Nutrient content of earthworm casts influenced by different mulch types

The aim of this study was to investigate the effects of different mulch types on the quality and quantity of casts of different lumbricid earthworm species. Nutrient contents (organic carbon C-org, total nitrogen N-t and inorganic phosphate Pi), and acid phosphatase activity (SPA) of earthworm casts and soil aggregates were measured and then compared. This short time experiment was conducted in the laboratory, simulating field conditions of mulch management in temperate agroecosystems. In microcosms, the two common field species Lumbricus terrestris and Octolasion cyanuem were inoculated. Barley, lupin, maize, or sugar beet were used as mulch according to amounts usually applied in the field. Nutrient contents and phosphatase: activity in worm casts were generally enhanced compared to the soil. Nutrient values were higher in the casts of the detritivorous L. terrestris than those of the geophageous O. cyaneum. Conversely, the phosphatase activity was increased in the casts of O. cyaneum compared to L. terrestris is in case of the barley and sugar-beet treatments. Cast production was related to the earthworms' change of biomass (Delta B) as well as, in the case of L. terrestris, to nitrogen content of the mulch. Due to their chemical compounds, the mulch types influence both the food selection of the worms and the acceptance by microorganisms. (C) 1999 Editions scientifiques et medicales Elsevier SAS.