Earthworm populations and growth rates related to long-term crop residue and tillage management

This study evaluates the effects on earthworm populations of three tillage systems (moldboard plow/disk harrow (CT), chisel plow or disk harrow (RT) and no tillage (NT)) with high or low crop residue input levels. In the soil cores sampled from the field trials, NT plots had greater earthworm populations and biomass, but crop residue level showed no effect. However, laboratory trials with intact soil cores showed that both decreased tillage disturbance and increased residue input positively impacted earthworm growth. The positive correlation between earthworm growth rates and available soil organic C pool suggest that the availability of organic substrates for earthworm food is a significant factor controlling earthworm populations. The authors conclude that in cool, humid agroecosystems soil disturbance from tillage appears to have more influence on earthworm populations than food availability.