A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

The effect of lime and phosphorus on nodulation of the leguminous trees,Inga edulis and Gliricidia sepium in Amazonian agroecosystemsJessica Milgroom*, Erick Fernandes, Marco Rondon, Karen McCafferyCornell University*111 Donlon Hall, Cornell University, Ithaca NY 14853, jm120@cornell.eduThe Amazon rainforest is rapidly being converted to farmland and pasture. Many efforts are underway tounderstand the ecology of reforestation of deforested areas and the sustainable management of associatedagroecosystems. Nitrogen-fixing trees in small-scale agricultural systems play an important role inmaintaining and restoring soil fertility via minimizing soil erosion and nutrient leaching, and enhancingbiological N fixation. Trees in agricultural systems also provide fruits, fuelwood and fodder. This studyfocused on two N-fixing species, Inga edulis (native) and Gliricidia sepium (exotic) that are ubiquitous inforests as well as on farms. The low levels of available Ca and P in local soils can severely restrict rootgrowth, nodulation and N-fixation. I investigated the effect of fertilizer treatments: phosphorus, lime andphosphorus + lime on nodulation of I. edulis and G. sepium in a 2x2 randomized blocks field experiment54km north of Manaus, Brazil. In addition, two methods: soil auguring and trenches were compared forquantifying nodulation of I. edulis and local farmers were surveyed about their knowledge and uses ofInga. Results showed that additions of lime (Ca) significantly increased total number of nodules of I.edulis and there was a significant interaction effect between P and lime in terms of nodule biomass for I.edulis. In comparing G. sepium and I. edulis, P had a significant positive effect on nodule biomass andactivity and there was a significant interaction effect with species. The augur method cannot be used topredict nodulation values found with the trench method. All but three of 24 farmers interviewed cultivatedspecies of Inga, mainly for fruit and shade purposes.