In plots that had been no-tilled since 1983, she found an average 170 earthworms per square metre. In plots that had been no-tilled until 1996 and then were fall plowed and spring disked, there were only 22 earthworms per square metre. Almost 90 per cent of the earthworm population vanished because of the single year's plowing after 13 years of no-till. Indeed, the earthworm population dropped nearly as low as in plots that had been plowed every year since 1983. Fox believes that with more years in no-till, earthworm numbers would keep climbing.
Dew worms can tunnel as deep as five feet.
In other words, they mix the upper soil layers, much like a mouldboard plow. As well, earthworms drag crop residues and plant debris from the soil surface down into the burrows. On soils with good earthworm numbers, it's a key reason why soybean leaves disappear so quickly after leaf drop, Fox explains. Fortunately, no-till is inherently kind to earthworms. Crop residues provide food and keep the soil surface cool and moist.