轮作方式对冬水田温室气体排放的影响

以位于西南大学农业部重庆紫色土生态环境重点野外科学观测试验站内的冬水田(RF)、水稻-油菜轮作(RR)和水稻-儿菜轮作(RV)农田为研究对象,采用静态箱-气相色谱法对农田的温室气体的排放通量进行了为期一年的原位观测,其中采用静态暗箱技术观测CH4和N2O,静态明箱技术观测CO2.结果表明,不同轮作方式下CH4的年排放总量以CH4计,kg·hm-2]RF(422.87±27.1) RR(132.05±23.11) RV(50.91±3.83),其中RV与RR处理较RF处理CH4排放量有明显下降(P0.05);N2O的年排放总量以N2O计,kg·hm-2]依次为RV(21.38±6.51) RR(20.02±5.23) RF(0.48±0.02),RV和RR处理N2O的排放总量均显著高于RF(P0.05);CO2的年净排放总量以CO2计,t·hm-2]为RR(-55.43±5.04) RV(-29.1±3.00) RF(-14.08±1.81),RV和RR处理CO2的吸收量显著高于RF处理(P0.05).在100a时间尺度上,全年排放的CH4、N2O和CO2所引起综合GWP(以CO2计,t·hm-2)为RR(-46.43) RV(-22.01) RF(-2.11),表明冬水田转变为水旱轮作系统后能显著提升农田生态系统的增汇效果,相比于RV处理,RR处理增汇效果更好,即在西南地区水稻-油菜轮作农田在生态系统增汇上是一种最有效的轮作方式.

Effects of the Crop Rotation on Greenhouse Gases from Flooded Paddy Fields

A field experiment was conducted at the Key Field Station for Monitoring Eco-environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University, Chongqing. The static chamber and gas chromatography method was used to study the effect of the cropping systems on greenhouse gases from rice-fallow (RF), rice-rapeseed rotation (RR), and rice-brussel mustard rotation (RV) cropland in situ for a year. An opaque chamber was used for CH₄ and N₂O observations and a transparent chamber was utilized for CO₂ observations. The results show that the annual cumulative CH₄ emissions from different crop rotations were (CH₄, kg·hm^-2) RF (422.87±27.1) > RR (132.05±23.11) > RV (50.91±3.83). The RV and RR were significantly lower than RF (P<0.05). The annual cumulative emissions of N₂ON₂O, kg·hm^-2] were RV (21.38±6.51) > RR (20.02±5.23) > RF (0.48±0.02). The RV and RR were significantly higher than RF (P<0.05). The annual net cumulative emissions of CO₂ were (CO₂, t·hm^-2) RR (-55.43±5.04) > RV (-29.1±3.00) > RF (-14.08±1.81). The RV and RR were significantly higher than RF (P<0.05). At the time scale of 100 a, the integrated global warming potentials (GWP) of CH₄, N₂O, and CO₂ were (CO₂, t·hm^-2)RR(-46.43) > RV(-22.01) > RF(-2.11), indicating that converting flooded paddy fields to paddy-upland crop rotation systems notably increases the potential increment of carbon sinks. Compared with RV, RR has a better effect, which suggests that rice-rapeseed rotation is the most effective measure for the escalation of carbon sinks of ecosystems in the southwestern area.