LEAF LITTER DECOMPOSITION DYNAMICS OF THREE SELECTED TREE SPECIES IN HOMEGARDEN AGROFORESTRY OF WONAGO DISTRICT, SOUTHERN ETHIOPIA

<strong>ABSTRACT</strong>: In traditional agroforestry system of Gedeo zone, farmers believe that Croton macrostachyus, Erythrina brucei and Millettia ferruginea are more significant than other tree species to maintain soil fertility as well as crop yield improvement. However, leaf litter decomposition dynamics of these tree species have not been given research attention. Therefore, the major objective of this study was to determine leaf litter decomposition dynamics of C. macrostachyus, E. brucei and M. ferruginea in homegarden agroforestry of Wonago district. Three Kebeles namely Haseharo, Tokocha and Wonago Town were selected purposively using field observations. Litterbag experiment was employed to study the leaf litter decomposition dynamics. A total of 108 litter bags were used for the litterbag experiment at the three study sites. Two litter bags from each tree species were randomly retrieved 6 times at two month intervals in a year from March 2018 to March 2019. In situ decomposition revealed that the %mass loss of leaf litter after one year decomposition period varied between 13.5 and 99.5%, 11.5 and 82.1%, and 8.0 and 73.3% in the case of C. macrostachyus, E. brucei and M. ferruginea respectively. The species (P &lt; 0.001) have shown significantly related with %mass loss, but the site was not shown (P = 0.263). The values of decay constant (k) were varied from 0.15-5.29, 0.12-1.72 and 0.08-1.32 for C. macrostachyus, E. brucei and M. ferruginea respectively, and have shown significant relation with %mass loss (P &lt; 0.001). Half-life period (𝑡0.5) of the three tree species, varied from 0.131-3.938 for C. macrostachyus, 0.942-5.133 for E. brucei and 1.335-10.50 for M. ferruginea, in the three study sites was different. Soil moisture (P &lt; 0.001), soil temperature (P = 0.007) and soil pH (P = 0.014) revealed statistically significant effect on the leaf litter decomposition dynamics. The highest amount of SOC 7.10%, 4.96% and 3.55% at initial retrieval period and the lowest values of SOC 6.87%, 4.44% and 2.48% were recorded for HH, TO and WOT respectively at final retrieval period. Dry and rainy seasons were a more powerful determinant in leaf litter decomposition dynamics. Soil pH and soil temperature have been effect on the leaf litter decomposition. And, SOC shown an increasing with increasing of altitude. Generally, further study could be needed on nutrient releasing and microbial effects on leaf litter decomposition.