长期定位有机物料还田对关中平原冬小麦-玉米轮作土壤N2O排放的影响

为定量研究有机物料还田对农田土壤N2O排放的影响,采用静态暗箱-气相色谱法对关中平原冬小麦-玉米轮作24 a长期定位施肥试验地土壤N2O排放速率和相关环境因子进行了周年观测,试验处理为对照(CK,0 kg·hm~(-2))、氮磷钾(NPK,353kg·hm~(-2))、氮磷钾加秸秆还田NPKS,(353+40)kg·hm~(-2)]和氮磷钾加牛粪NPKM,(238+115)kg·hm~(-2)]4个处理.结果表明观测期内,CK处理N2O排放速率较小2.9 g·(hm~2·d)~(-1)];施肥处理在冬小麦季施肥和玉米季灌溉后均出现排放峰,最高值分别为NPKS113.4 g·(hm~2·d)~(-1)]和NPKM495.0 g·(hm~2·d)~(-1)]处理.各处理N2O排放通量与土壤湿度均呈显著正相关关系(r0.28,P0.05).CK、NPK、NPKS和NPKM处理N2O年排放总量分别为(0.1±0.0)、(2.6±0.1)、(3.4±0.7)和(2.9±0.3)kg·hm~(-2),施肥处理排放总量显著高于CK处理(P0.05),但施肥处理之间差异不显著(P=0.06),说明施肥促进了N2O排放,但有机物料还田未能显著增加N2O排放.各施肥处理N2O直接排放系数分别为0.72%、0.83%和0.80%,均低于IPCC缺省值1%.施肥处理中,NPKM处理的单位产量N2O排放量最低.

Effects of Long-term Organic Amendments on Soil N2 O Emissions from Winter Wheat-maize Cropping Systems in the Guanzhong Plain

The primary aim of this study was to quantify the effects of long-term organic amendments on soil nitrous oxide (N₂O) emissions. Using static chamber-gas chromatograph technique, we measured N₂O fluxes from winter wheat-maize rotation system and related environmental factors in the Guanzhong Plain for one year (October 2014 to October 2015). Field experiments were based on the "Chinese National Loess Fertility and Fertilizer Effects Long-term Monitoring Experiment". Four treatments were control (CK, 0 kg·hm^-2), NPK (NPK, 353 kg·hm^-2), NPK combined with maize strawNPKS, (353+40) kg·hm^-2] and cattle wasteNPKM, (238+115) kg·hm^-2]. During the experimental period, N₂O fluxes from CK treatment were small<2.9 g·(hm²·d)^-1]; while emissions from fertilized treatments peaked after fertilizationup to 113.4 g·(hm²·d)^-1 for NPKS] and irrigationup to 495.0 g·(hm²·d)^-1 for NPKM] during winter wheat and maize seasons, respectively. N₂O flux was significantly correlated to soil water-filled pore space for all treatments (r>0.28,P<0.05). Annual N₂O emissions were (0.1±0.0), (2.6±0.1), (3.4±0.7) and (2.9±0.3) kg·hm^-2 for CK, NPK, NPKS and NPKM, respectively. The fertilized treatments released higher N₂O emissions than CK treatment (P<0.05), indicating that fertilization stimulated N₂O emissions. However, the differences in N₂O emissions were not significant among the fertilized treatments (P=0.06), suggesting that organic amendments did not increase N₂O emissions obviously. The direct emission factors were 0.72%, 0.83% and 0.80% for NPK, NPKS and NPKM, respectively, all of which were lower than the IPCC default of 1%. The yield-scaled N₂O emission for NPKM was the lowest among the fertilized treatments.