03386naa a2200265 a 450000100080000000500110000800800410001902400550006010000140011524501540012926000090028352025810029265000150287365000090288865300290289765300160292665300080294270000140295070000190296470000210298370000220300470000160302670000120304277300660305420308662016-02-12       2015    bl uuuu     u00u1 u    #d7 ahttp://dx.doi.org/10.1016/j.still.2014.10.0112DOI1 aBAYER, C.  aSoil nitrous oxide emissions as affected by long-term tillage, cropping systems and nitrogen fertilization in Southern Brazil.h[electronic resource]  c2015  aSoil 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 and subtropical soils. In an 18-yr old experiment located in a subtropical Acrisol of Southern Brazil we conducted a sequence of two trials. The 1-year trial (October 2003?2004) was set to evaluate the long-term effects of tillage [CT: conventional; and NT: no-tillage] and cropping systems [O/M: black oat (Avena strigosa Schreb.)/maize (Zea mays L.); and V/M: vetch (Vicia sativa L.)/maize] on soil N2O emissions, either in the post-management period (45 days after desiccation and knife-rolling of winter cover crops) or in the whole year. The second and short-term trial (October?November 2004) was carried out to compare the impact of N sources [urea (mineral) and legume-residue of vetch (biologically fixed), both at 180 kg N ha?1] on soil N2O emissions during 53 days after cover-crop management. Air sampling was carried out by static chambers and N2O analysis by gas chromatography. In the 45-day post-management period of the 1-year trial, soil N2O emissions were practically not affected by tillage systems, but increased 4 times due to vetch residues (average of 0.40 ± 0.08 kg N ha?1 in V/M versus 0.10 ± 0.05 kg N ha?1 in O/M) and related with soil contents of NO3?-N, NH4+-N, and dissolved organic C (DOC). Over the whole year, soil N2O emissions under CT were similar for grass- and legume-based cropping systems and averaged 0.43 ± 0.17 kg N ha?1, while NT exacerbated N2O emissions in the legume-based cropping system (0.80 ± 0.07 kg N ha?1 in V/M versus ?0.07 ± 0.06 kg N ha?1 in O/M). Maize yield was not affected by tillage, but increased from 2.32 Mg ha?1 in O/M to 4.44 Mg ha?1 in V/M. Yield-scaled N2O emissions varied from ?33 g N2O-N Mg?1 grain in NT O/M to 179 g N2O-N Mg?1 grain in NT V/M, and were intermediate in CT soil (106 and 156 g N2O-N Mg?1grain in V/M and O/M cropping systems, respectively). In the short-term trial, the N2O emitted in excess relative to the control treatment (O/M without N fertilizer) was at least 3 times greater with urea-N (0.44% of applied N) than with legume-residue-Nsource (0.13% of applied N). Yield-scaled N2O emission after vetch residues management (67 g N Mg?1 grain) was half of that after urea-N application (152 g N Mg?1 grain). Partially supplying the maize N requirements with winter legume cover-crops may be a feasible strategy to mitigate soil N2O emissions in the subtropical conservation agriculture.  ano-tillage  aurea  aConservation agriculture  aCover-crops  aN2O1 aGOMES, J.1 aZANATTA, J. A.1 aVIEIRA, F. C. B.1 aPICCOLO, M. de C.1 aDIECKOW, J.1 aSIX, J.  tSoil & Tillage Research, Amsterdamgv. 146, p. 213-222, 2015.