Cover crop buffet feeds microbes

Peace farmer Bill Gaugler is adding a cover crop to his farm’s 
rotation, in hopes of increasing yields with less fertilizer

Bill Gaugler hopes including a multi-species plant cover crop year in his rotation will improve soil health on his Alberta Peace River region farm. That could lead to several benefits — Gaugler hopes it could help improve his overall crop yields, or allow him to maintain yields with less or even no fertilizer.

It isn’t a far-fetched plan. Some producers in North America have reported great success with cover crop rotations. But Gaugler, who farms near Manning in the north central Peace region admits it took time to get his head around the notion that seeding a cocktail blend of annual grasses and legumes one year can have longer term crop production value.

“I have probably been thinking about this and doing some research over the past seven or eight years,” says Gaugler, who produces wheat, peas, canola, and oats at Hotchkiss, just north of Manning, Alta. “In 2012 I actually tried a 15 acre plot of just peas and oats cover crop, and in 2013 there was a 30 bushel yield increase in wheat just over that plot compared to the rest of the field. That told me something was working.” Gaugler plans to expand that to about an 80-acre trial in 2014.

Cover crop blend

That 2012 experience was followed by a workshop late last year organized by the North Peace Applied Research Association (NPARA), which featured speaker Gabe Brown of Bismarck, North Dakota. Brown, who has spoken several times in Canada, has long included a cover crop on his mixed farming operation. Including a blend of at least 10 cool and warm season crops in a cover crop-year has dramatically improved over all soil health, he says. Brown has not only been able to reduce fertilizer for crops, but most years is able to eliminate added fertilizer completely — the soil has become that productive.

Farmer standing in a field.

Bill Gaugler hopes including a multi-species plant cover crop-year in his rotation will improve soil health on his Alberta Peace River region farm.
photo: Lee Hart

The cover crop Gaugler is talking about is different than a traditional cover crop concept such as seeding a new forage crop, for example, but including oats or barley at the same time so you can harvest something in the year the forage is getting established.

Gaugler’s plan for a cover crop-year is sometimes described as a green manure year. But often a conventional green manure crop is some type of straight legume.

Based on Gaugler’s own research and Gabe Brown’s experience, this newer cover crop idea involves a wide-ranging blend of warm and cool season grasses and broadleaf crops. Brown advocates having at least 10 different crops in the blend to provide a “cap” — a crop biomass that protects the soil, while the diversity of crop roots provide a food source for an enormous number of micro-organisms in the soil.

Using this wide blend of crops makes sense to Newton Lupwayi, an Agriculture and Agri-Food Canada research scientist in Lethbridge, Alta.

“The more diversity of the cover crop, the better it is for soil micro-organisms,” says Lupwayi. “A standard grain and oilseed rotation is good, but it is like giving the soil micro-organisms a meat and potatoes diet. If you increase the crop biodiversity it is like giving them a seven- or eight-course meal.”

And there are a lot of mouths there for crop roots to feed. Lupwayi says there are more micro-organisms in a tablespoon of soil than there are humans on the planet. While improving yield is important and perhaps the ultimate goal, he says cover crops and green manure improve soil organic matter, can add nitrogen to the soil, help conserve soil and moisture and can also improve weed control. These can all contribute to higher yields and improved profitability.

And it is all in the diversity of plants, says Jill Clapperton, a former Agriculture and Agri-Food Canada researcher who now runs Earthspirit Consulting service in Montana.

A diversity of roots in the soil can stimulate and accumulate different nutrients, which in turn supports different micro-organisms in the soil. When those plants die, the roots break down providing more plant available (organic form) nutrients for the subsequent crops. Buckwheat, for example, accumulates calcium and magnesium, lupines affect phosphorus and pulse crops can contribute to nitrogen.

“It is what is known as the rhizophere process,” says Clapperton, the rhizophere being the narrow region of the soil directly influence by root secretions and soil micro-organisms.

“Depending on the mix of the cover crop species we observed at studies done at Lethbridge, crops grown after the cover crops had more nutrient dense grain — wheat for example would have more phosphorous, more nitrogen, more iron or more of some other micronutrients and it all related to the diversity of the preceding cover crops.”

The process, she says, makes more and different nutrients available to the crop, it changes the physical structure of the soil, improves the aggregate stability of the soil, opens the soil deeper allowing plant roots to capture nutrients further down in the soil profile.

“Farmers think about an above ground crop canopy, well this is thinking about a below ground canopy,” says Clapperton. “With a diverse cover crop all roots are crossing over below the soil surface touching each other and they are sharing things. If the crop combination is compatible they are sharing nutrients and water. That is probably why a mixed species stand survives and does so much better than a single species stand.”

She says a cover crop should contain at least three different plant species — more is better. If in field history, plant stands have been heavy to grasses, then add broadleaf species, and if it has been heavy to broadleaf crop, then add grasses.

Clapperton says it isn’t unreasonable to expect as cover crops become common in rotations, to reach a point where little or no added fertilizer is needed.

What to grow?

Back on Bill Gaugler’s farm, he’s thinking about what crops to include in the cover crop mix, and about managing residue the following seeding season. Gaugler, who is current president of the NPARA, takes comfort he is not alone in this learning process. About 10 other Peace Region farmers are also interested in adding cover crops to their rotations.

“We’re an informal group but we’re all starting at about the same point,” he says. “Most are mixed-farming operations, so the cover crop-year may be valuable as pasture for livestock as well. The nice thing about it is that we can learn what’s working from one another, and perhaps more importantly learn from each other’s mistakes.”

Gaugler sees the cover crop as being Year 1 in his rotation. He’ll probably follow the cover crop with canola, which has high nutrient requirements and then move into a spring wheat, or perhaps winter wheat, then peas the fourth year and then back into the cover crop-year. The recommendation is for a cover crop mix of warm and cool season grasses and broadleaf crops.

Among the options for warm season grasses are crops such as sorghum, millet and corn. Warm season broadleaf crops could include soybeans, cowpeas and annual alfalfa. On the cool season side, grasses could include traditional crops such as oats, barley or wheat. Broadleaf crops could include peas, faba beans, chickling vetch and hairy vetch. These are some of the options.

“It would be nice if we can get 10 different crops that all work in this area,” says Gaugler. “But if we only get six that is still better than just one or two.”

Gaugler’s other challenge is to find a seeding system that can work through the cover crop residue the following spring. A long-time direct seeding farmer, he wants something that will cause little soil disturbance.

While he is using a hoe-type air seeding system now, he is looking at moving to a coulter style vertical tillage tool. While it’s not the only option, he is looking at modifying a Salford vertical tillage tool equipped to either broadcast apply seed ahead of the coulters or place seed in the opening just behind the coulters.

“We’ll start out on a trial basis with about 80 acres this coming year,” he says. “It is not like we can jump in and do the whole farm all at once because you still have to be producing a crop. But, we’ll start with some cover crop blends and see what works.”

About the author

Field Editor

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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