Your Reading List

The cover crop learning curve

There is plenty of good information in theory, but a Taber grower is learning what works best for his farm

Challenges, commitment, trial and error, faith and steep learning curve. Those are some of the terms that southern Alberta farmer Brady Valgardson uses when he describes his experience with regenerative agriculture over the past five years.

Valgardson, who is the fourth generation on the family farm southwest of Taber (about 50 kilometres east of Lethbridge), has some fairly basic objectives as he applies regen ag techniques to the farm that, along with spring wheat and malting barley, produces several specialty crops all under irrigation.

One objective is to reduce the risk of soil being lost to wind erosion during that vulnerable post-harvest/pre-seeding — fall to early spring — period. And he’s hoping in the process of protecting the soil, those practices are also helping to improve soil quality.

Related Articles

At a glance: As part of a regen ag strategy, once the main cash crop has been harvested, a cover crop is seeded to protect soil from wind erosion. Different options exist depending on the crop and growing season conditions.

“Basically, the idea is to keep something growing on the soil at all times right up until freeze-up in the fall,” says Valgardson. “And depending on what I’m using as a cover crop, that crop could keep growing in early spring right up until seeding.

“I have been using some of these practices for several years, but really started to pay attention five years ago. I believe I’m starting to see benefits, but it takes time. We need more research to help answer the questions.”

The Valgardson farm produces sweet corn and green peas sold to local food processors, sunflowers for Spitz (the confection market), spring wheat, malting barley, sugar beets and potatoes. The potatoes are grown in rotation with another farmer as they trade fields back and forth. And some years he also grows some alfalfa.

Valgardson has used tillage radish as a cover crop. It has a taproot that can reach nutrients deeper in the soil. It also helps loosen the soil and brings nutrients back into the root zone of the crop.
photo: Brady Valgardson

“My biggest concern, going back several years, is that once the potatoes were harvested, often on fairly sandy soil, those fields were at risk of wind erosion,” he says. “And with the winds we get in southern Alberta in the fall, and they can be even worse in the spring, as that soil starts blowing it can be a real mess.”

An inexpensive treatment

A simple and fairly cheap fix to protect potato fields was to broadcast wheat or barley seed after harvest in early fall, get it growing and protect the soil right up until freeze-up. At least the soil was protected in the fall.

However, through his own research and working with crop consultant Scott Gillespie of Plants Dig Soil in Taber, Valgardson has been looking at different options for using cover crops across the whole farm, to keep something growing on fields.

(Gillespie is a presenter on Feb. 16 at the virtual 2021 Alberta Nutrient Management Seminar Series running now through February. Visit nutrientmanagementab.ca.)

The concept is once the main cash crop has been harvested, to seed another crop that will quickly germinate and grow right through until freeze-up. That cover crop not only protects the soil from erosion, but being actively growing and in a vegetative state is actually returning carbon to the soil, which supports billions of organisms such as mycorrhizal fungi and microscopic bacteria.

And if those soil organisms are working at optimum strength, they can benefit soil quality in a number of ways, such as increase soil tilth and water infiltration, improve nutrient uptake by plants, and even help crops ward off the effects of insects and diseases.

Timing is critical for establishing any type of cover crop, particularly in the Prairie regions. Seeding something in late September or early October, for example, doesn’t give the cover crop much opportunity to germinate and get growing before freeze-up. The earlier the harvest the better. Unfortunately, sugar beet acres so far haven’t been included in the cover crop program as that crop isn’t often harvested until late October or November, making it too late to get a post-harvest crop growing.

A combination of fall rye and tillage radish has been seeded as a cover crop.
photo: Brady Valgardson

Keeping that in mind, Valgardson has tried different cover crop treatments ranging from what he describes as the “poor man’s cover crop,” to seeding a commercial multispecies blend or his own combination of cover crop species, depending on the crop and growing season conditions.

Different cover crop combinations

The poor man’s cover crop, which works well after cereals are harvested, involves a “light, quick tillage after harvest and putting water to the field to get cereal crop volunteers growing,” says Valgardson. Those volunteers can get well established, putting down roots and producing about five to six inches of above-ground biomass before freeze-up.

On the other end of the scale, Valgardson also uses a multispecies cover crop blend available from a seed retailer that includes fall rye, tillage radish, phacelia (from the borage family), clover and buckwheat.

While the multispecies cover crop is relatively expensive (about $30 per acre for seed), he says it has the best fit following the pea crop. Peas are usually harvested in late July, providing a wide window to get the cover crop seeded and growing.

He’s found there are pros and cons with most of the species used for cover crops, so it’s a matter of trial and error to see what has the best fit. While wheat and barley are fairly cost-effective cereals that can protect the soil in the fall, they’re finished growing with the first killing frost, with little residue left to provide ground cover in early spring when wind and soil erosion can be at its worst.

He has learned fall rye makes excellent ground cover and remains in a vegetative state not just in the fall, but right through until spring. “Any day in the winter if the temperature gets up to about 0 C it starts growing,” he says. And that’s great for protecting the soil.

But the growth and biomass of fall rye can be too much of a good thing, creating a challenge for seeding equipment to work through when it comes to spring seeding. And with the fall rye, he needs to apply glyphosate in the spring to terminate the crop. The timing of the glyphosate treatment has to be early enough so the fall rye doesn’t impact the growth of the new crop to be seeded in the spring.

Fall rye produces a biological phenomenon known as allelopathy, which means it is a crop that produces one or more biochemicals that can inhibit the germination, growth and survival of another crop. The fall rye has to be terminated early enough in the spring to allow the biochemicals to dissipate from the soil.

Valgardson says he has sometimes seeded fall rye on its own and also tillage radish on its own and sometimes a combination of the two. Tillage radish has a taproot that can reach nutrients deeper in the soil. It helps loosen the soil and brings nutrients back into the root zone of the crop.

However, with a tillage radish seeding in the fall of 2020 he did learn to pay attention to surrounding crops and pest conditions.

“The tillage radish was seeded in a field surrounded by canola,” says Valgardson. “It emerged and was growing fine until the flea beetles moved in from the canola crop and there was no tillage radish left at all. I have grown it other years without this problem, so I need to pay attention to where it is seeded and to pest conditions.”

While he has included clover in some of the cover crop seedings, it does emerge “but it really doesn’t do anything in terms of growth, so I don’t believe it is doing much to benefit the soil,” he says.

So, are these cover crops making a difference? On one field where he had seeded a fall rye cover crop, the subsequent corn crop yielded 10 tonnes per acre. On similar land where he had used barley for a cover crop, the corn yielded about six tonnes per acre.

“On one hand, I can think it is the type of cover crop I grew that made a difference in corn yield,” says Valgardson. “But on the other, I have to wonder if the cover crop might have influenced the soil test analysis and based on that perhaps I didn’t apply enough fertilizer. I like to think the cover crops are making a difference, but at the same time there can be so many variables.”

Valgardson says he will continue more trials and experimenting with different cover crop combinations because it does help to reduce the risk of soil erosion and he believes “keeping something growing” benefits soil health.

“Until there is more research providing more answers you really do need to have faith that you’re on the right track with cover crops and regenerative agriculture practices,” he says. “It does take time, extra management and extra cost to try these practices, so you need to be committed to the idea, realizing there may not be any immediate benefit. You’re in it for the longer term.”

About the author

Field Editor

Lee Hart

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

Comments

explore

Stories from our other publications