Promising tree species as hedgerows for alley cropping in different environments in Haiti
Alley cropping is a system whereby annual crops are planted between rows of trees, which are pruned during the cropping season and the prunings applied as mulch or green manure. During periods where no crop is grown, the trees are allowed to grow freely. A total of 37 hedgerow species were tested in Haiti for biomass production under annual rainfall regimes ranging from 700 mm to more than 2,600 mm and from near sea level to 1,200-m elevation. At all low-elevation sites, regardless of rainfall amount or soil type, Leucaena leucocephala and related species were the most productive in terms of total and leaf biomass. L. leucocephala and Gliricidia sepium were the best sources of N. At both high-elevation sites, Acacia angustissima was by far the most productive species in terms of biomass production, and also the N supplied through decomposition. Calliandra calthyrsus appears to have potential at high-elevation humid sites but was not productive at the high-elevation site with moderate rainfall. Where grazing of hedgerows by ruminants is a major problem, Delonix regia was shown to have potential for low-elevation sites. However, because it does not fix N, another source of N should be supplied. Major differences were not observed in the effect of different hedgerow species on crop yields. Also, vigorously growing, competitive species may require more aggressive management in order to minimize competition to the crop.