减氮及不同肥料配施对稻田CH_4和N_2O排放的影响

Effects of reduced nitrogen and combined application of different fertilizers on CH_4 and N_2O emissions in paddy fields

为比较不同施肥处理的温室气体减排效果,采用田间试验研究了7种肥料处理包括减氮增钾(N190CF+U+K)、减氮追施脲铵(N230CF+UA)、配方施肥(N230CF+U)、有机无机配施(N230O_(F+U))、稳定性复合肥(N230_(UHD))、脲甲醛(N230_(UF))和常规施肥(N270_(CF+U))条件下稻田CH_4和N_2O的排放特及主要环境驱动因子变化.结果表明:不同施肥处理CH_4排放总量范围为78.61~181.96kg/hm^2,除N230_(UHD)处理外,其他施肥处理较N270_(CF+U)减排CH4_达32.0%~49.6%,以N230_(CF+UA_处理减排效果最好;各施肥处理N_2O累积排放量为0.28~0.46kg/hm^2,除N230_(CF+UA)处理外,其他施肥处理减少N_2O排放15.4%~38.6%,以N230_(OF+U)最佳.此外,稻田N_2O排放与田面水中NH_4^+-N和NO_3^--N含量呈显著性正相关(P<0.05),CH_4排放与水深以及土壤温度均呈现极显著正相关性(P<0.01),而与土壤NH_4+^-N呈显著负相关(P<0.05).进一步计算100a尺度下CH_4和N_2O的增温潜势(GWP)和温室气体排放强度(GHGI)可知,除N230_(UHD)处理外,其他施肥处理GWP均低于常规施肥处理,减排效果达32.2%~47.9%;N230_(CF+UA)、N230_(OF+U)、N190_(CF+U+K)以及N230_(UF)处理均能实现稳产减排,其中以N230_(CF+UA)和N230_(OF+U)处理GHGI较低,GHGI减少比例高达40%以上.

Nitrogen source and fertilizing rate are the important factors that affecting greenhouse gas emissions from cropland.In order to evaluate the potential of reduced nitrogen and combined application of different types of fertilizer to mitigate CH4and N2O emissions,a field experiment was conducted to investigate CH4and N2O emissions from paddy field and the relevant driving factors.Seven fertilizer treatments were applied in this experiment,including reduced nitrogen combined with increased potassium treatment(N190CF+U+K),reduced nitrogen plus topdressing urea ammonium treatment(N230CF+UA),formula fertilization treatment(N230CF+U),combined application of organic-inorganic fertilizer(N230OF+U),stability urea with dicyandiamide and hydroquinone treatment(N230UHD),urea formaldehyde treatment(N230UF)and conventional fertilization treatment(N270CF+U).The results showed that cumulative CH4emissions from different fertilizer treatments ranged from78.61~181.96kg/hm2.All fertilizer treatments except for N230UHD reduced CH4emissions by32.0%~49.6%relative to the N270CF+U treatment.The reduced nitrogen plus topdressing urea ammonium treatment had the best CH4mitigation effect among all fertilizer treatments.Cumulative N2O emissions from the paddy field ranged from0.28~0.46kg/hm2.With the exception of N230CF+UA,total N2O emissions for all fertilizer treatments were decreased by15.4%~38.6%in comparison with conventional fertilization treatment.The combined application of organic-inorganic fertilizer showed the priority among all fertilizer treatments.Moreover,N2O emissions in paddy field were positively correlated only with the NH4+-N and NO3--N concentrations of field surface water(P<0.05).However,CH4emissions were significantly and positively correlated with water depth and soil temperature(P<0.01),while being negatively correlated with NH4+-N value of topsoil(P<0.05).The aggregate emission of N2O and CH4in the CO2equivalent(GWP)for the100-year horizon of each treatment and greenhouse gas intensity(GHGI,defined as yield scaled GWP at the100-year horizon)were also calculated.The N230UHD treatment increased GWP in the100-year horizon,while the other treatments decreased the GWP,with a32.2%reduction for N230UF,a34.9%reduction for N230CF+U,a37.2%reduction for N230OF+U,a37.7%reduction for N190CF+U+K,a47.9%reduction for N230CF+UA compared to N270CF+U.The N230CF+UA,N230OF+U,N230UF and N190CF+U+K treatments performed the best in reducing GHGI,and particularly the N230CF+UA and N230OF+U treatments decreased GHGI by more than40%,may be the better agricultural practice for both trace gas mitigation and increasing crop yields.