Effects of Reduced N Fertilizer Application on Greenhouse Gas Emissions from Wheat Fields in Huang-huai-hai Area

In order to investigate the effects of reduced nitrogen application on greenhouse emission from the wheat fields in Huang-huai-hai area, using static chamber-gas chromatograph technique, we explored the changes of greenhouse gases emissions and intensity from the wheat fields with the different N treatments:CK, a routine amount for farmers, 300 kg·N·hm^-2; N₁,270 kg·N·hm^-2; N₂, 240 kg·N·hm^-2;N₃, 210 kg·N·hm^-2 and N₄,180 kg·N·hm^-2. The results showed that the greenhouse gas fluxes had obvious seasonal changes with the different reduced rates of N fertilizer application. The effects of reduced N fertilizer application on the emissions of CO₂ and N₂O were significant while that of CH₄ was not significant. The cumulative emissions of CO₂ and N₂O were in the order of CK>N₁>N₂>N₄>N₃ and CK>N₁>N₂>N₃>N₄, respectively, with the significant difference among different treatments (p<0.05); and that of CH₄ was in the order of N₂>CK>N₄>N₃>N₁ without significant difference among different treatments (p>0.05).Compared with CK, the cumulative emissions of CO₂ with the treatments of N₁,N₂,N₃ and N4 was decreased by 4.9%,18.7%,36.5% and 31.2%,respectively; and the cumulative emissions of N₂O with the treatments of N₁,N₂,N₃ and N4 was decreased by 21.9%,32.5%,40.4% and 53.5%, respectively. There was a significant positive correlation between the amount of N fertilizer application and N₂O emissions(r=0.939,p<0.05).The effects of reduced N fertilizer application on the greenhouse gas intensity (GHGI) were also significant, and the GHGI was in the order of CK>N₁>N₂>N₄>N₃ with significant difference among treatments (p<0.05).Compared with CK, the GHGI with the treatments of N₁,N₂, N₃ and N4 was decreased by 7.7%,11.5%,34.6% and 19.2%, respectively. Wheat yield had no statistical significant difference with reduced N fertilizer rates. Therefore, the optimal rate of N fertilizer was 210 kg·N·hm^-2 economically and environmentally, with stable wheat yield and the lowest GHGI. The study would provide the basic data for the establishment of reasonable fertilization system in Huang-huai-hai area.