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8 Ways Cover Crops Pay

Take a good look at any idle land in your area. Left unchecked, it will soon proliferate with weeds. 

That's Mother Nature at work, says Paul Jasa, engineer in biological agriculture systems at the University of Nebraska-Lincoln.

 "Mother Nature keeps the ground covered, and a living root in the soil, for nine to 10 months each year. Then we came along and started doing tillage to grow crops. By growing corn or soybeans, we keep a living plant on the soil surface just five months or so each year," says Jasa, who spoke at a UNL Cover Crop Field Day near Humboldt, Nebraska last month.

Adding a cover crop program to the cash crop system does much to extend the life of the soil, by keeping the soil "livestock," or microbes, active throughout the year.

 Roots and residue are food for the living creatures in the soil, which also recycle nutrients, help to aggregate soil and ultimately, boost organic matter - which also improves rainfall percolation. 

Why should I plant?

Jasa, who has studied cover crop adoption and no-till systems for more than two decades, says farmers need to understand why they want to grow cover crops. 

The reasons are numerous:

  • Erosion control: Covers absorb raindrop impact. Oats planted in the fall, for example, provide quick cover yet winterkills, eliminating a need to apply herbicide for cover crop termination. 
  • Nutrient capture/recycling: Several species - by themselves or in a mix - can root down, then bring nitrogen back to the soil surface as the crops break down. 
  • Improved soil health: Roots and residues feed microbes, which are integral to soil health. "Otherwise, soil is just sand, silt, and clay particles," Jasa says. 
  • Water management: If soil can't store off-season precipitation, it makes sense to use it, he adds. "Unprotected soil is prone to evaporation loss due to the sun and wind. Properly managed cover crops can save precipitation," Jasa explains. 
  • Biodiversity: Just as humans enjoy a variety of foods, so do soils. Farmers who mix up the crop species feed the soil in different ways. 
  • Nitrogen fixation: Jasa says before World War II, farmers grew much of their own nitrogen. The advent of relatively inexpensive commercial fertilizers enabled farmers to quit growing legumes, if they wished. Now, with nitrogen costs on the rise, the ability to offset the cost of fertilizer by growing a legume cover crop is gaining favor. "Nitrogen is the only nutrient a cover crop can fix," Jasa cautions. "Deep rooted covers can redistribute other nutrients, but you'll still need to fertilize." 
  • Reduced compaction: Purveyors of radishes and turnips often tout the ability of these crops to break through hardpans. Jasa reckons that may be a bit oversold. "Deep tap-rooted plants need moisture to go through those hardpans," he says. "But any deep tap-rooted crop will work. It doesn't have to be a name brand turnip or radish." 
  • Weed suppression: You've no doubt noted that bare spots in fields don't stay bare for long. Weeds will come up and cover the soil. "Mother Nature is an opportunist," Jasa explains. "Our research shows that cover crops provide excellent weed suppression." For example, studies at the Rogers Memorial Farm near Lincoln, Nebraska, show that a cool-season cover crop can prevent establishment of marestail flushes; a dramatic finding when growers are working to combat herbicide-resistant marestail. 

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