Effect of different plant litters and low-dose gamma irradiation on the biological activity and vermicomposting potential of two aboriginal earthworm species of Azerbaijan

Abstract

Earthworms are among the most important pedobionts of soils and play a crucial role in the conversion of organic matter and in humus formation. This study evaluated the effect of different plant substrates and of low-dose gamma irradiation on the feeding activity, coprolite production and compost-forming potential of two aboriginal earthworm species of Azerbaijan, Eisenia foetida and Nicodrilus caliginosus trapezoides (Sav.). Worms were cultured for 48 days in aerated plastic containers at 60–70% moisture. Four substrates were tested: alfalfa residues, grape leaf litter, natural grass litter and sagebrush ( Artemisia ) residues. In addition, N. caliginosus trapezoides individuals were exposed to acute gamma doses of 3, 5, 15 and 20 Gy and were monitored for behavioural response, survival, biomass change and qualitative changes in the coprogenous structure of the soil. Substrate type strongly affected feeding and excretion. E. foetida showed higher overall consumption (3.1–7.6 g), with the greatest processing on natural grass litter (7.6 g). N. caliginosus trapezoides consumed less substrate (1.66–2.35 g) but produced markedly more coprolites (44 g at day 28 and 132 g at day 48). Doses of 3–20 Gy did not reduce survival; the low doses stimulated feeding, the high doses induced a protective secretion response.