Contribution of earthworm activity to the infiltration of nitrogen in a wheat agroecosystem

The effect of earthworms on leachate volume and leachate N losses was investigated in a rice - wheat rotation agroecosystem over the wheat growing season. Corn residues (< 2 cm) were added to field microcosms as either mulch or incorporated into the soil. Earthworms were added to half of the microcosms at a population density and age structure simulating a natural earthworm population. With earthworms present, leachate volume was > 30% higher, but this result was not statistically significant ( P> 0.05). Earthworms significantly increased mineral N losses in the mulching treatment ( P< 0.05). There was a reduced fertilizer N ( urea-N-15) loss when earthworms were present, but the reduction was not significant ( P> 0.05). Our results indicate that earthworm activity can accelerate leachate production and N loss to a certain extent under wheat, and that native soil N ( including mineral N and organic N) and/or organic matter N ( corn residue N) are more likely sources for N leaching than urea-N.