Evaluation of Inga spp. for dinitrogen fixation and nitrogen release in humid -tropical alley cropping

Inga spp are tropical legume trees traditionally used for shade in coffee and cacao plantations and have potential for hedgerows in alley-cropping practices. Little information can be found concerning the N2-fixation of these species. The rhizobia that nodulate Inga edulis Mart was characterized using standard laboratory procedures and DNA analysis. Dinitrogen fixation of I. edulis was determined by the 15N isotope dilution technique. Mathematical models were used to evaluate the rate of decomposition and N release of I. edulis and I. samanensis Uribe leaves. The production of green mulch and firewood of I. edulis and I. samanensis were evaluated in an organic-corn alley-cropping practice in the humid tropics. Inga edulis is nodulated by a fast growing Bradyrhizobium sp. and is a N2-fixing tree. Inga edulis and I. samanensis produced similar amounts of mulch, N content in the mulch, and firewood. Inga samanensis leaves decomposed faster and released more N than I. edulis leaves, but this difference in N release did not affect the corn yield. In 2001, corn yield in the monocrop was higher than in the alley cropping, but was equal in 2002. Inga edulis and I. samanensis had similar characteristics and showed to be well situated for organic-corn alley cropping in the humid tropics.