02637nam a2200253 a 450000100080000000500110000800800410001910000230006024501390008326001210022230000090034352018010035265000250215365000150217865000120219365000290220565000290223465000190226370000250228270000200230770000170232770000170234470000220236121634972024-04-11       2004    bl uuuu     u00u1 u    #d1 aCARVALHO, A. M. de  aNO and N2O emissions related to the nitrogen fertilization in a cornfield under No-tillage and tillage sistems.h[electronic resource]  aIn: CONFERÊNCIA CIENTÍFICA DO LBA, 3., 2004, Brasília, DF. Anais de trabalhos completos. Brasília, DF: LBAc2004  a1 p.  aThe dynamic of nitrogen oxides emissions from Cerrado soils related to the nitrogen fertilization is still not well known, in spite of the intensification of agricultural activities in this region. NO and N2O emissions were measured immediately and up to five days after nitrogen fertilization in a cornfield, under no-tillage and tillage systems, in the Cerrado region. The experiment was conduced at EMBRAPA-Cerrados (Planaltina-DF), mucuna-preta/corn succession on a Oxisol. Associated with irrigation, 20 kg ha-1 N (at the sowing) and 60 kg ha-1 N-urea (cover) were applied. The experimental design used was random blocks, in no-tillage and tillage systems. The fluxes were determined immediately, one, two, three and five days after nitrogen cover. In each plot, fluxes of NO and N2O were measured in four and three PVC chambers, respectively. Higher NO fluxes were found immediately (4 to 6 ng NO-N cm-2 h-1) and 3 days after N fertilization (3.5 to 5.5 ng NO-N cm-2 h-1). The lowest fluxes were found after five days (0.7 to 2.7 ng NO-N cm-2 h-1). In general, the no-tillage block showed higher fluxes soon after the N fertilization compared to the tillage block. On the other hand, the tillage blocks presented higher fluxes in the third day. Most of the N2O fluxes values were below the detection limit (0.6 ng ng N2O-N cm-2 h-1), except in the first and third day, when higher emissions (2.6 and 0.63 ng N2O-N cm-2 h-1) were measured observed in the no-tillage blocks. NO and N2O emissions were not correlated with air and soil temperature and soil moisture. The results suggest an immediate pulse in the NO emission after fertilization and irrigation, and a second pulse after three days. After five days, the fluxes were reduced to the background levels (around 1.2 ng NO-N cm-2 h-1).  aNitrogen fertilizers  aNo-tillage  aTillage  aFertilizante Nitrogenado  aFixação de Nitrogênio  aPlantio Direto1 aBUSTAMANTE, M. M. C.1 aKOZOVITS, A. R.1 aSOUSA, D. M.1 aVIANA, L. T.1 aMIRANDA, L. de M.