Title: Cover crops and no-till solutions for weed control
[Winnipeg Free Press 17 Sept 2011 by Laura Rance] -- As PhD student Caroline Halde held up the thick mat of rotting vegetation, it was at first tough to fathom why this would be considered an exciting scientific find. Halde is studying organic-no-till cropping systems at the University of Manitoba's Ian N. Morrison Research Farm near Carman. She's looking for ways in which farmers can pursue organic crop production without having to do so much tillage. Long thought to be at the opposite ends of the spectrum, both conventional and organic systems offer benefits to farmers and the environment, but both are flawed. One depends on destructive tillage as the chief means of weed control. The other depends on herbicides, which face increased resistance in the weed populations.Until recently, marrying the two seemed unlikely. But then researchers started exploring the use of cover crops and mulches. Cover crops have traditionally been used by organic farmers to produce fertilizer. A legume crop, which produces its own nitrogen, such as clover, is planted in the field every second year or so and then worked into the soil, where it decomposes and feeds the following year's crop.
As it turns out, some of these cover crops, particularly a legume called hairy vetch, are also good at controlling weeds. The viny, creeping plant with pretty purple flowers literally climbs the weeds, pulls them down and smothers them as it competes for sunlight. It also produces a lot of nitrogen. All it needs is sun and soil. Even if it is rolled and left on top of the soil, instead of being worked in with tillage, it forms a thick nutritious mulch into which an annual crop can be directly seeded.
Organic wheat sown into plots that grew hairy vetch the previous season is noticeably free of weeds in Halde's replicated trials. Organic flax sown into hairy vetch mulch in 2009 yielded 33 bushels per acre. In 2010, it yielded 24 -- respectable yield's by any farmer's measure.
This work is in its infancy. But these strategies could provide a tool for conventional farmers, too. Even if there is only one year in a farmer's rotation that doesn't require herbicides or nitrogen inputs, this could be an important resistance-management tool, and a money saver. It's main drawback is that there is no annual crop produced in the year the field is producing green manure -- unless it is being grazed by livestock.
Farmers and researchers in other parts of the world are studying these techniques. Some see it as a way for farmers to be more competitive in export markets. Others see it as a way to achieve food security by making their home farmers more productive. Halde has been invited to speak about her work in Korea later this year.
Ohio State University has recently coined the acronym "ECO Farming" to highlight efforts to reduce tillage through the use of cover crops.
"ECO Farming stands for 'Eternal no-till, Continuous living cover, and Other best management practices,'" says Jim Hoorman, extension cover crops specialist said in a release.
"Continuous living cover means farmers try to keep a living crop on the soil 100 per cent of the time," Ray Archuleta of the Natural Resources Conservation Service said. "The goal is to protect the soil from soil erosion, increase water infiltration, and decrease nutrient runoff."
Examples include grain crops followed by cover crops, pasture or hay systems, or perennial plants.
Ohio No-till Council president Dave Brandt has been practicing the concept on his farm for 15 years and said he has reduced his fertilizer inputs by 50 to 70 per cent and herbicide costs by 50 per cent. He also has reduced his fuel consumption. In the process, he has added soil organic matter, which has improved soil health and increased crop yields.
"For 100 to 200 years, farmers have been tilling the soil and basically mining it of nutrients, destroying soil structure and losing 60 to 80 per cent of soil organic matter," Archuleta said.
"Now we can use advanced knowledge of soils, soil health and soil ecology to work with Mother Nature rather than against her."
Granted, a plant named hairy vetch doesn't have the wow factor of some of the test-tube technology in plant genetics hitting the market these days. It is unlikely to replace conventional systems in the near future. But you would think, given their production costs, farmers here would be all over a strategy that offers them weed control and free fertilizer. So far, they seem remarkably disinterested. Thankfully, a small corps of researchers are -- and they are preparing for the day when the rest of us might be, too.
