INFLUENCE OF THE ENCHYTRAEID WORM BUCHHOLZIA-APPENDICULATA ON AGGREGATE FORMATION AND ORGANIC-MATTER DECOMPOSITION

Enchytraeid worms were kept in <0.3 mm sieved sandy loam subsoil mixed with ground wheat, for 6 weeks at 16 degrees C. Sieved soil with orga nic matter but without worms was also incubated. The soil was then all owed to air-dry slowly during 6 weeks. Enchytraeid casts were collecte d from the surface of the soil with wens, and the remaining soil was s eparated into three size fractions by dry sieving. All size fractions were analysed for stability and %C, and mineralisation potential. The amount of soil in the fraction >0.3 mm (including the casts) was large r in the presence of enchytraeid worms, at the cost of soil from the f raction 0.3-0.03 mm. The %C in both soils was highest in the fraction <0.03 mm. Activity of enchytraeids significantly decreased the %C in t he fraction >0.3 mm. Fresh excrements, representing 0.5% of the soil, were very high in organic matter content. Mineralisation (expressed as percentage of C that was mineralised) was highest in the Fraction <0. 03 and lowest in the 0.3-0.03 fraction. Excrements showed very high mi neralisation rates. Enchytraeid activity enhanced mineralisation in th e fraction >0.3 mm. Aggregates >0.3 mm from the treatment with worms d ispersed less clay after shaking with water than those from the treatm ent without worms. Although the influence of enchytraeid worms on tota l C-content and mineralisation was small, the changes in C of the diff erent size fractions showed that enchytraeids influenced the active fr action of the C in the soil considerably by consuming litter, thereby locating it inside soil aggregates and linking the organic matter to c lay par tides. (C) 1997 Elsevier Science Ltd.