RESPONSES OF EARTHWORM ABUNDANCE AND PRODUCTION OF SURFACE CASTS AND THEIR PHYSICOCHEMICAL PROPERTIES TO SOIL-MANAGEMENT IN RELATION TO THOSE OF AN UNDISTURBED AREA ON A SEMIARID TROPICAL ALFISOL

Population densities of earthworms and their surface cast production w ere sampled across 15 soil management treatments such as annual tillag es with organic amendments and perennial ley treatments during 1989-93 in a semi-acid tropical Alfisol. They showed significant reduction in their densities in annual treatments due to carbofuran and herbicide application during July 1989. In 1992, densities recovered from insect icide stress after 3 years, and showed significant temporal and spatia l variation across the treatments, being higher during the post-rainy season. Soil management practices significantly affected the densities which were higher in zero-tillage farmyard manure treatment and in ze ro-tillage Stylosanthes and pigeonpea and Stylosanthes treatments amon g the annual and perennial treatments, respectively. Surface cast prod uction of earthworms was higher in 1992 than in 1993, and was signific antly affected by the annual treatments (P < 0.05). However, the physi co-chemical properties such as pH, electrical conductivity (EC), organ ic C, total N, available P, available K, Na, Ca and Mg of casts were n ot affected by the annual and perennial treatments. The densities of e arthworms, and their surface cast production were significantly greate r in a natural revegetation area than those in the arable area under s oil management, while most of the physico-chemical characteristics of casts were higher than those of the underlying soil in both arable and natural revegetation areas. (C) 1997 Elsevier Science Ltd.