Effects of tillage and straw treatments on earthworm abundance : study in two Swedish long-term field trials

Earthworms have several functions in the soil, for instance redistribution of organic matter and enhancing plant available nutrients. Earthworms are divided into three ecological groups, with different functions in the soil. The groups are: anecic, endogeic and epigeic. Studies has shown that tillage practices effect the earthworms, where often reduced tillage increase earthworm abundance in comparison to inversion tillage. However, the ecological groups of earthworms respond different to tillage method, where endogeic earthworms are less effected, in comparison to the anecic earthworms, which are more sensitive to an intensive tillage. The aim of this study was to compare tillage treatments (conventional tillage, reduced tillage, and no-tillage) and straw treatments (incorporated straw or removed straw) regarding the earthworm abundance, and their relationship to soil properties. Five treatments were included in this study; conventional tillage with straw removed or incorporated, reduced tillage with straw removed or incorporated and no-tillage. Earthworms and soil properties (aggregate stability, basal respiration, penetration resistance and carbon, nitrogen, and phosphorus content) were measured in two long-term field trials near Lanna experimental station, in Lidköping, Sweden. The results showed that the abundance of earthworms in total and juveniles where highest in the no-tillage treatments, and conventional tillage showed the lowest abundance for earthworms in total and juveniles. Also, earthworm biomass where highest in the no-tillage treatments. The abundance of adult and endogeic earthworms was highest in reduced tillage with straw incorporated, between the four other treatments there was no difference for the abundance. We did not see any effect of straw treatment in conventional tillage and no-tillage, however, in reduced tillage the straw treatments influence the abundance of adult and endogeic earthworms. Our study indicates that there is no difference between no-tillage and conventional tillage regarding the endogeic and adult abundance, but regarding the total abundance no-tillage is more favourable. Among the soil properties, turbidity/aggregate stability and total soil carbon was for instance correlated with earthworm biomass, and abundance of total earthworms and juveniles. Keywords: anecic, conventional tillage, endogeic, no-tillage, reduced tillag