EARTHWORM BIOMASS RESPONSE TO SOIL-MANAGEMENT IN SEMIARID TROPICAL ALFISOL AGROECOSYSTEMS

Earthworms recorded during 1989-1993 across 15 soil management treatme nts, comprising three different tillage x three organic amendments (ba re, 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 r evegetation area three species were found, including the above two and Octonochaeta rosea (Stephenson). The earthworm biomass showed signifi cant temporal and spatial variations and was higher during the post mo nsoon period than in the early rainy season. No worm biomass was recor ded during the dry season. In the tillage and organic amendment treatm ents, the biomass was drastically reduced from September 1989 to Septe mber 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 a mendments. Thus the earthworm biomass varied significantly (P<0.01) ac ross the 15 treatments, indicating discernible effects of soil managem ent.