There has been lots of excitement during the last few years over cover crops. The soil conferences and seminars have been full of cover crop talks and trade shows are full of salesmen. It is the latest craze in agriculture and I agree that there are a lot of situations where the cover crop is a useful tool. But it is just a tool, not a magic bullet.
What is a cover crop? I would agree that it is a crop grown for the protection and enrichment of the soil. Most cover crops end up being a variety of different plants seeded all at once. I agree with the idea of a cover crop 100 per cent. The soil needs a polyculture of plants in order to give it a polyculture of root systems which can sustain a polyculture of soil organisms. That will go a long way in improving soil health.
Our agricultural soils do not have a fertility issue, they have a biological issue. We need that polyculture of soil organisms.
When planning a cover crop, we look to fix certain issues in the soil by planting a variety of plants to help improve the soil health. We might choose one type of plant over another to address a specific concern we have with the soil. For example, if it lacks nitrogen we will want to add a legume or two to increase the N availability.
What am I looking for in a cover crop? Here are my four points to ponder:
1. I am looking for plants that are fast growing, so they can quickly cover bare ground to protect it. I want roots that hold soil together and keep it from eroding away in the wind or rain.
2. I want plants that accumulate vital nutrients from the subsoil and bring those nutrients into their leaves. As these plants recycle, they release nutrients back into the topsoil.
4. I want plants that are quick to flower in order to attract beneficial insects.
Would you agree with me that these could all be benefits to your soil provided by a cover crop?
Let’s put this into perspective. What I just described to you was nature’s cover crop. Most people refer to them as “weeds.” I call them pioneer species that come in when conditions are harsh and heal the land. They act like a scar that is a part of the process in healing the soil. That is what we are doing with today’s latest trend of planting cover crops. We are planting species that heal the land. I would say that most producers do not have a “weed” issue on their land, they have a soil issue and that soil issue is biological.
So here are a few of my recommendations for a great cover crop that can heal your soil.
Canada thistle is a great soil amendment. It has a huge root that can penetrate deep into the sub-soil through almost any soil type. Its ability to break up hardpan in areas of heavy clay make it a great addition to heal the soil. It is very good at its job. The thistle family is also high in potassium so after the plant dies, potassium, along with many other nutrients that were deep in the soil, are now available at the surface for other plants. You’ll also likely find ladybugs hiding in the leaves. Many beneficial insects are attracted to the polyculture of plants.
If you don’t like thistle, try sweet clover.
Sweet clover was a weed in the ditch back home in Saskatchewan where I grew up. It is a very important species in nature’s cover crop. It has similar traits to Canada thistle with its big taproot to open up the soil. It also has those sweet-smelling flowers that attract beneficial insects. As a bonus, this plant is also nitrogen fixing. It has a symbiotic relationship with a bacteria that provides N to the plant in return for sugar. Every living thing in the soil loves sugar.
Stinging nettle has a long list of human health-related benefits and if you have ever heard me speak, you might know that we harvest it on our ranch. It makes a very healthy and flavourful tea or can be a multivitamin when added to food like a spice. But let’s ignore the health benefits for now.
It also aids the soil by stimulating humus formation and increasing the nutrient density of other nearby plants. It has also been found to help plants nearby to be more resistant to fungus and disease. But be weary of touching it, it holds true to its name.
How about dandelion? Not only is it very nutritious for your livestock, this high-protein plant is also very good at stimulating humus formation, and its root system is a favourite hangout for earthworms. With its deep taproot, dandelions help move minerals, especially calcium, from far below the surface up to the topsoil. It also blooms very early which invites pollinators and other beneficial insects to the party.
White clover is also another plant often found in nature’s cover crop. All clovers have the ability to provide nitrogen in the soil by way of its roots and friendly neighbourhood bacteria. We quite often hear people complain about this “weed” in their lawn but it also attracts beneficial insects and pollinators. Clover accumulates phosphorus for us, attracts ladybugs, minute pirate bugs, and pollinators in addition to providing shelter for parasitoid wasps, spiders, and ground beetles. Clover is a preferred egg-laying site for lacewings. Let the party begin.
Now I will be pushing your limit for “weeds” with this one. Everyone hates burdock but it is a very beneficial plant for us nutritionally because of its high mineral content. It’s also a wonderful soil amendment the way it retrieves those minerals. Burdock has a long taproot capable of busting up hardpan on its way to bring up minerals that have washed down into the subsoil. Just knock it to the ground before it goes to seed. High animal impact can go a long way toward doing that.
Broadleaf plantain is good at healing compacted soil and accumulates calcium, sulphur, magnesium, manganese and iron. When the plant dies, these nutrients become available to the plants and the soil organisms at the soil surface.
Chickweed likes to show up in disturbed soil as well. It is an indicator of low fertility and likes to accumulate potassium and phosphorus. It also attracts soil organisms and pollinators in the spring and early summer.
Lamb’s quarters has deep roots that accumulate nitrogen, phosphorus, potassium, calcium, and manganese while loosening the soil. It will benefit the soil if left to grow and die but one plant can set over 75,000 seeds so you might want to trample them to the soil before they set seed, but leave the roots intact as they will decay, enriching the soil and attracting beneficial soil organisms.
They say tansy is poisonous to livestock but I have never had an incident on my ranch. It is a great plant for wind protection, catching snow and wildlife habitat. I have seen a bird’s nest nestled into the protective base more than once. It is known to help with internal parasites and is a natural insect repellent so its odour helps your livestock with external parasite control. It is known to help protect neighbouring plants from pests and other detrimental insects. It also holds onto potassium.
Do you get my point yet? A cover crop is a polyculture of plants that are trying to heal the land. Nature has been trying to plant cover crops for years but we have been fighting against it all the way. Now it is a new thing? It has always been nature’s way of healing the land.
If you want to heal your soil, the best cover crop is a well-managed polyculture of perennial plants. Note the words well managed. Livestock and good grazing are key parts of this management. Do you want to heal your soil? Do you want to increase your carbon sequestration? Keep your soil covered. A permanent polyculture cover is the best way.
Don’t get me wrong. Today’s cover crops are a great step forward in the grain industry. If you are integrating cover crops and livestock into your grain rotation, good on you. That is a great step forward in soil health, but I would never tear up a forage crop to replace it with a cover crop. Never. We need to sequester carbon into the soil, not release it. A cover crop can not compete with the soil improvement from a well-managed perennial forage.
What is the next step? I am excited about a new type of plant on the horizon. Perennial grain crops could revolutionize the grain industry. We are trying to get seed right now for a perennial wheat (Kernza) for our research trials. I would love to see a perennial wheat crop seeded down with an under-story of perennial plants including legumes and creeping grasses.
Once it was seeded, you would not need to till, spray or fertilize. You would harvest it once and then turn the livestock out to graze the rest. Seed yield production might not be as high, but combined with the second crop of grazing and the reduction of input costs, profit potential could be a lot higher, not to mention the economic and environmental benefits to the lack of inputs required.
That is such an exciting concept for agriculture and for our environment. In my opinion, one step better than a cover crop.