Multi-species cover crops help control weeds

Saskatchewan producer finds that as many as five to eight species are needed to meet many of his soil-health goals

Garry Richards says incorporating a cover crop cocktail into his rotation helped him reduce the amount of fertilizer, herbicide, insecticide and fungicide he uses on his farm near Bangor, Sask.

“Rather than reaching for them (chemicals) first, they are way down the line as far as a ways to produce crops,” Richards said after his presentation at the Saskatchewan Soil Conservation Association’s annual meeting in Saskatoon.

A cover crop cocktail is a cover crop that contains many plant species, which he said has helped his mixed cattle and cash crop operation become more profitable.

Growing many plant species in the same field at the same time creates a more diverse polyculture. Each species is added to the cover crop to accomplish a specific job.

“There are tap roots, turnips, radishes, those things will bore down six, seven, eight feet into the soil,” Richards said.

“There are nutrient scavengers, pollinator attractors, nitrogen fixers, carbon providers, and some plants are just there to capture solar energy and help build soil.”

As many as five to eight plant species are needed to achieve many of the soil health goals that Richards sets for his cover crops.

“What is above ground is a mirror image of what is below ground, so if there is lots of diversity above ground, there will be lots of diversity below ground as far as microbiology,” he said.

The crop’s canopy cover is designed to capture as much solar energy as possible.

Roots produce sugar during photosynthesis, which feed micro-organisms. Healthy microbial populations help keep plants healthy and increase their ability to resist diseases, Richards said.

“We don’t want to see any bare soil at all,” he said.

“With monocropping, photosynthesis is really limited. We’re really only photosynthesizing 60 or 70 days of the year. In 2015, we had fields that were green for over 200 days.”

Richards said he has increased soil organic matter and improved soil structure in his fields since he began growing these diverse cover crops, which has enabled more water to absorb into his soil instead of allowing it to run off and contribute to local flooding.

“We want soil aggregates, we want to restructure our soils. We basically want to turn our soil into a sponge that absorbs water and stores it,” he said.

Richards plants his cover crops in the spring and uses both annual and biennial mixtures.

“So we will seed it one spring and it will grow as biennial the next year, and we are even trying to extend that further out with some perennials,” he said.

“So we will get three years of crop with one seeding.”

Richards often harvests the cover crop as silage or green feed and then turns out his cattle on the field to mop up remaining crop residue.

“We got eight metric tonnes per acre, and the cost on that silage was about half of what our cereal silage cost us to produce,” he said.

“We then followed up with a graze once it was all silage off. There was still a ton of stuff growing, adding more value.”

He sprays glyphosate once the cows leave the field and immediately puts it back into cash crop production, sometimes seeding a winter cereal.

He also grows canola in his rotations, usually following the cereal and preceding the cover crop cocktail crop.

Richards said he will spray herbicide when he needs to, but the cover crops and his harvesting methods have reduced weed pressure.

The cover crop canopy out-competes weeds, and the weeds that do grow can often be harvested as feed before they have a chance to seed out.

“Weeds are symptom of a lack of diversity in our monoculture rotation,” he said.

“Now the big thing is weed resistance to herbicides. They’re not resistant to cows and they’re not resistant to iron, so we can silage them and get rid of them that way.”

Richards said the cover crop cocktail works because his livestock operation allows more flexibility in how many acres are allocated to produce feed and forage for the cattle.

Mixed farming operations are more environmentally friendly than those that focus only on cash crops, he added.

He said producers who want to be sustainable should understand and mimic the natural process that nature uses to maintain soil fertility.

“There is no system on the planet that I’m aware of where there is grassland without a grazing animal, whether it was the bison here or wildebeest in Africa,” he said.

“That is the how the system was made to operate, so I don’t think we should deviate too far from it as farmers.”
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