施肥方式对冬小麦季紫色土N2O排放特征的影响

Effects of fertilizer application regimes on soil N2O emissions in the croplands of purple soil in the Sichuan Basin during wheat season

  • 摘要: 利用紫色土养分循环长期定位施肥试验平台, 通过静态箱?气相色谱法, 于2012年11月至2013年5月, 研究了单施氮肥(N)、猪厩肥(OM)、常规氮磷钾肥(NPK)、猪厩肥配施氮磷钾肥(OMNPK)、秸秆还田配施氮磷钾肥(CRNPK)及对照不施肥(NF)6种施肥方式下, 紫色土冬小麦季土壤N2O的排放特征。结果表明, 在相同施氮水平130 kg(N)·hm-2下, 施肥方式对N2O排放量有显著影响(P<0.05)。N、OM、NPK、OMNPK和CRNPK处理下, 土壤N2O排放量kg(N)·hm-2分别为0.38、0.36、0.29、0.33和0.19, N2O排放系数分别为0.25%、0.23%、0.18%、0.21%和0.10%。NF的土壤N2O排放量为0.06 kg(N)·hm-2。土壤无机氮含量(NO3--N和NH44-N)是N2O排放的主要影响因子, 降雨能有效激发N2O排放。基于小麦产量评价不同施肥方式下的N2O排放, 结果表明, N、OM、NPK、OMNPK和CRNPK单位小麦产量N2O的GWP值yield-scaled GWP, kg(CO2 eq)·t-1分别为132.57、45.70、49.07、48.92和26.41。CRNPK的小麦产量与6种施肥方式中获得最大产量的OM间没有显著差异, 但显著高于其他处理。而且, CRNPK的yield-scaled GWP比紫色土地区冬小麦种植中常规施肥方式(NPK)显著减少46%, 并显著低于其他4种施肥方式。可见, 秸秆还田配施氮磷钾肥在保证小麦产量的同时, 能有效减少因施肥引发的N2O排放, 可作为紫色土地区推荐的最佳施肥措施。

     

    Abstract: Nitrous oxide (N2O) was undoubtedly a key element with respect to global warming and climate change. As about 60% of global anthropogenic N2O emissions have originated from agricultural soils, it has been a huge challenge to maintain high crop yields while reducing N2O emissions under the continued application of nitrogen fertilizers. Limited available field data have explored the effects of fertilizer application regimes on soil N2O emissions in the Sichuan Basin, one of the most intensive agricultural regions in China. Thus the objective of this research was to compare the effects of different N fertilizer application regimes on soil N2O emissions so as to find the best N fertilizer management practice which not only decreased N2O emission, but also maintained high crop yields. Static chamber-gas chromatographic techniques were used to measure soil N2O emissions from purple soil croplands with long-term N fertilization in treatments of pure synthetic N fertilizer (N), pig manure (OM), synthetic NPK fertilizer (NPK), pig manure combined with synthetic NPK fertilizer (OMNPK) and returned crop residues combined with synthetic NPK fertilizer (CRNPK). No fertilizer was applied under the control experiment (NF). The in situ field measurements were conducted during wheat season from November 2012 to May 2013. The results showed that cumulative N2O fluxes in different fertilization regimes were significantly different (P < 0.05) even when the same rates of total N were applied 130 kg(N)·hm-2. Cumulative N2O fluxes in treatments of N, OM, NPK, OMNPK and CRNPK were 0.38 kg(N)·hm-2, 0.36 kg(N)·hm-2, 0.29 kg(N)·hm-2, 0.33 kg(N)·hm-2 and 0.19 kg(N)·hm-2, respectively. N2O emission factors in the respective treatments were 0.25%, 0.23%, 0.18%, 0.21% and 0.10%. Cumulative N2O flux in treatment of NF was 0.06 kg(N)·hm?2. Nitrogen fertilizer application significantly enhanced N2O emission. Inorganic N (ammonium and nitrate) content was the main controlling factor of soil N2O emission. Also rainfall significantly enhanced soil N2O emission. Wheat grain yields in treatments of N, OM, NPK, OMNPK and CRNPK were 1.34 t·hm-2, 3.71 t·hm-2, 2.80 t·hm-2, 3.13 t·hm-2 and 3.40 t·hm-2, respectively. Wheat grain yield in CRNPK treatment was not significantly different from that of OM treatment, which had the maximal yield that was much higher than yields of all the other treatments (P < 0.05). Furthermore, we assessed the global warm potential (GWP) of soil N2O emission on the basis of crop grain yield under the different treatments. The results showed that the yield-based GWPs of treatments of N, OM, NPK, OMNPK and CRNPK were 132.57 kg(CO2 eq)·t-1, 45.70 kg(CO2 eq)·t-1, 49.07 kg(CO2 eq)·t-1, 48.92 kg(CO2 eq)·t-1 and 26.41 kg(CO2 eq)·t-1, respectively. The yield-based GWP of soil N2O emissions in CRNPK treatment was the lowest of all the treatments. In contrast with conventional fertilization regime (NPK), the yield-based GWP decreased by 46%. This implied that returned crop residues combined with synthetic NPK fertilizer not only increased grain yield, but also decreased soil N2O emission due to the application of N fertilizer. For wheat season, the fertilizer application regime of returned crop residues with reduced synthetic fertilizer was therefore recommended as the best fertilization measure in purple soil croplands.

     

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