Earthworms and a teeming community of bacteria, fungi, mites and nematodes are working as hard below ground as farmers do above ground.
A field’s nutrient levels and ability to produce high-yield crops are determined by the health of these microscopic creatures that inhabit the rhizosphere, the top 20-30 centimetres of soil, said Jill Clapperton of the Rhizosphere Ecology Group at Agriculture Canada’s Lethbridge research centre.
If this soil community is encouraged to grow by avoiding tillage and using the right crop rotations, it can greatly reduce the need to apply commercial fertilizer.
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But beyond the immediate considerations of yield and input costs, Clapperton said a healthy soil leads to healthier people.
“If we can use soil biological fertility and increase the nutrient uptake in that grain, we can have higher quality grain and food quality not only for ourselves, but for our animals.”
Clapperton was speaking at the Saskatchewan Soil Conservation Association annual meeting. She said some farmers are wary of getting into zero-till management because they don’t know how they’ll be able to manage crop residue.
But a healthy soil community that includes earthworms will help handle the residue problem, she said.
“They are pulling the residue from the surface and bringing them down so they can decompose more quickly.”
She showed a photo of two flower pots with cereal straw litter on the surface.
One of the pots had two earthworms. In six weeks the worms removed most of the litter.
“Earthworms alone will add anywhere between 15 and 30 pounds of nitrogen per acre, just through their activities. They are decomposing that residue and also because they are leaving their castings and dung in the soil.”
The castings help bind and stabilize smaller soil particles into larger aggregates, improving soil structure.
She said research has shown that the lining of an earthworm burrow is an ideal environment for nitrifying bacteria that convert ammonia to nitrates that can be used by plants. It is no wonder plants often send their roots down earthworm channels, she said.
Earthworms prefer to eat plant material that has been colonized by fungi and bacteria, and this can lead to less fungal disease in crops.
Earthworms don’t have to be added to a field. They will grow and multiply rapidly under zero-till management because the soil environment is not disrupted. Following a diverse crop rotation including forages also helps.
“If you build it, the earthworms will come.”
Clapperton has also found that the worms do particularly well after a canola crop because of the protein in the residue.
“They like high protein food. Earthworms might only have one neuron for a brain (but) they know what is good for them.”
She said if a field must be tilled, it is better to till in the spring, at least from an earthworm’s perspective.
“Fall tillage is the most detrimental thing you can do to soil fauna,” although it is not known why, she said.
Earthworms sit atop the food chain in the root zone and their health is an indicator of the health of all the bacteria, fungi, mites and other soil organisms.
The organisms with the most intimate relationship linking soil and plants are mycorrhizal fungi.
Mycorrhiza penetrate the cells of roots without harming the plant. They send out their own microscopic root-like threads called hyphae that move nutrients and water from the soil to the plant. They are particularly efficient at helping plants take up mineral nutrients and help make grain produced by the plant more nutritious.
“If we reduce the amount of phosphorus we apply, and take advantage of the mycorrhiza, our grain is significantly increased in phosphorus, calcium, zinc and copper and the micronutrients. It is better for you. Eventually, that could be a marketing tool.”
They are important in the early establishment and growth of flax, sunflower, corn, peas, beans and other legumes.
