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Big Push is to Capture Nitrogen with Cover Crops

Big Push is to Capture Nitrogen with Cover Crops
Big Push is to Capture Nitrogen with Cover Crops.

Staunch soil conservationists have always believed in cover crops for winter protection on sloping lands. However, as the 'fence-row-to-fence-row' farming of the '70s took over, cover crops limped to the sidelines. Now they are making a comeback, which started with the introduction of annual ryegrass a few years ago, and which now seems to be picking up steam very quickly.

"It's about capturing nitrogen that would otherwise be lost over winter," says Barry Fisher with the Natural Resources Conservation Service. "What happens is that nitrogen left over by the crop goes into tile lines and winds up at places where they don't want out nitrogen. That's what the hypoxia issue in the Gulf of Mexico is all about."

More people are trying various covers to see which might be good at trying up the nitrogen in the fall and holding it for use later, Fisher says. Roger Wenning, Greensburg, has experimented with various cover crops. Some work better than others. On most of his acreage, however, he plants a cover crop and then either strip tills or no-tills into it in the spring. At the same time, he is building soil organic matter instead of losing soil to erosion.

"We had a big rain and the next day water coming off my farm was clear," he recalls. "Water coming off fields where they moldboard plowed or did other conventional tillage were brown and muddy. Looking down into my pond, which caught a lot of water in that storm, you could see my dock steps 6 inches under the water- it was that clear."

Part of the change in attitude toward cover crops is learning how to sue the nitrogen that is immobilized temporarily by soil organisms. That process prevents the nitrogen form being lost. However, it also means that nitrogen isn't available when the corn first emerges in the spring. "It becomes available about the grand growth to pollination stage, when you really need it," Fisher says.

What you need to do is apply enough starter N to get the crop through the stage where the N is immobilized. Then you are back in business, he notes.

More people are applying starter fertilizer on no-till fields today. Some apply a mix of 10-34-0 and straight 28% N. Anything that provides enough N to get the crop through the early season until the once-immobilized N is free and available will do the job, Fisher notes.

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