Millipedes and earthworms increase the decomposition rate of 15N-labelled winter rape litter in an arable field

Effects of millipedes and earthworms on the decomposition of N-15-labelled litter of winter oilseed rape were investigated in a microcosm field experiment over a period of 264 days on an oat field near Gottingen managed by integrated farming. A total of 32 microcosms were filled with defaunated soil. N-15-labelled rape litter was placed either on top of the soil or buried into the soil simulating mulching and ploughing, respectively. To the microcosms nine adult individuals of Blaniulus guttulatus (Diplopoda) and two of Aporrectodea caliginosa (Lumbricidae) were added separately or in combination. In general, the presence of the animals accelerated the decomposition rate of the litter material. The effects were most pronounced in the presence of Aporrectodea caliginosa. The total amount of nitrate, ammonium and the amount of N-15 leached from the microcosms was increased in the presence of earthworms or of both earthworms and millipedes, Both species proved to be important members of the detritus food web of the agricultural system studied.