Conventional agriculture’s overwhelming focus on chemistry is fundamentally flawed, according to Matthew George, a lab director with Soil Foodweb Canada.
By neglecting the important role played by soil biology, chemically dependent farming tries to supply the entire scope of a plant’s nutrient needs through artificial means, effectively bypassing natural processes.
The result, he said, is unhealthy crops with poor nutritive value that need to be propped up with pesticides and ever-increasing fertilizer inputs, the cost of which eventually cripples farm profitability.
“We want to correct problems and causes, not just react to a symptom,” said George at a Brandon workshop hosted by Ducks Unlimited Canada and the Manitoba Forage Council.
Drawing from research by plant scientist Elaine Ingram, who has stirred controversy with her alternative views on soil fertility and the role of corporations in industrial agriculture, George says that with a few simple tools and a better understanding of soil biology, farmers can inoculate and restore the soil ecology of their land using “tea” from compost that is rich in bacteria, fungi and other microscopic organisms.
But first, the farmer must understand soil biology.
“You can take a pile of rocks and crush them into dust and send that off to a lab where they’ll tell you that you have potassium, magnesium and calcium and whatever else. But you can’t grow anything in it. That’s because it’s the micro-organisms in the soil that power and cycle its fertility. It’s soil biology that makes the minerals and chemicals available to the plant,” he said.
“There’s an army of good guys and an army of bad guys. They are always fighting and competing with each other.”
The “good guys” are the soil flora that like to live in the presence of air, or the aerobic zone, which is the top few inches of topsoil.
The “bad guys” tend to live farther down, in the compacted anaerobic zone, where less air spaces are present. Without oxygen, they make a living by fermenting soil organic matter, and produce toxic alcohols and formaldehydes that plant roots avoid.
Aerobic organisms, such as arbuscular mycorrhizal fungi, on the other hand, thrive in the oxygen-rich environment of non-compacted soils. In exchange for sugars, carbohydrates and proteins supplied by plant roots, they are the pipelines channelling minerals extracted from the soil parent material as well as nutrients freed up via the digestion, excretion and decomposition of all parts of the microscopic food chain, from bacteria all the way up to earthworms.
“Microbiology feeds the plants, and the plants feed the microbiology.”
The soil critters may be small, with anywhere from 300 million to one billion in half a teaspoon of soil, but when they work together under the right conditions they have enormous power for decomposing organic matter and cycling and distributing nutrients in the root zone, he said.
Protozoa, which as single-celled organisms occupy the middle range of the food chain, are responsible for 40 per cent of the net mineralization of nitrogen.
That happens when a protozoan with a carbon-to-nitrogen ratio of 30:1 in its physical makeup eats bacteria with a C:N ratio of 5:1. When it excretes or dies, it releases the surplus nitrogen molecules in a plant-available form into the soil. Multiply that by the untold billions of the bugs in healthy soil, and a “tremendous” amount of nutrients becomes available to feed a crop, he said.
Nematodes, a type of microscopic worm, have a C:N ratio of 100:1. They feed on bacteria, fungi, protozoa, and roots. Larger than other soil bugs, they make tunnels, creating aerobic conditions in the soil. Some types are “cannibals,” and eat other nematodes.
“One type we like to call a ‘switcher.’ He feeds on fungi, but if there’s no fungi in the system, he turns around and starts eating roots. You can see why this would be bad, because he comes up to the roots and sucks nutrients right out of the root,” said George.
“When he’s done, he leaves a nice little hole for plant pathogens to get in.” [email protected]