Hairy vetch may be the key to reducing tillage in organic farming, at least in the short term.
Martin Entz, a professor and agriculture systems expert from the University of Manitoba has been looking at mulches for organic weed suppression, rather than the tillage typically used.
“We found that when we used the right mulch, or the right mulch combination, that the organic no-till system performed very well,” he said.
Entz combined hairy vetch with barley as a green manure mix in a 6-year rotation, starting with pea-oat green manure, followed by spring wheat, soybeans, the barley-vetch mix, flax and ending with oats.
Adapting methods from Brazil, Entz blade rolled the barley-vetch mix once the barley flowered, crimping the cereal and creating a mat through which vetch continued to grow until freezing.
“That year that we grow the hairy vetch as a green manure, the following year we are able to no-till that crop,” Entz said.
“We can no-till flax into there. We can no-till wheat into there, and that works quite well. Basically, we’ve eliminated tillage in 1 out of 6 years, and we’ve tried to push that system further to look at whether we can eliminate tillage for 4 or 5 years. We grew a hairy vetch cover crop and then we just kept no tilling crops into there, and that sort of collapsed after 2 years. We got 2 no-till crops after the hairy vetch, and after that the weeds just overran the plots. That’s the capacity of that system.”
The legume has proven to be the most effective element in Entz’s green manure mulches when applied at a high seeding rate.
Field experiments from 2010-12 found wheat yields in organic no-till were comparable to regional averages for between 1-1/2 to 2 years following a vetch or vetch-mix mulch.
The research compared 10 cover crop combinations, including barley, pea, vetch, radish and sunflower. Results showed only pure vetch and the barley-vetch mix produced less than 0.44 tons per acre of weed biomass.
Wheat seeded into vetch mulches also yielded the highest out of the no-till plots and, along with pure pea mulches, had the highest uptake of nitrogen, ranging from 85 to 90 pounds per acre.
The study noted however, that pure vetch was slower to emerge and was less competitive with weeds during the green manure year.
Likewise, Entz added, mulches have not proven effective against wild oats and are best used against broadleaf weeds.
The barley-vetch combination has since been integrated in long-term organic plots at the Bruce D. Campbell Farm and Food Discovery Centre in Glenlea.
“Producers are starting to work with hairy vetch, there’s no question about that,” Entz said. “It’s got other attributes, like it’s a very good nitrogen-fixing plant. It really is quite a bit better than most of the legumes that we have.
“So producers are in that early-adoption phase and they’re experimenting on their own farms with what kind of seeding rates they’re prepared to pay for. That’s one of the challenges with this plant. You need about 25 pounds per acre of seed to really get a good stand, a good dense mulch and the seed is about $2-$3 per pound.”