Carbon and nitrogen cycling in alley cropping systems in Haiti

Alley cropping, the growing of crops between rows of leguminous trees or shrubs, has been used to sustain crop yields in the tropics. The objectives of this study were (i) to assess suitability of tree species as hedgerows for alley cropping in terms of amounts and rates of N release in three environments, (ii) to assess effects of hedgerow management on soil C and N dynamics and (iii) to determine optimum hedgerow management that improves maize (Zea mays) yield and N-recovery.; Five hedgerow species were selected on the basis of biomass yields for C loss and N release studies at each site. Species differed in C loss and N release patterns within sites. Initial leaf N concentrations correlated with C loss (phase I) whereas (lignin + polyphenol):N correlated negatively with N release rates (phase II).; Application of prunings of Leucaena leucocephala and Delonix regia (calcareous site) Leucaena hybrid (basaltic site) and Acacia angustissima (high elevation) led to greater soil organic N than in control plots after 5 years. Stem-amended soils showed similar N mineralization among treatments within sites.; Cumulative effects of Leucaena hedgerow management (pruning utilization by pruning regimes) on soil organic C and N dynamics were determined. Pruning application had greater organic C and N and potential mineralization than the control in the 0–5 cm soil layer. Addition of fertilizer did not increase soil organic C and N but, enhanced soil N mineralization.; Application of Leucaena prunings increased maize yield and grain N uptake. Yield declined over seasons in the control and where prunings were removed. Addition of inorganic fertilizer increased further yields and N-recovery by maize. Over seasons, three-cut regime had higher maize yields and better % N-recovery than the two-cut regimes. Low N-recovery under the two cuts made at planting and 40 DAP indicated tendency for N immobilization under this pruning regime. (Abstract shortened by UMI.)...