Gross Nitrogen Transformation Rates Do Not Support Previously Described BNI Capacities of Selected Brachiaria Genotypes
Eduardo Vazquez1, Nikola Teutscherová2, Mirjam Pulleman3, Michael Dannenmann4, Klaus Butterbach-Bahl4, Paul Töchterle4, Jacobo Arango5
1Universidad Politécnica de Madrid, Dept. of Agricultural Production, Spain
Nitrification is one of the key processes leading water contamination and greenhouse gas emissions in the form of N2O in pasture systems. As vast areas of tropical pastures are considered nitrogen (N) limited, grasses from the Brachiaria genus have adapted to reduce N losses and increase N use efficiency by releasing substances capable of biological nitrification inhibition (BNI) in the rhizosphere. Although the release of BNI compounds and its impact on N2O emissions and net nitrification rates in soil have been studied, the impact of BNI on gross nitrogen transformation rates have not been addressed, despite its relevance to mechanistic understanding of this phenomena. Using intact soil cores and 15N dilution technique we evaluated gross N transformation rates in five Brachiaria genotypes, including high (CIAT-679, CIAT-16888 and Bh08-1149) and low BNI (Mulato hybrid and CIAT-26146) accessions. Two experimental plots, one established 14 and one 5 years ago were used, located in areas with contrasting soil types of Colombia.
Keywords: N immobilisation, N mineralisation, nitrification, tropical grassland
Contact Address: Eduardo Vazquez, Universidad Politécnica de Madrid, Dept. of Agricultural Production, Av. Puerta de Hierro, 2, 28040 Madrid, Spain, e-mail: eduardo.vazquezupm.es