Role of the anecic earthworm Lumbricus terrestris L. in the distribution of plant residue nitrogen in a corn (Zea mays)-soil system

While the benefits of earthworms to crop production are widely acknowledged, the mechanisms involved are poorly understood. We examined the effects of an anecic earthworm (Lumbricus terrestris) on the distribution of plant residue N in a com (Zea mays)/soil system. Soil (mixed Ap and B horizons) mesocosms (10 cm diameter, 39 cm deep) were amended with N-15-labeled corn litter. inoculated with one earthworm per mesocosin (WORM) or none (CTRL), and pre-incubated for 1, 2 or 3 weeks. Earthworms and remaining plant residues were removed and sweet corn grown in the mesocosms in a greenhouse for 3 weeks. Litter, earthworms, shoots, roots and bulk and burrow soil were analyzed for total N and N-15. Plant and earthworm biomass were also determined. Earthworms had no significant effect on the N content of shoots, roots or bulk soil. Recovery of N-15 ranged from 92.6 to 101.9% in CTRL and 60.2 to 83.2% in the WORM treatment. The N-15 content of bulk soil in the WORM treatment was significantly higher than in CTRL and increased with pre-incubation time. Excess at.% N-15 of burrow soil was 10-100 times higher than in bulk soil. Incorporation of N-15 by shoots and roots was si nificantly higher in the WORM treatment and 9 increased significantly with pre-incubation time only in the WORM treatment. In WORM mesocosms pre-incubated for 3 weeks. the distribution of added N-15 was 9.8% in litter, 6.5% in plant, 31.5% in soil, 12.0% in earthworms and 39.8% presumably lost as gas: in CTRL mesocosms. the values were 75.7% in litter, 3.2% in plant, 13.7% in soil and 7.4% in presumed gas losses. The activities of L. terrestris altered the distribution of plant residue N significantly, increasing the transfer of N to plants and soil and enhancing losses of N in the gas phase as pre-incubation time increased. (c) 2005 Elsevier B.V. All rights reserved.