Good reasons to plant cover crops

If you went to a workshop about cover crops 10 years ago you wouldn’t have had any trouble finding an empty seat. Today, producers pack these workshops. Word is spreading about the benefits that cover crops could bring to their farms.

Cover crops provide many soil and production benefits: increased organic matter content, vibrant, working soil microbiology that gives better nutrient cycling, weed control, improved water holding capacity and infiltration, reduced soil compaction, and more resilience under stress from excess moisture or drought are just a few of them.

Kevin Elmy was one of the few producers who attended those early cover crop workshops and now he gives them — explaining to others how cover crops have helped reduce his financial and environmental risk and make his farm more sustainable.

“By including cover crops on our farm we have reduced our costs, increased our gross, and increased our net dollars without having to put out more money,” says Elmy, owner of Friendly Acres Seed Farm near Saltcoats, Saskatchewan. “Instead of investing in short term inputs like fertilizers and pesticides, we have invested into more seed to improve our soils. If a cover crop blend is $25 per acre, what do you get for that compared to if you are buying fertilizer at 60 cents a pound? At $25 an acre you would get 40 lbs. of nitrogen and you might get a slight response in the crop from that. With $25 in cover crop seed per acre we are building up organic forms of plant nutrients, which will stay in our soil longer. We don’t have to worry about it gassing off or leaching out because it’s in a plant available form. So we are able to build organic matter, recycle nutrients and keep our soil microbes happy.”

The microbiology

To understand cover crops, it’s necessary to know how life functions, above and below the ground. Plants and soil microbiology have a symbiotic relationship. “Plants convert CO², water and sunlight, and produce energy for plant growth. Half the sugar a plant produces is exuded through its roots to feed the soil microbiology, which in exchange converts the minerals the plant needs to grow into a plant available form it can use,” says Manitoba Grazing Club co-ordinator, Michael Thiele, who has been championing the use of cover crops and intensive grazing management, organizing workshops and field tours (with funding assistance from Ducks Unlimited Canada) for many years.

One of the best ways we currently know to keep this symbiotic relationship between plants and soil life in balance is to combine cover crops with livestock, and manage grazing to provide short grazing periods and long recovery periods, says Thiele. Depending on the size of paddock, and the time of the season, producers should move animals frequently enough to make sure they graze only the top third of plant growth, and leave that paddock to rest at least 90 days before returning to graze it again.

“When we clip a plant too short it sloughs off a lot of root system and takes more time to recover,” he says. “If we leave plenty of plant leaf matter it can still collect energy and it doesn’t slough off as much root system. When it produces a flower or seed head, the plant has fully recovered. The focus is on the rest not the grazing.”

Cattle trample the remaining two-thirds of plant growth down to provide “armour” for the soil. “There should be no bare ground,” says Thiele. “When the ground is covered it stays cooler, and a mix of shallow and deep rooted plants help break up hardpan to give better water holding capacity, and provide good water infiltration, preventing erosion. The litter provides organic matter as food for the soil biology, which builds more productive soil over time.”

If there is no soil armour, soil becomes compacted and rainfall will run off because it can’t infiltrate. Conversely, in times of drought, deep roots can scavenge water from deeper in the soil profile. What a well-managed system does, in essence, is build resilience to different weather conditions.

Plant diversity is also crucial. Soil life needs to eat throughout the season, so a cover crop mix of warm and cool season plants ensures they always have food. Ensuring plants are grazing at different times of the year also helps to extend the grazing season in spring and fall.

Benefits without cows

Cover crops give fast results when combined with grazing, but what happens if you don’t have cows? There are a couple of options. You can work collaboratively with other producers who have livestock, or use cover crops as part of a long-term crop rotation to build soil over time.

“I replaced canola in my rotation with a cover crop that my neighbour comes and cuts and bales for green feed for his cattle in August, and then I seed my winter triticale on time into better soils, and a better seed bed with less inputs,” says Elmy. “When we used to grow canola and sow winter triticale or winter wheat into the residue, the ground would be so hard, we would have to wait for rain to get that crop going. With a cover crop the ground is mellow, we can seed through a lot more trash, which allows more soil armour, and the plants come out of the ground significantly quicker, and we seed on time which spreads out my workload.”

Elmy manages annual cash crops, cover crops and perennials to help him maintain the health of his soils, through a well planned, long-term rotation over his 1,500 acres. “If a producer seeds a cover crop blend of annuals and perennials with winter triticale in the fall they trap snow and keep the ground temperature warm so the triticale overwinters well,” he says. “The following spring they can take a cut of green feed and maybe graze the cover crop later in the season. Within three years the perennials take over the stand, which they can still graze and hay for a couple of years before terminating it and growing a cash crop, capturing all the free nutrients they have built up. Then they can go back to a cover crop again. It’s a five or six year rotation.”

Researchers have discovered there are millions of microbes present in soils, and many different types eating different things. A crop rotation of wheat and canola selects for microbes that only feed on those types of material; that reduction in the diversity of soil biology is what allows pathogens, that might have been killed if other types of soil microbes were present, to take hold. Other farming practices, such as high nitrogen fertilizer rates favour diseases such as clubroot and fusarium, which thrive in high nitrate soils. “If we can alternatively produce organic forms of nitrogen and free up and use the biology in the soil to produce plant friendly sources of phosphorous we win,” says Elmy.

Elmy has lowered his fertilizer costs. “On 1,500 acres our fertilizer bill was $60 to $70 an acre on average and now its $10,” he says. “And we have not seen a yield penalty. Our crops are as good as they have ever been.”

Cover crops for 
weed control

Elmy has also used cover crops to get rid of volunteer canola that was showing up in his Roundup Ready soybean crops. “The easiest way to get rid of volunteer canola is to grow a cover crop. When it’s almost at full flower I go out and cut it for green feed and there goes my weed issue,” he says. “I am decreasing the seed bank using other methods, besides chemicals, to bring the weed bank down.”

Cover crops provide ground cover for low residue crops like flax, soybeans, lentils and peas, helping to retain moisture and prevent soil erosion. Elmy has also found tillage radish to be a great weed suppressant. Seeded the first part of July, the tillage radish’s large leaves touch the soil surface when they mature and begin to rot, give off an organic acid that kills anything underneath them. Elmy direct-seeds winter cereals into the rotting leaves in the fall using a seeding shank or knife to move the soils and leaves away, and the seeds come up no problem, while the weeds in between the seed rows, under the rotting leaves, don’t grow and compete with the emerging crop.

Elmy says just understanding soil and plant biology gives producers more options to experiment with different crops and different markets. “They have options. If it turns dry they can take a graze off their cover crop and then rest their pasture to allow it to re-grow and have the option to put the cattle back in later or take it as a cut, or leave it as insurance,” says Elmy.

“On the corn crop that I am grazing right now, I am going to sow that down to orchard grass afterwards and hay it off to try and go for the horse hay market because my NPK are all high. If it turns rainy and I can’t make the grade for the horse hay market, the cows will eat crested wheat grass and I can still have some cash income and am still managing my nitrogen.”

How to know if your soil is healthy

1. Look for earthworms. When you dig six inches into the soil, ideally you should have at least five earthworms in that sample. These amazing “soil engineers” are the foragers that bring litter and plant matter down into the ground to be broken down into plant useable nutrients by soil biology.

2. Look for dung Frisbees. If the cow patties in your field are so hard you could play Frisbee with them it means that the soil biology isn’t getting what it needs to break them down. Dung should disappear within a few days when healthy soil biology is working as it should.

3. Poke in the poop. If you break apart some fresh dung and find lots of beetles inside, then you know that you are creating a healthy soil environment that will break down and use the manure to make your soils more productive.

4. Insert a knife. How far can you easily push a knife — or you can also use a tool called a penetrometer — into the soil before you encounter resistance? That’s the depth of hardpan or compacted layers. In good, healthy soil your knife blade shouldn’t reach any hard soil.

This article was originally published in Grainews magazine.