03384naa a2200289 a 450000100080000000500110000800800410001910000140006024501250007426000090019952025810020865000090278965000120279865000130281065300220282365300190284565300200286470000160288470000140290070000230291470000160293770000190295370000150297270000190298770000180300677300700302419995942014-11-10       2014    bl uuuu     u00u1 u    #d1 aSORDI, A.  aNitrous oxide emission factors for urine and dung patches in a subtropical Brazilian pastureland.h[electronic resource]  c2014  atCattle urine and dung (faeces) patches are nitrous oxide (N2O) sources in pasturelands with impactsin the global N2O budget, but specific information about those emissions are still missing for Braziliansubtropical and tropical regions. We conducted a sequence of 3 field-trials (summer, winter and spring,90 days each) to evaluate the N2O emission and emission factor (EF) after the deposition of 3 volumes ofcattle urine or 3 weights of dung (½, 1 and 1½ time the mean urination volume or defecation weight ofFriesian cows) on a free-drained Cambisol of a subtropical pastureland of Brazil. The N2O emission peaks(3198 g N2O-N m−2h−1after urine in summer was the highest) occurred on average 17 ± 9 days afterapplication (DAA), both for urine and dung, and dropped to the background levels 41 ± 10 DAA of urineand 49 ± 10 DAA of dung. The highest contents of NH4+-N in soil (200?250 mg N kg−1) occurred one dayafter urine application and 10?14 days later for dung (100?200 mg N kg−1). Nitrate peaks occurred from23 to 26 DAA in urine patches (∼40?50 mg N kg−1) and 19?50 DAA in dung patches (∼40?50 mg N kg−1).The N2O emission peaks for urine coincided with soil NH4+-N peak in winter but with soil NO3−-N peakin spring. For dung, the emission peak seemed to be more associated with soil NO3−-N than to NH4+-N,either in winter or spring (inorganic-N was not assessed in summer). It was not possible to concludewhether nitrification or denitrification was the dominant process in N2O production, but it seemed thatboth played relevant roles. The EF for urine, averaged across the seasons, diminished with increments inurine volume, from 0.33% in ½ volume to 0.19% in 1½ volume, possibly because urine percolated deeperinto the soil and proportionally less N remained available for N2O production in the top layer. The EFfor dung was 0.19%, 0.12% and 0.14% for ½, 1 and 1½ weight, respectively, showing no clear trend withincrement in dung weight. The lowest EFs for urine and dung occurred in winter, possibly because oflowest temperatures and soil water-filled pore space. The average EF for dung (0.15%) was lower thanthat of urine (0.26%), because urea-N of urine is more readily available for the hydrolysis than organicN forms of dung. This result suggests that these two excreta should be addressed separately in nationalgreenhouse gases inventories or communications. Our results suggest that the default 2% EF proposed inIPCC Guidelines for cattle excreta are overestimated for subtropical Brazil.  aGado  aNitrato  aPastagem  aFator de emissão  aÓxido nitroso  aVolume de urina1 aDIECKOW, J.1 aBAYER, C.1 aALBUQUERQUE, M. A.1 aPIVA, J. T.1 aZANATTA, J. A.1 aTOMAZI, M.1 aROSA, C. M. da1 aMORAES, A. de  tAgriculture, Ecosystems and Environmentgv. 190, p. 94-103, 2014.