灌溉方式对设施土壤温室气体排放的影响

为了寻求在高产、高效、节水的同时能够最大程度促进温室气体减排的灌溉方式,以长期定位灌溉设施蔬菜(以番茄为例)栽培土壤为研究对象,探讨覆膜滴灌、节点式渗灌、沟灌3种不同灌溉方式对土壤温室气体(N₂O、CO₂、CH₄)排放特征的影响,以及温室气体排放与土壤温度和湿度两大环境因子的相关性,并运用产气比概念对温室气体累积排放量进行比较.结果表明:①在番茄生长季,不同灌溉方式下N₂O排放总量表现为沟灌(25.33 kg/hm2)>覆膜滴灌(23.87 kg/hm2)>节点式渗灌(10.04 kg/hm2),土壤温度适宜条件下,N₂O排放通量与土壤湿度呈极显著相关(P<0.01).②CO₂排放通量随着气温升高及植株生长而逐渐增大,具有明显的季节性变化.不同灌溉方式下CO₂排放总量表现为节点式渗灌(11.84 t/hm2)>沟灌(10.45 t/hm2)>覆膜滴灌(9.53 t/hm2)；覆膜滴灌和节点式渗灌处理下CO₂排放通量与土壤温度呈极显著相关(P<0.01),沟灌处理下二者呈显著相关(P<0.05).③在番茄整个生长季期间,土壤总体表现为大气CH₄的汇,不同灌溉方式下CH₄吸收总量表现为节点式渗灌(1.98 kg/hm2)>覆膜滴灌(0.93 kg/hm2)>沟灌(0.71 kg/hm2),CH₄排放通量与土壤湿度呈显著相关(P<0.05).研究显示,采用覆膜滴灌方式不仅可以达到高产、高效、节水的目标,而且综合排放的温室气体量最少,可达到土壤温室气体最大程度的减排效果,减缓全球气候变暖趋势,是一种最佳的灌溉方式. 

Effects of Irrigation Methods on Emissions of Greenhouse Gases from Facilities Soil

Long-term cultivated soil(tomato) was selected as the research object to seek high yield, high efficiency and water-saving irrigation methods while minimizing greenhouse gas emissions as much as possible. Three irrigation methods(mulched drip irrigation, drip filtration irrigation and furrow irrigation) were investigated for soil greenhouse gas(N₂O, CO₂ and CH₄) emission characteristics, in order to reveal the relationship between greenhouse gases and soil temperature(5 cm) and moisture. Based on the research results, we put forward the concept of ′yield gas ratio′ to compare the cumulative emissions of greenhouse gases. The results showed that: (1) the total N₂O emissions during the tomato growing season decreased with the order of furrow irrigation(25.33 kg/hm2) > mulched drip irrigation(23.87 kg/hm2) > drip filtration irrigation(10.04 kg/hm2). When soil temperature was appropriate, N₂O emission flux was extremely significantly correlated with soil moisture(P<0.01). (2) CO₂ emissions increased with increased temperature and plant growth. The CO₂ total emissions decreased with an order of drip filtration irrigation(11.84 t/hm2) > furrow irrigation(10.45 t/hm2) > mulched drip irrigation(9.53 t/hm2). The CO₂ emission fluxes of mulched drip irrigation and drip filtration irrigation were extremely significantly correlated with soil temperature(P<0.01), and the furrow irrigation was also significantly correlated with soil temperature(P<0.05). (3) Overall, CH₄ was a sink during the tomato growing season. The CH₄ total absorptions decreased with an order of drip filtration irrigation(1.98 kg/hm2) > mulched drip irrigation(0.93 kg/hm2) > furrow irrigation(0.71 kg/hm2), and CH₄ emission flux had significant correlation with soil moisture. In summary, using plastic mulched drip irrigation can not only realize goals of high yield, high efficiency and water conservation, but also achieves the least amount of greenhouse gas emissions. Besides, it attains the greatest degree of soil greenhouse gas emission reductions and can slow global warming. In conclusion, the plastic mulched drip irrigation is the best method of irrigation.