, Volume 65, Issue 2, pp 191-200

Nitrous oxide and nitric oxide fluxes from an upland field in Japan: effect of urea type, placement, and crop residues

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Abstract

Fertilizer type and application mode may influence nitrous oxide(N2O) and nitric oxide (NO) emissions as well as crop yield. Using astatic chamber method, fluxes of both gases from a Chinese cabbage field inJapan were measured in situ following the application of easily decomposableurea by broadcasting (U-BC) and banding (U-B) and coated urea by banding(CU-B),respectively, at an application rate of 250 kg Nha−1. The measurements were made throughout the growingseason and continued 3 more months after harvest to determine the effect ofcropresidues on the emissions. Large N2O fluxes from U-BC occurredwithinabout 2 weeks after the application of the N fertilizer, while that from bothU-B and CU-B was prolonged by about 2 weeks, and significant emissions lasted alonger time but with a smaller emission size. Substantial N2O fluxesderived from crop residues were observed in the late growing season (especiallyfollowing rainfall) as well as after harvest, at all treatments including thecontrol plots (CK). Large NO fluxes occurred only at U-BC within the first 2weeks through the measurements. Total emissions were estimated to be 38.1,78.3,77.8, and 100.4 mg N2O-N m−2 and 0.7,194.9, 8.5, and 11.4 mg NO-N m−2 at CK, U-BC,U-B,and CU-B, respectively. Statistical analyses indicate that neither the bandmodenor the coated urea was able to significantly reduce the total N2Oemission through the season, but the band mode substantially reduced the NOemission. However, the application of urea by the band mode presented a 22.8%increase in crop yield as compared with urea applied by broadcasting.Therefore,by improving fertilizer use efficiency to decrease the amount of N needed tobetter meet the crop growing demand, the band mode may be a good agriculturalpractice to also reduce N2O emission. In addition, the experimentdemonstrated that crop residue is a large source of N2O emission.