秸秆还田对冬小麦-夏玉米农田土壤固碳、氧化亚氮排放和全球增温潜势的影响

旱地农田温室气体净排放(以全球增温潜势表示)主要取决于土壤固碳速率和氧化亚氮(N2O)排放量.基于长期定位施肥试验,综合分析2010～2017年表层(0～20 cm)土壤有机碳含量和2014～2017年N2O排放通量的观测结果,定量评价秸秆还田对关中平原冬小麦-夏玉米农田土壤固碳速率、N2O年排放量和全球增温潜势的影响...

Effects of Stalk Incorporation on Soil Carbon Sequestration, Nitrous Oxide Emissions, and Global Warming Potential of a Winter Wheat-Summer Maize Field in Guanzhong Plain

The net greenhouse gas emissions from upland soils, as indicated by global warming potential (GWP), mainly depend on the soil carbon sequestration and nitrous oxide (N₂O) emissions. The annual changes in surface (0-20 cm) soil organic carbon (SOC) content from 2010 to 2017 and the N₂O emissions from 2014 to 2017 were measured within a long-term fertilization experiment. The objective was to quantify the effect of stalk incorporation on the soil carbon sequestration, annual N₂O emissions, and GWP of a winter wheat-summer maize field in the Guanzhong Plain. The field experiment included three treatments:conventional fertilization (CF), conventional fertilization plus maize stalks (CFS), and an unfertilized control (CK). The CF and CFS treatments received the same amount of urea per year, with nitrogen (N) input at 165 kg·hm^-2 and 188 kg·hm^-2 in the winter wheat season and summer maize season, respectively. The CF treatment retained the stubbles (about 10 cm above ground) when harvesting the winter wheat and summer maize crops. The CFS treatment retained the same wheat stubbles and all maize stalks (containing approximately 40 kg·hm^-2 of N). The CK treatment was unfertilized throughout the year, with the stubble management the same as that in the CF treatment. The results showed that the CK treatment displayed few changes in SOC content and low N₂O emissions, with GWP varying from 0.04 to 0.11 t·(hm²·a)^-1. The SOC contents in the CF and CFS treatments increased linearly with the fertilization years (P<0.001), and their SOC sequestration rates were 0.69 t·(hm²·a)^-1 and 0.97 t·(hm²·a)^-1, respectively. The N₂O emissions from the CF and CFS treatments varied from 1.65 to 5.36 kg·(hm²·a)^-1 and from 3.08 to 7.73 kg·(hm²·a)^-1, respectively. The annual N₂O emissions from the CFS treatment were 43%-94% higher than those from the CF treatment, whereas the difference was only significant between 2015 and 2016 (P<0.05). The GWP of the CF and CFS treatments varied from -1.95 to -0.28 t·(hm²·a)^-1 and from -2.59 to -0.35 t·(hm²·a)^-1, respectively. The cumulative GWP of the CFS treatment was 42% lower than that of the CF treatment between 2014 and 2017. In summary, the studied winter wheat-summer maize field acted as a sink of greenhouse gases under the conventional fertilization regime. The stalk incorporation further favored greenhouse gas mitigation despite the trade-offs between SOC sequestration and N₂O emissions.