Abstract ID: 531

CO2, NO AND N2O EMISSIONS FROM SOILS TO THE ATMOSPHERE UNDER DIFFERENT CROPPING SYSTEMS IN THE CERRADO REGION

The Cerrado Region in Central Brazil has been focus of intense agricultural expansion since the 1970s. The expansion was accompanied by intensive use of fertilizer, irrigation and management practices. Here, we present data on CO2, NO and N2O emissions from Oxisols under no-till cropping systems in the Cerrado (maize-Brachiaria-irrigated bean rotation, soybean monoculture and non irrigated cotton). In non-irrigated crops, fertilization with N induced predominantly NO-N fluxes. NO-N fluxes increased from 3.9 to 8,8 ng NO-N cm-2 h-1 (maize), to 83.3 ng NO-N cm-2 h-1 (cotton, inter-rows) and to 39.3 ng NO-N cm-2 h-1 (cotton, rows). During soybean cultivation, NO-N fluxes were similar to those from native cerrado. Fertilization with-N associated with irrigation (bean), increased both NO-N and N2O-N. NO-N flux was 5.0 ng NO-N cm-2 h-1 and N2O-N was 2.3 ng N2O-N cm-2 h-1, and after the subsequent N-addition fluxes were even higher (12.2 ng NO-N cm-2 h-1 and 10.6 ng N2O-N cm-2 h-1). Pulses of N2O-N were measured during the senescence of irrigated bean (1.7 ng N2O-N cm-2 h-1), soybean (3.8 ng N2O-N cm-2 h-1) and cotton (1.6 ng N2O-N cm-2 h-1). Fertilizer-induced emission factors estimated for NO-N were 0.1% (maize), 0.2% (irrigated bean) and 0.4% (cotton) while for N2O-N were 0.3% (maize), 0.2% (irrigated bean) and 0.2% (cotton). Comparing with an area under native cerrado vegetation, soil respiration was higher under irrigated bean (1.8 umol CO2-C m-2 s-1), lower under cotton (2.3 umol CO2-C m-2 s-1) and similar under soybean and maize (1.8 umol CO2-C m-2 s-1).

Session:  Biogeochemistry - Sources, sinks, and atmospheric chemistry of trace gases.

Presentation Type:  Poster