Best to start small when adopting cover crops

Herbicides aren’t effective because of the variety of crops, but farmers are finding that heavy seeding rates can help control weeds

ROCKY MOUNTAIN HOUSE, Alta. — Growing a balanced mixture of plants in a cover crop is a new concept and farmers are still learning how it builds soil.

Like any new idea, it is a good idea to start small, said Greg Paranich, agriculture fieldman with the Grey Wooded Forage Association.

“You can calibrate what works best for you,” he said during a field day in Clearwater County in west-central Alberta.

The county is testing varieties and mixes to learn what works in an area with a short growing season, higher elevation and variable soil types.

He recommends picking three to four species to see what grows best. A balance of 20 percent brassicas, 30 percent legumes and 50 percent grass offers benefits to the underground community of microbes, as well as provides a good mix of forages.

The county has tried different plants, adding smaller mixtures of clover and brassicas like turnips and radishes to barley planted at various seeding rates.

Kale has also been part of the experiment.

Greg Paranich of the Grey Wooded Forage Association shows the long roots of tillage radish that are used to break up compacted soil in a cover crop mixture. | Barbara Duckworth photo

Brassicas have big deep roots and can reduce soil compaction, he said. The tubers break down in the fall and disintegrate quickly to distribute nutrients. They don’t provide much forage but are good for the soil if they are not planted at a heavy rate. They draw a lot of nitrogen and sulfur from the soil.

The association has also tried sowing Italian rye grass. It is a soft, shiny grass and the cattle like to eat it. It is nutritious and leaves a mass of roots for organic build-up and fibre in the soil.

Crimson clover was added to the mix. It is a low-bloat legume that can fix nitrogen in the soil.

The end goal is to grow additional forage in a green feed or silage stand, as well as offer late-fall or early-winter grazing. They also want to keep the plants alive for as long as possible.

“Try to have as long a period of living roots in the soil as possible. These roots feed the microbes,” Paranich said.

Agronomically, some management changes may be needed, said Devin Knopp of Benalta Agri Services.

Heavy seeding rates of these mixture crops offer better weed control.

“There is no herbicide option that is not going to eliminate something that is in there,” he said.

“You need to use these as a natural control agent. Don’t cheap out and try and save a bit of money on a few pounds here and there. It is better to err on the side of heavier rates.”

Producers need to add fertilizer to give these crops a head start because in some regions, the growing season may be too short.

The mixtures also offer a good mix of deep and shallow roots for soil building.

“Some people say it takes hundreds of years to rebuild organic matter. I would argue it takes a decade and you can rebuild organic matter by a percentage or two just by using these mixes and grazing and other facets to improve your soil,” he said.

Soil testing is needed to assess improvements and the producer should do it himself to learn what is happening on his land, said Knopp.

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