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Maximizing Cover Crops

Cover crops have traditionally been used as a method to improve soil health while reducing erosion and suppressing weeds. An increased interest in utilizing cover crops for livestock grazing has resulted in two recent University of Idaho Extension research projects.

In Idaho, growers have sought assistance from UI Extension on rotating cover crops in as an annual crop and interseeding approaches that allow the cover crops to grow along with the cash crop.

Improving Soil Health

Cover crops play an important role in agriculture. They are planted to provide living ground cover, either during or in between rotations of the primary crop. Research has shown that cover crops help minimize soil erosion, prevent the leaching of important plant nutrients, suppress weeds and increase crop diversity.

In addition to these agronomic benefits, using cover crops for grazing can also provide an economic advantage and help mitigate the effects of climate change. Cover crops can help hold spring and fall soil moisture from evaporation and properly managed livestock provide a less expensive source of nutrients to the soil. A grazed field of cover crops provides soil nutrients from both cover crops and the distribution of livestock manure.

Reducing Fertilizer Inputs

UI Extension educators are working with a grower near Picabo, where crop rotation is severely limited by the climate. The producer hopes to plant cover crops in the annual rotation to use as rent income from grazing. This will allow the producer to reduce commercial fertilizer inputs in the following season’s barley crop, and help improve marginal soils.

Results show that annual cereals can be used with cover crop species in an intensive grazing situation from June-November.

“The project worked really well, better than we thought it would,” said Steve Hines, UI Extension educator and advisor on the project. “We did learn some things. One, that it’s viable. Two, he needed a lot more cattle in there than he had. He was running 150-200 head and could have used a whole lot more cattle to stay ahead of those cover crops.”

Test strips in this year’s barley crop included varying amounts of nitrogen. Hines and colleagues Lauren Golden, Joel Packham and Carmen Willmore will harvest the barley to determine if using the cover crops for grazing provides a fertility boost for the barley crop.

“We would like to continue that work,” Hines said. “For me, as an applied researcher, one year’s worth of data doesn’t really tell you much except for what happened that year. I would like to see it applied over two-three years in rotation with his other crops.”

Interseeding Corn Silage

A second UI Extension project involves interseeding a cover crop mix into standing corn silage on a farm in the Raft River area. Interseeding is the practice of planting cover crops between the rows of already growing cash crops to increase the amount of time for the cover crops to grow before winter.

“Their goal is two-fold,” Hines said. “One, when they cut corn silage off there is not a lot left on those fields. They would like to have something on there to help hold the soil through the winter. And two, to provide additional feed for their dairy cattle and beef herd.”

Researchers hope to determine the optimal time of the growing season to plant the cover crop seed into the standing corn.

“The idea of interseeding in the summer is that, once that corn is off, the cover crop is already there,” Hines said. “As opposed to planting it after the corn is off and then trying to get it up and going before winter.”

Hines and his research partners are in the second year of the study. In the first year, they planted the cover crop into plots that were 12 corn rows wide by 350 feet long. The cover crops grew well, but the harvest equipment used for the corn silage damaged the small test plots.

“Even though they did grow into October, they had a lot more damage than what a field completely covered would have,” Hines said.

Additional plots were planted this season and data will be finalized after harvest. Hines said early evidence suggests that the middle of June, before the canopy shades out the ground, seems to give the cover crop the best chance to get started.

Partners in Research

Growers like those in Picabo and Raft River are vital to the success of UI Extension research projects, Hines said. By providing access to their farms, researchers like Hines can conduct experiments at a working scale.

“When we go to winter schools or talk to producers about this stuff, if we have done this on a farm, their reception of it is a lot different than if we do it on a research farm on small plots,” he said.

UI Extension has also partnered with the Natural Resources Conservation Service to develop the Magic Valley Soil Health Forum, a group including agency professionals and growers that meets monthly during the winter to discuss soil health and cover crop topics.

“We get together and basically talk,” Hines said. “What did they try that year, what worked, what didn’t, what would they like to see us research? It’s a good opportunity to provide a network of local growers and agency personnel.”

For Hines, building relationships with growers is one of the most rewarding aspects of his job.

“I like getting out on the farms,” he said. “I really enjoy the opportunity to take an idea and see it work and then see producers start doing it. That’s what Extension is all about, that’s our job. To find ways to help guys apply new ideas and new technology and see it work.”

Tufts of grassy plants grow between the corn stubble.
Interseeding test plot of cover crop mix on harvest day. The crop was planted into standing corn in mid-June.
Tufts of grassy plants continue to grow between dried up rows of corn stubble.
Interseeding test plot of cover crop mix three weeks after harvest. The crop was planted into standing corn in mid-June.

Article by Amy Calabretta, College of Agricultural and Life Sciences

Published in September 2018.

University of Idaho Extension

Physical Address:
E. J. Iddings Agricultural Science Laboratory, Room 52
606 S Rayburn St.
Moscow, ID

Mailing Address:
University of Idaho Extension
875 Perimeter Drive MS 2338
Moscow, ID 83844-2338

Phone: 208-885-5883

Fax: 208-885-6654

Email: extension@uidaho.edu

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Barbara Petty