Abstract

Multiple forms of biomass, including litter, herbaceous, and woody biomass emanating from agroforestry systems, have numerous environmental and socioeconomic benefits, including improved soil health, biodiversity, carbon sequestration, and diversified income. These benefits are crucial to sustainable production. Despite agroforestry's significant contribution to sustainable food production, less attention is given to litter mass decomposition and its mechanisms of nutrient release and cycling. A study to assess the influence of agroforestry litter quality on decomposition and nutrient release in acidic soils of Uasin Gishu County, Kenya, was conducted at the University of Eldoret. The hypothesis was that the litter type of three agroforestry species - Gliricidia, Leucaena, and Sesbania - affects the rate of decomposition, nutrient release pattern, and the chemical characteristics of acidic soils. Results from the study revealed a significant (P≤0.05) influence of agroforestry litter type and initial litter quality on the rate of decomposition and nutrient dynamics in the order of Sesbania > Gliricidia > Leucaena. Sesbania showed superior litter quality, recording the highest OC (48.1%), N (25.9 g kg-1), and Cu (0.35 ppm), and the lowest concentration of lignin (18.0%), cellulose (24.0%), and the lowest C:N, L:N, L:PP, L:P:N, and L:N:P ratios, hence the highest rate of decomposition (k=0.04). Nutrient release was in the order of Fe=Cu>K>Ca>Mg=Mn>N=Zn>P for Gliricidia, Ca>Cu>K=Mn>P>Zn>N for Leucaena, and Ca>Cu>Mn=Mg>P=K>N>Zn for Sesbania. Although there were no significant differences in nutrients released from the three litter types, Sesbania recorded the fastest release of N, P, Cu, and Mn, contributing about 3.2% SOC, 25.5 kg P ha-1, and 11.4 kg K ha-1 to the soil. Mean soil enrichment (ER=1.1, 1.5, and 2.5) for SOC, P, and K, respectively, indicates the potential of agroforestry litter mass of Sesbania sesban in nutrient cycling. These findings provide insights into the crucial role of agroforestry litter in the cycling of macro and micronutrients, hence enhancing soil ecosystems and sustainable production. However, further studies involving different litter types in multiple agroecological zones are needed to assess the impacts of other environmental factors on nutrient release mechanisms in acid soils.

Key words: Climate change mitigation, enrichment ratios, litter chemistry, nutrient cycling, soil ecology.