Decomposition and nitrogen release of prunings from hedgerow species assessed for alley cropping in Haiti

Decomposition and N release patterns from prunings of eight tree species we re studied under field conditions. Leaves and stems (<1 cm diam) from 4-yr- old hedgerows were sealed in separate litter bags and placed on soil surfac e at Low and high elevation (1150 m) sites in Haiti. Leaves decomposed fast er than stems and leaf decomposition was described by a two-pool exponentia l model. At the low elevation, leaf C loss was highest (82%) in gliricidia [Gliricidia sepium (Jacq.) Kunth ex Walp.] and lowest (42%) in flamboyant [ Delonix regia (Bojer ex Hook) Raf.] after 48 wk. At the high elevation, lea f C loss after 48 wk was 48% in leucaena [Leucaena leucocephala (Lam.) De W it] and 29% in Acacia angustissima (Mill.) Kuntze. Initial N concentrations correlated with leaf C loss (Phase I) at low elevation while C:N and ligni n:N correlated with leaf C loss (Phase II) at low and high elevations, resp ectively. Nitrogen release resembled carbon loss. At the low elevation, gli ricidia, Leucaena shannonii Donn. Sm., and leucaena released >50 kg N ha(-1 ) during the first 4 to 6 wk, whereas at high elevation A. angustissima con tributed <40 kg N ha(-1) during the period. Leaf N release correlated negat ively with (lignin + polyphenol):N at low elevation. At the low elevation, gliricidia, L. shannonii, and leucaena provided adequate N for maize produc tion in alley cropping. At the high elevation, A. angustissima contained ad equate N, but N release rate may not meet peak N demands of an associated c rop.