Nitrogen transformations associated with earthworm casts

• Published in: Soil biology & biochemistry 1994, Vol.26 (9), p.1233-1238
• Main Authors: Parkin, Timothy B., Berry, Edwin C.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Aporrectodea tuberculata; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(94)90148-1

Earthworms are intimately involved in the cycling of C and N in soil. Earthworm casts are enriched in mineral N; however, there have been few studies of the dynamics of microbial N transformations associated with earthworm casts. We evaluated the N-transformations in earthworm casts as affected by organic residues used as a food source by earthworms. Denitrification rate, nitrification potential and mineral N content of the casts of two earthworm species ( Octolasian tyrtaeum Savigny and Aporrectodea tuberculata Eisen) were assessed in laboratory trials. Trials were made in plastic chambers (600 g soil) with three organic-C treatments: 20 g fresh hairy vetch ( Vicia villosa Roth), 5.5 g air-dried hairy vetch or 5.5 g air-dried horse ( Equus caballus) manure. Earthworm casts were enriched in mineral N, relative to surrounding soil, and that the amount of N accumulated in earthworm casts was a reflection of the N content of the organic matter used as a food source by the earthworms. Casts had elevated denitrification rates, compared to soil, however, rates were low relative to the elevated NO 3 − concentrations in the casts (80–100 μg NO 3 −-Ng −1 dry wt). Observed denitrification rates appeared to be related to the quality of organic matter available to the earthworms, but were not significantly affected by species of worm.