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A recent survey of farmers by the Conservation Technology Information Center found that cover crops boosted corn yields by 9.6% during the drought year of 2012, and soybean yields by 11.6%. That’s compared to side-by-side fields with no cover crops.
However, cover crops can also lower cash crop yields if not managed correctly, warns Hans Kok, Conservation Cropping Systems Initiative, Indiana. In a dry spring, the cover crop may use up valuable soil moisture that the cash crop needs, says Joe Lauer, University of Wisconsin corn agronomist.
That’s why beginners should start small, Kok says. Instead of planting an entire field of cover crops, he suggests that first-timers put in a few strips at least as wide as the combine. “The combine yield monitor will show you if there is a yield difference.”
Cover crops' roots anchor the soil and nutrients when other crops aren't there to do the job. This is cereal rye.
What tillage practices are compatible with cover crops?
“Cover crops can work in any system,” Carlson says, but the best fit is with no-till, strip-till, or spring tillage.
Jim Zoss, the Illinois farmer, says cover crops worked very well in his strip-till system. He planted his first cover crop on Sept. 13, 2012, following early corn harvest. His goal was to capture N not used by the drought-stricken corn crop. Zoss drilled 50 acres of annual ryegrass alone, and 60 acres of annual ryegrass mixed with oilseed radish, at a seeding rate of 10 lbs./acre of annual ryegrass and 2 lb./acre of radishes. A week later, he planted 40 acres of oats after corn. He seeded the cover crops in 7.5-inch rows, capping every fourth row on the grain drill to create un-planted strips 30 inches apart. “The blank row is where we made our strips with RTK” later that fall.
Zoss got excellent stands of all three cover crops, spending about $12/acre for seed and $9/acre for drilling and labor. Unfortunately, most of the annual ryegrass died over the winter. However, he still had roots 18 inches deep, which helped hold the soil during last spring’s torrential rains. Zoss killed the surviving annual ryegrass with his regular preplant burndown of glyphosate plus Sharpen. “Then we planted as usual. There was no residue in the strips.”