Biol Fertil Soils (1994) 17:45-50 9 Springer-Verlag 1994 M. Vikram Reddy 9 V. Ravinder Reddy 9 D. E Yule A.L. Cogle 9 P.J. George Decomposition of straw in relation to tillage, moisture, and arthropod abundance in a semi-arid tropical Alfisol Received: 2 November 1992 Abstract The decomposition of rice straw was studied in relation to straw moisture and the abundance of soil ar- thropods, such as Acarina, Collembola, and miscella- neous groups dominated by termites [Odontotermes obesus (Rambur) and Microtermes obesi Holmgren], across tillage treatments (no tillage, shallow tillage, and deep tillage) in Alfisols of the semi-arid tropics in India from August 1989 to July 1990. In the straw, across the treatments, Acarina were dominant (>70% of the total arthropods), and Collembola were a minor component. O. obesus and M. obesi foraged straw together under the cover of an earthern sheet. A larger number of arthro- pods was recorded during the rainy season, but they were either negligible or absent during the dry season. The abundance of arthropods and mass loss of straw was greater in coarse-mesh bags than in the fine-mesh bags. Their abundance was significantly affected by tillage treatments and season (P< 0.01). In the beginning, it was significantly greater in the no-tillage and shallow-tillage than in the deep-tillage treatment. The mass loss was 46% of the initial mass during the first 60 days, and more than 90~ after 330 days of decomposition. Tillage had a sig- nificant effect on mass loss, particularly after 330 days, and the no tillage treatment led to a greater mass loss. Multiple linear regression analysis revealed that the mois- ture content of the straw and the abundance of arthro- M.V. Reddy 1 (v:~) 9 V.R. Reddy Environmental Biology Laboratory, Department of Zoology, Kakatiya University, Warangal 506009, A.P., India M.V. Reddy 9 D. E Yule 9 A.L. Cogle 9 P.J. George International Crops Research Institute for the Semi-Arid Tropics, Patancheru 502324, A.P., India D. E Yule 9 A.L. Cogle Queensland Department of Primary Industries, Land Management Research Branch, RO. Box 6014, Rockhampton, Qld 4702, Australia 1 Visiting Scientist (under the Rockefeller Foundation Environ- mental Research Fellowship in International Agriculture) in Resource Management Program at ICRISAT, India pods had significantly affected the mass loss in both fine- and coarse-mesh bags across the tillage managements. Key words Rice straw 9 Decomposition 9 Soil arthro- pods 9 Moisture 9 Tillage 9 Alfisols 9 Semi-arid tropics Introduction Retention of crop residues on the soil surface is an impor- tant component of conservation-tillage and no-tillage sys- tems. This practice has been shown to reduce soil erosion and increase water infiltration in Alfisols in India (Yule et al. 1993). The mulches undergo decomposition wheth- er on or in the soil. This is an important functional pro- cess associated with the flow of energy and nutrient cy- cling in the agroecosystem. Decomposition is a complex process in which soil arthropods together with other soil animals and microorganisms make a major contribution. Evidence that soil arthropods are primary regulators of mass loss of litter and crop residues is based on the use of chemical agents that exclude or inhibit the activities of the soil animals in decaying materials (Santos and Whit- ford 1981; Seastedt and Crossley 1983). The exclusion of broad groups of organisms, also, has been achieved by physically covering the leaf material with a mesh (House et al. 1987; Reddy and Venkataiah 1989; Reddy and Toky 1990). The biomass of soil invertebrates is often small in agro-ecosystems compared to that of natural ecosystems and their functions are influenced by soil tillage and other management practices. It has been hypothesized that in- vertebrate activity and the interaction of invertebrates with microflora are increased by conservation tillage compared to conventionally tilled soils. Thus, House et al. (1984) and Stinner et al. (1988) proposed[ that with conservation tillage, surface-maintained crop residues can provide a continuous resource in space and time for many decomposer organisms. Recently, Friebe and Henke (1991) reported that a higher tillage intensity was associ-