LITTER DYNAMICS AND CUMULATIVE SOIL FERTILITY CHANGES IN SILVOPASTORAL SYSTEMS OF A HUMID TROPICAL REGION IN CENTRAL KERALA, INDIA

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Abstract
Litter dynamics and associated nutrient turnover were studied in 4–5 yr-old silvopastoral systems involving four fast growing multipurpose tree species (Leucaena leucocephala, Casuarina equisetifolia, Acacia auriculiformis and Ailanthus triphysa). Our objectives were to characterise the variations in amount and quality of litter, decay rates and release of nutrients through litter decomposition, and to evaluate the possible cumulative influence on soil physico-chemical properties. Annual addition of litter ranged from 1.92–6.25 Mg ha-1. Leucaena showed the highest NPK levels in leaf litter and Ailanthus the least. Results of a litter bag study revealed that residual litter mass declined either exponentially or linearly with time. Casuarina and Leucaena litter decomposed completely within 6-7 months. Regardless of species, K remaining in the decomposing litter mass showed an exponential decline over time while both N and P had brief accumulation phases during the course of decomposition. Five years of tree growth has apparently improved the soil organic C, N, P and K content.