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

Green mulch applications affect mineral nitrogen beneath cupuaçu treesCarol M. Schwendener 1 , Erick C. Fernandes 1 , Johannes Lehmann 1 , MarcoRondon 2 , Elisa Wandelli 31 Department of Soil and Crop Sciences, Cornell University, Ithaca, NY2 International Center for Tropical Agriculture (CIAT), Cali, Colombia3 EMBRAPA, Amazonas-OccidentalCorresponding AuthorCarol M. Schwendener610 Bradfield HallDepartment of Soil and Crop SciencesCornell UniversityIthaca, NY 14853(607) 254-1244cms67@cornell.eduErick Fernandes (ecm3@cornell.edu)Johannes Lehmann (cl273@cornell.edu)Marco Rondon (m.rondon@cgiar.org)Elisa Wandelli (elisa@cpaa.embrapa.br)Cupuaçu (Theobroma grandiflorum) is an economically important crop and themost utilized fruit species in agroforestry systems in the Amazonas state ofBrazil. It is often produced on degraded soils and has a shallow root system andlow quality litter that perpetuate the low nutrient status of the soil. The applicationof high quality gliricidia (Gliricidia sepium) and inga (Inga edulis) prunings couldincrease decomposition rates of cupuaçu litter and improve soil nitrogen (N)availability beneath cupuaçu. Our objectives are to compare the effect of gliricidiaand inga leaf applications to cupuaçu litter on decomposition and N availability inthe soil and to determine if interactions occur between litter species duringdecomposition and nutrient release. In a greenhouse experiment, dried gliricidiaand a gliricidia/inga combination were mixed with cupuaçu litter and applied to adegraded Oxisol. Mineral soil N, carbon (C) and macronutrients in the soil andlitter, and litter decomposition were analyzed at 7, 29, 50, 98, and 162 days afterlitter application. Mineral N accumulation in the soil corresponded positively tothe amount of gliricidia present in the litter, however the litter decomposition raterelated only to the presence or absence of gliricidia. Additions of legumebiomass were additive to N release rates of cupuaçu litter. Further studies willtest for immobilization of nutrients by cupuaçu litter and increases in cupuaçulitter decomposition rates in the presence of gliricidia. An understanding of theseinteractions will facilitate development of green mulch application ratesappropriate for cupuaçu trees.