Organic inputs from agroforestry trees on farms for improving soil quality and crop productivity in Ethiopia

摘要: Indigenous agroforestry trees and shrubs on farmlands are an under-utilized resource that can be used as green manures (GM) to alleviate declining soil fertility productivity. The aims of studies described in this thesis were investigate: (1) the seasonal dynamics chemical contents foliage from selected tree species potentially available sources GM, (2) rates patterns mineralization nutrients during decomposition leaves, (3) nutrient limitations for microbial processes Mollic andosols farm forest land-uses using respiration kinetics, (4) utility kinetics characterizing quality plant materials, (5) effect combined GM fertilizer inputs crop yield properties. two leguminous (Albizia gummifera G.F. Gmel Milletia ferruginea (Hochst.) Baker) non-leguminous (Cordia africana Lam. Croton macrostachyus Del.) species. Foliar N, soluble polyphenols (PL) condensed tannin (CT) higher wet season while those K lignin dry season. Green leaves had N P senesced ones K, cellulose, PL CT. On average, 27% 48% was resorbed senescence. In a study Albizia Cordia, mass loss, loss release CT than Cordia. However, immobilized first four weeks both High seemed have facilitated despite high initial leaves. Nitrogen more limiting micro-biota suggesting presence adequate amounts endogenous P. Addition excess resulted pattern with peaks, different pools being over time. substrate-induced respiration, specific growth rate microbially farm; % total added C respired (49-69%) land-use indicating increased costs utilize strongly bound nutrients. Under laboratory field conditions, 11%-44% 10%-42% leaf mineralised within month, respectively, ranking as: Cordia < Croton. Supplemental little mineralization. manure caused increase maize by 10-84%, which apparently their Milletia. Measurable improvements pH organic due also observed at end short–term (2 y) trial.