Decomposition and nutrient release from intra-specific mixtures of legume plant materials

Because farmers use mixtures of leaves and stems as a soil amendment, data of leaves, stems, and a leaf/stem mixture of Indigofera constricta and Mucuna pruriens from a 20-week litterbag study were analyzed to assess their decomposition, nutrient release, and possible interactions within mixtures. Decomposition and nitrogen (N)-release patterns were leaves >= mixtures >= stems, whereas phosphorus (P)-release patterns were the opposite (P < 0.05). Leaves released 110-130 Kg N ha(-1), and mixtures released 30% less. A similar ratio was obtained for P release. This suggests that nutrient release from leaf/stem mixtures is overestimated when only leaves are considered. Decomposition and nutrient-release patterns of mixtures occasionally differed from estimated patterns by 2-5% (P < 0.05), indicating that minor interactions took place. However, estimations based on the amount of released nutrients generally showed non significant interactions. This suggests that the impact of low-magnitude interactions within mixtures during its decomposition on soil fertility are negligible when considering total nutrient release.