The health of your soil can spell the difference between bumper crops and major flops. And while that’s not a revolutionary idea, more and more farmers today are looking for natural ways to supercharge their soil health. In the process, they’re reducing input costs, suppressing disease, boosting yields and revving up climate resilience.
Compost Council of Canada’s Glenn Munroe.
According to the Compost Council of Canada’s Glenn Munroe, the secret lies in rolling out the welcome mat for as many beneficial fungi, microbes, nematodes and other life forms as possible — and then letting them do their thing. “You can’t really talk about soil health unless you talk about the organisms,” he says.
Over the past ten years, researchers have unearthed oodles of important discoveries around how the creepy-crawlies living in the dirt make a difference and what farmers can do to squeeze the most benefit from them. We shed light on some of the latest — and coolest — scientific insights into soil health.
Noshing nematodes
Watch a yogurt commercial and you’ll likely hear the announcer tout the virtues of probiotics: healthy bacteria that improve gut health by helping us break down food and absorb nutrients. Plants use microbes in similar ways.
Fungi are good at breaking down minerals and organic matter in soil, absorbing the nutrients into their bodies.
Bacteria and fungi are good at breaking down minerals and organic matter in soil, absorbing the nutrients into their bodies. Hungry microscopic nematodes then eat the bacteria and fungi and release excess amino acids, ammonium, phosphate and other nutrients as a sort of microbial manure that plants can absorb more easily.
“There’s a whole system set up down there to recycle nutrients, to extract them from the minerals and to deliver them in a timely fashion to plants,” Munroe explains.
In 2016, researchers from Belgium set out to quantify those benefits, revealing that the presence of nematodes in soil boosted the available nitrogen and phosphorous by 25 and 23 per cent respectively and enhanced overall plant growth by nine per cent.
Delivering the goods
Similarly, mycorrhizal fungi offer important food delivery services, connecting with plant roots and providing nutrients in exchange for sugars and other carbon compounds. Their tendril-like “hyphae” can also dig deeper and farther, expanding a plant’s feeding area. (For more information about mycorrhizal fungi, check out the Research Notes in our January/February 2018 issue.)
Meanwhile, research shows that a healthy network of these fungi can be your field’s best friend when the rains refuse to fall. Using florescent dyes, American and Spanish biologists tracked the movement of water through a fungal network and into the roots of drought-stressed seedlings. Their conclusion? Mycorrhizal fungi increase drought tolerance by delivering water when plants need it most.
Fungi also help the right amount of water and air to reach plant roots by improving soil structure, wrapping their hyphae around smaller bits of soil to form larger clumps. In addition, fungi, bacteria and earthworms secrete organic glues that hold particles together, helping create a stable, well-formed structure that reduces runoff, prevents erosion and holds water better.
Rallying the troops
In true symbiotic fashion, it’s in the best interest of soil-dwelling organisms to protect the plants they rely on for survival. Indeed, the beneficial dirt-dwellers in your fields act like white blood cells in the human body, attacking unwelcome guests. And over millennia, Mother Nature has designed some pretty clever defence tactics.
Take the bacteria Bacillus subtilis. In 2012, scientists from the University of Delaware investigated the contributions of this surprising crop ally. Some pathogens use the microscopic pores on a plant’s stems and petals as a way to sneak inside. However, the researchers found that if Bacillus subtilis is present in the soil, it can send a signal to the plant, telling it to close its pores to ward off infection.
Meanwhile, mycorrhizal fungi can serve as a sophisticated alarm system for tomato plants. When attacked by leaf blight, tomato plants will activate defence genes that help prevent infection. But studies showed that nearby tomato plants that haven’t been infected yet also activate those defences. How do they know to do that? In 2010, Chinese researchers discovered the plants were sending advanced warnings to their neighbours through their roots, using the fungi that ran between them as an underground communication conduit to deliver messages.
In 2013, researchers found similar mechanisms at work with fava beans. When attacked by aphids, the bean plant will begin emitting a chemical that attracts wasps that come and eat the invaders. However, like the tomatoes, neighbouring beanstalks will also start producing the chemical. Sure enough, the investigators found that the plants were using fungal networks to alert their fellow beans.
Promoting soil health success
The Compost Council of Canada has been running workshops across the country to help farmers boost their microscopic soil “livestock.” Munroe is quick to point out that his organization isn’t promoting a particular approach to agriculture. He believes that any farmer — organic, conventional, big, small — can benefit from finding ways to enhance soil health. “Our focus is on helping them to get the most they can out of the natural system,” he says.
To that end, the Council has identified five core principles — principles that will sound very familiar to organic practitioners and are gaining more and more traction within conventional agriculture as well.
1. Disturb the soil as little as possible. A big advantage to no-till farming is that it allows the underground ecosystem to grow and thrive, leaving soil structure and beneficial fungal networks intact. “Every time you do some kind of major event in the field,” says Munroe, “you’re knocking the whole system back ecologically to a simpler, earlier system, and then it has to build its way back again.”
2. Cover the soil. Cover crops protect the soil and reduce erosion, ensuring your beneficial microorganisms don’t get washed away.
173005830
Leaving as many live roots as possible in the ground — even during winter — helps keep your nutrient-delivering, drought-busting fungi alive and ready for action next season.
3. Keep live roots in the ground. On a related note, don’t let your fungal networks starve! Leaving as many live roots as possible in the ground — even during winter — helps keep your nutrient-delivering, drought-busting fungi alive and ready for action next season. “They will be back in strength again in the spring much faster,” Munroe says.
3. Maximize diversity. Using complex crop rotations and multispecies crop covers helps attract a wider variety of beneficial organisms — below the soil as well as above. That biodiversity translates to better pest management, improved soil structure and greater resilience.
4. Add amendments whenever possible. In addition to feeding your beneficial organisms, manure and compost help pull carbon out of the atmosphere, increase soil organic matter and help build resistance to changes in climate.
For information on no-till techniques, how to add more fungi to your soil, which cover crops to use and other specific advice, contact your provincial Ministry of Agriculture. Plus, check out the Compost Council’s website (compost.org/English/soils_at_work.html) for upcoming workshops, resources and quizzes to test your soil savvy.
The deeper you dig, the more you’ll appreciate the importance of soil health. “It makes a difference in how you see the earth beneath your feet as you’re walking in your field,” says Munroe. “There’s a community down there. There’s networks. There’s transportation routes. It’s a whole society.”
- Josh Martin