Earthworm biomass response to soil management in semi-arid tropical alfisol agroecosystems

Earthworms recorded during 1989-1993 across 15 soil management treatments, comprising three different tillage x three organic amendments (bare, farmyard manure, and rice straw) and six perennial ley treatments, belonged to two endogeic species, Octochaetona phillotti (Michaelsen) and Lampito mauritii Kinberg, while in a nearby undisturbed natural revegetation area three species were found, including the above two and Octonochaeta rosea (Stephenson). The earthworm biomass showed significant temporal and spatial variations and was higher during the post monsoon period than in the early rainy season. No worm biomass was recorded during the dry season. In the tillage and organic amendment treatments, the biomass was drastically reduced from September 1989 to September 1991 after the application of carbofuran and some herbicides, and was significantly reduced during these two years compared to that of 1992. The maximum monthly earthworm biomass ranged between 2.5 and 17.9 g m(-2) across the treatments and increased several-fold in the nearby natural revegetation area (75.9 g m(-2)). It significantly increased in perennial ley treatments compared to annual treatments with organic amendments. Thus the earthworm biomass varied significantly (P less than 0.01) across the 15 treatments, indicating discernible effects of soil management eng