By ANN HINCH
INDIANAPOLIS, Ind. — To call someone a “worm” is generally considered an insult, but Odette Menard doesn’t find the earthworm repellant – and she said neither should no-till farmers, for several reasons.
The agronomic engineer, who works for the Quebec Ministry of Agriculture, said about 20 years ago, the Canadian government set out to show farmers the economic advantages of soil conservation. Menard talked to a large crowd at the National No-Tillage Conference in Indianapolis earlier this month about something soil conservationists like her discovered when trying to institute no-till to save eroded land.
They came across a no-till farmer who they learned was applying less nitrogen but getting the same yields as area farmers who tilled. They found a number of middens on his land, which are the clumps of crop residue, leaves, straw and other organic waste one might find that look like tiny hills with part of the material even pulled down into the ground.
Middens are connected to tunnels earthworms “plow” underground – as homes, as highways, even as hideouts. Intrigued, Menard and her colleagues set up a camera at night and filmed the worms at work – from this followed the kind of study that eventually earned her a place in the 2005 Soil Conservation Council of Canada Hall of Fame.
Earthworms are efficient tillers; Charles Darwin notably recognized this almost two centuries ago, but worm appreciation stretches back much longer ago. There are a few thousand species worldwide, Menard said, and three categories. Epigeic worms are smaller than the ones we usually see aboveground. They work in the first few inches of soil near the surface.
Endogeic worms are larger and rarely come out of the soil. They work further down, to a depth of about 16 inches.
Anecic worms live even further down, never making it to the surface; their job is to build main vertical tunnels that can go down as far as 7-9 feet to the water table. Undisturbed by outside means, an anecic tunnel can exist for up to 30 years; these worms can live for 6-7 years.
In this way, it is possible to have up to 1.3 million worms living beneath a 10-foot-square area of ground, for example, containing just 12 middens, Menard said.
Just a ton of earthworms, she further explained, can produce 100 tons of castings (waste) and provide valuable drainage. They can provide a farmer with 4 pounds of nitrogen, 30 pounds of phosphorous, 72 pounds of potassium and 500 pounds of calcium.
In addition, every worm produces four times its weight in bacteria and fungi that can’t be seen but is nonetheless vital to “very high-quality organic matter.” From an efficient digestive grinding machine, the worm’s waste is fine and rich in nutrients.
“Once we get into no-till and leave residue on top of the soil,” Menard said, this decrease in soil disturbance fosters more productive earthworms. “As soon as I stop working the soil, I double the soil microbial biomass.”
She added after just a few years of no-till, worms can “turn around” a compacted 8-inch depth of soil by loosening it for growers.
Earthworms don’t just aerate dirt and improve its structure, she said. They aid its hydrology and help fight plant pests and diseases. Nor do they eat crop seed, she said, as one farmer who quizzed her was worrying could happen.
“The worst that’s going to happen is your root is going to shift,” Menard said, explaining worms actually munch on decomposing roots and open up pockets in soil around living roots to allow better circulation of nutrients and water for them.
Dead roots aren’t the only worm food. In her video referenced earlier, Menard captured images of worms crawling aboveground at night, seeking dead or dying organic matter to drag into middens for feeding – but they also pulled things such as dead crop leaves lying on the ground into their holes, which explains those sometimes-curious sights.
Another farmer had told her he was worried that left unchecked, earthworms could breed out of control. She said earthworm population is directly related to food supply, and as soon as worms reach their optimum number for the food available, population will hold around that level as long as food supply stays the same.
“We have the feeling ‘If I don’t plow it, nothing will do it,’” Menard said of many farmers. “We need to change that, and trust these little guys.”
On the other hand, while she prefers a no-till system, she doesn’t necessarily fault those who plow occasionally. “The problem is tilling year after year, after year,” she opined.