Are higher N2O emissions from soils under soybean that under other crops?.

COSENTINO, V. R. N.; MIGUEL A. TABOADA

Montevideo

Conferencia; 19th ISTRO Conference. IV reunión SUCS; 2012

Despite the National Greenhouse Gas (GHG) Inventory of Argentina shows nitrous oxide (N2O) to be the main emission source from agricultural soils, field measurements are almost inexistent in the country. This work reports field results on N2O emissions and their affecting factors from zero tilled loams (Typic Argiudolls). These soils were subjected to a ?wheat / soybean - maize ? soybean? rotation, in the subhumid Pampas region of Argentina (34 ° 57 ´29´´S, 60 ° 13´ 11´´W). In order to compare N2O emissions between soybean and non fixing N crops (wheat and maize) and their residues, three field lots were sampled five times from November 2009 through December 2010. N2O emissions only occurred between 14 and 24°C topsoil temperature, in which 0 - 314 g N2O-N*m2*h-1 rates were measured. N2O fluxes were positively correlated (R2 = 0.43) with nitrate (NO3-) content (0-20 cm). Comparing between crops at the same sampling dates, N2O emissions were higher in: a) V5 maize than in senescent wheat crop, because of higher NO3- concentration in recently fertilized corn; b) residues of double cropped soybean than those of in maize (p