02760naa a2200277 a 450000100080000000500110000800800410001910000230006024501280008326000090021152019620022065000160218265000200219865000290221865300200224770000190226770000190228670000180230570000210232370000110234470000200235570000200237570000180239570000170241377300520243021009592019-01-10       2018    bl uuuu     u00u1 u    #d1 aSANTANNA, S. A. C.  aBiological nitrogen fixation and soil N2O emissions from legume residues in an Acrisol in SE Brazil.h[electronic resource]  c2018  anformation is lacking concerning the contribution of green manure legumes to N2O emissionsfrom tropicalsoils.In a three-yearfield study, we measured the N accumulation and the N2fixation by three green manure legumesand the effects of their residues on N2O production from a tropical soil (Haplic Acrisol) under an organic farmingsystem. The legumes were jack bean (Canavalia ensiformisL.), velvet bean [Mucuna pruriens(L.) DC] and sunnhemp (Crotalaria junceaL.), which were mown atthe late pod-filling stage. The N accumulation in residues variedsubstantially among the legumetypes and the growing seasons(78?422 kg ha?1). The contribution of N2fixationto legume residues, expressed as the proportion of N in plant derived from air (%Ndfa), was relatively low in thefirst year (23?36%) and increased significantly in the following two years (46?85%). The highest amount of N2fixed was in the residues of jack bean, reaching 360 kg N ha?1. The residue of this legume and that of velvetbean caused the highest mean annual soil N2O emissions (3.78 and 3.29 kg N2O-N ha?1, respectively). Themean percentage of N lost as N2O derived from residues was not significantly affected by legume type, rangingfrom 0.58% (sunn hemp) to 0.72% (velvet bean). These percentages were below the default IPCC emission factorof 1% for N additions from plant residue or from synthetic fertilizers. We also showed that N in legume residuesderived from BNF offers an important environmental advantage over synthetic N fertilizers owing to the avoid-ance of GHG emissions (360?944 CO2-equivalent ha?1yr?1) during Haber-Bosch process and also during trans-portation and application in thefields. The three green manure legumes provided significant higher cash crop(squash) yield compared to maize, indicating the direct economic benefit of BNF for organic farming. Morefield studies are needed to assess the dynamics of gaseous N losses from plant residues in other tropical biomes.  aCover crops  aDenitrification  aGreenhouse gas emissions  aOrganic farming1 aMARTINS, M. R.1 aGOULART, J. B.1 aARAUJO, S. N.1 aARAUJO, E. da S.1 aZAMAN.1 aJANTALIA, C. P.1 aALVES, B. J. R.1 aBODDEY, R. M.1 aURQUIAGA, S.  tGeoderma Regionalgv.15, e00196, December 2018.