016.