Enthusiasm toward cover crops and the benefits they can provide to the nation’s agriculture soils was palpable during the first National Conference on Cover Crops and Soil Health. More than 300 researchers, agronomists, farmers and teachers attended the invitation-only event held Feb. 17 to 19 in Omaha, Neb.
Sustainable Agriculture Research and Education (SARE) has an ambitious goal: 20 million acres of cover crops on U.S. soils by 2020.
Cover crops serve multiple purposes, according to Rob Myers, director of the North Central Region of the SARE organization, which co-sponsored the event. They can build organic matter, reduce soil compaction, reduce erosion and, if implemented with other managerial changes to a farm, lead to lower production costs.
Most importantly, a farm that implements cover crops can do much to boost soil health, a priority within the USDA’s Natural Resources Conservation Service. Conference organizers cite some soils in Iowa that have lost as much as 5 percent organic matter in the last 50 years. Yields of corn and soybeans continue to increase throughout the nation, but these increases come at a significant cost to soil health. Implementing management techniques such as conservation tillage and cover crops can help reverse that trend.
Adoption of cover crops into a crop rotation somewhat mimics the action Mother Nature took before farmers began tilling the soil, according to Howard G. Buffett, whose foundation was the conference’s other co-sponsor.
“Mother Nature does some amazing things that man can’t do,” Buffett said. “Cover crops are a natural step to adopting a broader system.”
Buffett introduced cover crops to his no-till system five years ago on farms near Decatur, Ill., and Omaha, Neb. Improving the system required overcoming mental hurdles. “We do things the same way that Dad did for years,” Buffett said. “Many farmers don’t farm with a system in mind. Until we do that right, we won’t reach the point where we are the best we can be.”
In the past 30 years, 43 million acres of U.S. farmland has been lost to development, said NRCS chief Jason Weller. Of that, 14 million acres are some of the nation’s best agriculture soils. Factoring in increased demand for food, less land on which to grow food, and extreme weather events, and it will be ever more challenging for U.S. farmers to continue to feed the world.
“One of the best tools we have to manage and ensure the long-term vitality of our farms is through soil health management systems and to take the knowledge that producers have and share that information across the landscape,” Weller said.
Soil Health Benefits
Proponents of cover crops believe that when grown in conjunction with cash crops, they can improve soil health. Cover crops help increase water infiltration, water holding capacity and water quality; increase nutrient availability and improve plant health. “It is not just that you have greater diversity of microorganisms in the soil, there is a stronger community, too,” according to Wayne Honeycutt, deputy chief for science and technology with NRCS.
North Dakota farmer Gabe Brown noted that in native pasture near his hometown of Bismarck, there are 140 different species of plants growing. “On our 2,000 acres of cropland, and we have cover crops growing on all of them. Nature has the template; we are merely trying to mimic it.”
Cover crops “harvest” the energy from sunlight, in effect feeding the roots of growing plants. Brown uses cover crops to bring atmospheric nitrogen into the soil. “We use a tremendous amount of legumes, because there are thousands of tons of nitrogen in our soil. We haven’t used any commercial nitrogen fertilizer in five years,” he said. “We want to sign the back of the check, not the front.”
Brown uses the below-ground community to build soil organic matter and microbial activity, which can help reduce the dependence on commercial fertilizers and improve water-holding capacity. Kris Nichols, soil microbiologist at USDA’s Northern Great Plains Research Laboratory in Mandan, N.D., explained that each handful of healthy soil contains billions of organisms, all of which are hungry. A healthy soil ecosystem is the continuous source of food for that community.
“You can add crop residue, manure and other things to the soil, but nothing replaces roots as a source of food for these microorganisms,” Nichols said.
Bacteria and fungi are the most prevalent of the soil microorganisms; these are highly adaptable and are storehouses of nitrogen. They contribute to soil stability and may fix nutrients or release those that are tied up in the soil, she added.
“Soils are a life-sustaining ecosystem,” added Dave White, former chief of the NRCS, “and soil health must be a critical part of the future if we are to meet the challenges that lie ahead. In the next 40 years, farmers will have to produce as much food as they did in the previous 10,000 years, without trashing the environment.”
For example, soils covered by crops can help prevent wind and water erosion and also sequester nutrients that could run off of bare soils. Farmers in Maryland have incorporated cover crops to reduce sediment load in the Chesapeake Bay, which has been overloaded with sediment from urban development, farms and construction in the last three decades.
Adoption of cover crops into a corn/soybean crop rotation can boost yields of the two cash crops, according to surveys conducted by SARE and the Conservation Technology Information Center in 2012-13 and 2013-14. More than 750 farmers completed the survey the first year, and more than 1,500 farmers the second year.
In the drought year of 2012, corn yields following cover crops were 126.2 bushels per acre, compared to 115.1 not following covers. Soybean yields were 47.1 following covers; 42.2 by themselves.
In 2013, corn yields were 168 bushels per acre following cover crops, 160.2 without; soybeans 49.4 with covers, 47.2 without.
SARE’s Myers said the average survey respondent said it took $37 per acre to buy the seed and plant the cover crop, offsetting the yield increase brought on by the use of cover crops.
Many farmers would spray during the idle period to keep weeds at bay; cover crops will help prevent weed proliferation while adding other soil benefits, Myers said.
And, there are other economic benefits besides just yield. A nitrogen credit between 0 and 30 pounds per acre; improved weed and pest management and grazing opportunities of $30 to $45 per acre. Growers responding to the SARE survey report that cover crops often provide deep rooting action that opens up root channels for cash crops. Plus, the residue from a cover crop helps reduce soil moisture lost to evaporation.
“Cover crops begin to pay even in the first year or two,” Myers said.
Indiana farmer Jamie Scott told farmers at the conference that his corn had a 30 to 40 bushels per acre gain following a cover crop of annual ryegrass planted into growing soybeans, compared to corn planted the spring after a soybean crop into bare stubble.
Popular Cover Crops
The beauty of cover crops is that there are a variety of plant species that can help almost any farmer accomplish his or her goals.
The survey of 3,000 farmers conducted by SARE indicated the following species were most popular with farmers. Brief descriptions and examples of selected species follow; more detailed information is available at www.sare.org. Also find the publication “Managing Cover Crops Profitably.”
Winter annual grasses—These species can be planted in fall and will grow after a cash crop is harvested. The thick mat of deep roots make these ideal as a soil builder, subsoiler and erosion preventer. They also have good grazing value. Examples are annual ryegrass, barley and winter rye.
Legumes—Legumes convert atmospheric nitrogen to ammonia. They are a popular cover crop in that they can reduce the amount of commercial fertilizer needed on cash crops. They can be used as a soil builder, erosion preventer and nitrogen scavenger. Examples are soybeans, field/winter peas, cowpeas, alfalfa, crimson/red/sweet clovers and hairy vetch.
Brassicas—Noted for their deep tap root, brassicas can scavenge nutrients and break up soil layers. Some are considered to be “fumigants” and can reduce pressure from nematodes and weeds. Examples are mustard, turnips, radishes, canola and sunflowers.
Summer annual grasses—These are a good choice for planting in the spring as an eco-fallow crop. Most of these can be cut for hay or grazed. They can scavenge nitrogen, prevent establishment of weeds, and have abundant root growth to help feed soil microbes and prevent erosion. Examples are spring oats, Japanese millet, pearl millet and sudangrasses.
Multi-species mix—Combining seeds from the species listed above can provide multiple benefits.
Source: High Plains Journal