Litter Deposition and Decomposition in a Tropical Grass-Legume Silvopastoral System

This study hypothesized that the deposition and decomposition of the litter from the legume tree Mimosa caesalpiniifolia Benth. could improve and accelerate nutrient cycling in a tropical pasture (Urochloa decumbens Stapf.) under a silvopastoral system. The objective of this study was to evaluate litter deposition, chemical composition, and decomposition of the legume tree M. caesalpiniifolia. Treatments included a silvopastoral system with signalgrass (U. decumbens) combined with the legume tree M. caesalpiniifolia, and monocropping systems of both species, in a randomized complete block design with three replications. It was evaluated litter deposition from legume trees over two years. A decomposition assay evaluated leaf decay of the legume and grass (0 to 512 days), incubated under different cropping systems (silvopastoral and monoculture), and at different distances away from the legume trees (0 and 2 m). Greater litterfall was recorded in the legume tree monoculture system (534 kg ha^− 1) and during the dry season (541 kg ha^− 1) (p < 0.05). The silvopasture system induced N release from the grass litter under decay. After 512 days, incubated grass leaves still had 30% of decaying material, while the legume had about 39%. The remaining N in the litter increased, and the C and C/N ratio decreased over the incubation period. Legume trees have the potential to diversify nutrient cycling in tropical pastures, due to high N and lignin content, and low C/N ratio compared to grass. The presence of legume trees can create zones with different nutrient return rates along the pasture.