Hedgerow species and environmental conditions effects on soil total C and N and C and N mineralization patterns of soils amended with their prunings

An important criterium in selecting species for alley cropping is the mineralization pattern of their prunings. This study determined effects of 5 years of hedgerow pruning applications on soil organic C and total N at three locations in Haiti and mineralization patterns from soil amended with the prunings during an incubation using micro-lysimeters. Soils (0-5 cm) under 5 hedgerows were collected at each site and analyzed for organic C and total N. In the laboratory, ground leaves and stems (<1 cm diameter) of the hedgerow species were mixed with soil at rates of 3 and 1.5 Mg ha(-1), respectively, and aerobically incubated in the dark at 25 T. A non-amended soil was used as control. Soils were leached to determine mineral N at 1, 3, 7, 14, 28, 42, 84 and 120 days of incubation. Evolved CO2 was measured following each leaching procedure. At the calcareous site, application of prunings from Leucaena leucocephala (Lam.) De Wit and Delonix regia (Boj. ex Hook. Raf.) resulted in 23 and 13% higher soil N than the control, respectively, after 5 years. There were no differences in total N at the other sites but soil N was highest under Leucaena hybrid and Acacia angustissima (Mill.) Kuntze, respectively at the basaltic and high elevation sites. Soils under D. regia (calcareous) and A. angustissima and Leucaena hybrid (high elevation) had higher organic C than the respective controls. Carbon and N mineralization and C turnover were highest when soils were amended with leaves of Leucaena diversifolia (Schlecht.) Benth (calcareous and basaltic soils) and A. angustissima (high elevation) and lowest in non-amended control soils. Stem-amended soils showed differences in C mineralization for calcareous and high elevation soils whereas N mineralization was similar among treatments within sites. Carbon and N mineralization (high elevation soil) correlated positively with N concentrations of leaf prunings. Amendments with leaf prunings increased soil C and N mineralization and turnover rates, suggesting greater nutrient availability for the crop during a short period than in non-amended control soils.