Cover-up grows in popularity
Seeding cover crops to enhance basic rotations is a new frontier in Nebraska cropping systems, according to its adherents. Interest has grown in the past few years in trying seedings of one or two cover crops or a cocktail blend of several after wheat harvest in summer or even after taking off soybeans or corn in the fall. As yet, acreage remains limited.
At a glance
• Farmers build soil by using cover-crop cocktails.
• Blends of grasses, legumes and brassicas are used.
• They talk of multiple benefits, including capturing nitrogen.
“We are trying to provide a healthier soil for crops,” says Brian Berns of Bladen. “Cover crops do that by increasing soil biological activity and increasing organic matter. The key is having something growing for more months of the year. We’re feeding the soil microbes, bacteria and fungi, even the earthworms.”
Brian and brother, Keith, are no-tillers who’ve experimented with more types of cover crops than anyone in the state. They used a USDA Sustainable Agriculture Research and Education grant to do most of their evaluations.
They market a base seed mix, called Green Cover Soil Builder, which is a 10-pound-per-acre blend of grasses, legumes and brassicas. “We like a balance of these plants for the diversity and benefits they provide,” Brian says.
The Bernses’ base blend consists of sorghum-sudan, a grass; lentils and common vetch, legumes; and oilseed radishes, canola and a hybrid brassica. “You can add to this blend seed from your own farm, such as oats, sorghum or soybeans,” Keith says.
The mix increases soil biological activity and also provides forage for livestock. Plus, the legumes can fix nitrogen, while the brassicas scavenge any excess soil nitrogen, and their tap roots break up compaction and leave soil cavities that increase water infiltration.
The best route to success, at least for cover-crop blends, is planting them into wheat stubble, giving them a longer growing season for establishment.
Seeding a blend after soybeans or corn in the fall is riskier because of the shorter window for establishment, but it can still work if moisture conditions are adequate.
Winter annual grasses, such as wheat and cereal rye, provide erosion control and also can scavenge excess nitrogen. Then the following spring, after a burndown herbicide, they decompose and release nutrients for the next crop.
While cover-crop cocktails are relatively new, use of single or double cover crops isn’t. Producers chopping silage, particularly on light-textured soils, have for years seeded rye, wheat or triticale as a soil cover and for winter pasture, says Paul Jasa, University of Nebraska engineer. A number of cattle producers have planted turnips or other brassicas for forage.
Seed corn growers, who harvest earlier than other corn producers, have used brassicas, including turnips and radishes, to scavenge excess nitrogen. That’s intended to prevent leaching from fields that often are over-fertilized and over-irrigated, particularly if it’s seed corn rather than a regular corn-soybean rotation.
“Today, there is increasing interest in cover crops, but we’ve not established trends or clear-cut recommendations as to the best systems or best mixes,” Jasa adds.
The Berns brothers list the following benefits cover crops provide for no-tillers:
• protect from wind and water erosion
• build soil organic matter
• aid soil structure and capture carbon
• feed earthworms and soil microbes
• provide root structure to help precipitation penetrate deeper into the soil
• fix nitrogen with use of legumes
This article published in the February, 2010 edition of NEBRASKA FARMER.