Evaluation of Leaf Litter Decomposition Dynamics and Nutrient Release in Tropical Agroforestry Systems in Enugu State

Leaf litter decomposition is a critical ecosystem process linking plant community composition to soil fertility in tropical agroforestry systems, and its evaluation in Enugu State, South East Nigeria, has important implications for sustainable land management. This study evaluated leaf litter decomposition rates, mass loss dynamics, and nitrogen, phosphorus, and carbon release patterns for leaf litter from five common agroforestry tree species: Leucaena leucocephala, Gmelina arborea, Gliricidia sepium, Terminalia ivorensis, and Tectona grandis, at three agroforestry farms in Enugu North, Igbo-Etiti, and Udi Local Government Areas. The litterbag method was employed, with mesh bags of 2mm mesh containing 10g of air-dried leaf litter incubated in each farm for 30, 60, 90, and 120 days. Mass loss percentage, carbon-to-nitrogen ratio, and nutrient release rates were calculated at each sampling interval. Results showed that Gliricidia sepium litter decomposed fastest (50% mass loss at 30 days), associated with its low carbon-to-nitrogen ratio of 14.2. Gmelina arborea decomposed most slowly (50% mass loss at 72 days). Nitrogen release preceded phosphorus release in all species. Cumulative nitrogen released from Gliricidia over 120 days was 89 mg/g initial litter, the highest among all species. Temperature and rainfall significantly moderated decomposition rates. The study concludes that Gliricidia sepium is the optimal agroforestry tree for accelerating nutrient release and soil fertility improvement in Enugu State agroforestry systems, and recommends its strategic planting in low-fertility plots.

Keywords: leaf litter decomposition, nutrient release, agroforestry, Enugu State, Gliricidia sepium