Feed The Soil So It Can Feed The Crop

Crop yields in a slump? Disease and insect probalems rife? Input costs chewing up profit margins every year?

Before you cur se the weather, bugs, or chemical companies, you might want to consider another cause: Declining soil quality.

Modern farming has developed a host of quick-fix solutions but the beneficial effects are temporary if you ignore soil health, according to Jill Clapperton, a rhizosphere ecologist who worked for 16 years as a research scientist at AAFC, and now runs Earthspirit Consulting in Montana.

Soil isn’t just a layer of ground-up rocks and water, but a living system created over the eons by unfathomably complex interactions of plants; countless trillions of bacteria, fungi, and single-celled creatures; and earthworms and all sorts of bugs.

“When you stand on the ground, you really are standing on the rooftop of a whole other world,” Clapperton told farmers attending the Manitoba-North Dakota Zero Tillage Farmers Association annual workshop.

When disturbed by excessive tillage, fallow, overuse of chemicals, overgrazing, or overly tight monoculture rotations, the system becomes unbalanced. The result is pest infestations, poor nutrient cycling due to low organic matter levels, and weakened “tilth” or soil structure.

The good news is that with time and good stewardship, damaged soil can be rebuilt, she said.

Jethro Tull, a 17th-century founder of modern agriculture, figured plowing virgin sod made for good crops. It did, because the plow tore open the soil food web like a “tsunami” through a seaside town, leaving the shattered remains to rot and feed the crop.

“The only problem that he hadn’t figured out was that if we kept doing that, we would just keep depleting and depleting until the soil went from nine per cent organic matter to half a per cent,” said Clapperton.

“Now what do we do? We go to no till.”

No tillers have a head start once they stop disrupting the natural system and start feeding the soil with the goal of increasing their carbon-nitrogen ratio to the optimal 20:1 to 30:1 required for nutrient mineralization. You must also keep something green on the field at all times – using cover crops to fill in gaps where possible – because “fallow is death,” she said.

Making cover crops pay might require the introduction of above-ground livestock to complement their much smaller underground counterparts.

The first five years of no till aren’t for the faint of heart, because initial gains are hard to see as “bio-remediation” gradually resuscitates life in the soil, she said. One of the first problems farmers face is compaction. Forget deep rippers.

Instead, Clapperton advises planting deep-rooted crops such as daikon radishes to break up the hardpan. Big roots are also one of the best ways to boost organic matter levels.

“Biologically priming” the soil starts with the smallest critters, the bacteria and fungi. Once the prey are available, the predators such as beneficial nematodes, mites and protozoa follow. They poop out what they can’t use as tiny pellets, which build soil structure.

“You are managing a living, dynamic system. Feed it a balanced diet,” she said. “With better structure, we’ve got better habitat for the bacteria and the protozoa. We’re starting to get the soil really functioning, and that’s what we’re looking for.”

The first three to five years are for “fattening up” the soil life. Earthworms – a “great indicator of soil biology” – may appear at this point. They aerate the soil, mixing it up, and leaving tunnels filled with sugary slime that plant roots adore.

At six to 10 years, crop residues may begin disappearing too fast. That means more carbon needs to be added by planting more cereal crops.

Insecticides sometimes make economic sense, but she urges farmers to remember that they are the “worst thing” for the soil, and fungicides kill not only fungi, but also earthworms. But at this point, beneficial insect

populations may reduce the need for sprays.

At 11 to 20 years of good no-till practices, the farmer starts to see that he doesn’t need to use as much fertilizer and other inputs, and now turns towards “consolidating the habitat.”

“This is where it gets really fun,” said Clapperton. “We’re knocking back on the amount of fertilizer we use, our soil is working, we’ve got an increased cation exchange capacity, and we’re starting to see the changes.” daniel. [email protected]




About the author



Stories from our other publications