Soil nitrous oxide emissions as affected by long-term tillage, cropping systems and nitrogen fertilization in Southern Brazil

摘要: Abstract Soil nitrous oxide (N2O) emissions are affected by management practices, but little information is available on the interactive effects of tillage, cropping systems and N sources in tropical subtropical soils. In an 18-yr old experiment located a Acrisol Southern Brazil we conducted sequence two trials. The 1-year trial (October 2003–2004) was set to evaluate long-term tillage [CT: conventional; NT: no-tillage] [O/M: black oat (Avena strigosa Schreb.)/maize (Zea mays L.); V/M: vetch (Vicia sativa L.)/maize] soil N2O emissions, either post-management period (45 days after desiccation knife-rolling winter cover crops) or whole year. second short-term (October–November 2004) carried out compare impact [urea (mineral) legume-residue (biologically fixed), both at 180 kg N ha−1] during 53 cover-crop management. Air sampling static chambers analysis gas chromatography. 45-day trial, were practically not systems, increased 4 times due residues (average 0.40 ± 0.08 kg N ha−1 V/M versus 0.10 ± 0.05 kg N ha−1 O/M) related with contents NO3−-N, NH4+-N, dissolved organic C (DOC). Over year, under CT similar for grass- legume-based averaged 0.43 ± 0.17 kg N ha−1, while NT exacerbated system (0.80 ± 0.07 kg N ha−1 −0.07 ± 0.06 kg N ha−1 O/M). Maize yield from 2.32 Mg ha−1 O/M 4.44 Mg ha−1 V/M. Yield-scaled varied −33 g N2O-N Mg−1 grain 179 g V/M, intermediate (106 156 g N2O-N Mg−1grain respectively). emitted excess relative control treatment (O/M without fertilizer) least 3 greater urea-N (0.44% applied N) than legume-residue-Nsource (0.13% N). emission (67 g N Mg−1 grain) half that application (152 g N Mg−1 grain). Partially supplying maize requirements legume cover-crops may be feasible strategy mitigate conservation agriculture.