Depth of planting also has a profound effect on seed warmth. Early in the season, soil temperature drops quickly with increasing depth. Keeping the seed relatively shallow can speed germination significantly. Many no-tillers like to plow their fields every four to six years to help spread organic matter and fertilizer through the soil profile. This is the time of year, however, when growers can start seeing the price they pay for not leaving the plow in the barn.
Evidence shows that plowing no-till soils is deadly for earthworms.
That's a loss, says Cathy Fox, soil fauna scientist for the federal agriculture department at London, because in no-till fields, earthworms are crucial for the vertical movement of air, water, nutrients and organic matter. Earthworms also play a major role in improving the stability of soil aggregates in no-till soils, making them more resistant to erosion and crusting. Fox counted earthworms last year in long-term tillage plots on Brookston clay loam at Woodslee. 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.