Interaction of earthworms and enchytraeids in organically amended soil

A laboratory study was conducted with soil microcosms to deepen our understanding on earthworm and enchytraeid decomposition activity regarding soil fertility improvement in sustainable agricultural management systems. We investigated the effects of different earthworm and enchytraeid species and their interaction on the consumption and decomposition of barley straw and cattle manure, commonly used as organic amendments in agriculture. In total, 55 microcosms were set up covering the following treatments: straw of three length classes (2.5 cm, 5 cm, 10 cm), two length classes (2.5 cm, 10 cm) and cattle manure which were offered to earthworms (Lumbricus terrestris, Aporrectodea caliginosa); enchytraeids (Enchytraeus crypticus, Enchytraeus christenseni); mixed earthworms and enchytraeids (L. terrestris, A. caliginosa, E. crypticus, E. christenseni); no animals (control). After 45 days of dark incubation at 15oC the consumption rate, soil microbial biomass, pH, nitrogen (N-NH4+, N-NO3-, Nt), and organic carbon were measured. The results indicated that mixed faunal treatments revealed the highest consumption rate. Short straw was consumed preferentially in all treatments. Earthworms increased microbial biomass and contents of N-NO3- and N-NH4+. In the enchytraeid treatments soil microbial biomass and organic carbon were lower compared with control, while soil nitrate was lowest when straw was used as organic source. Soil fauna in the mixed treatment reduced soil microbial biomass, N-NO3- and soil organic carbon content. It is concluded that earthworm-enchytraeid-interactions might have important impacts on soil fertility.