秸秆与化肥减量配施对菜地土壤温室气体排放的影响

Effect of Straw Residues in Combination with Reduced Fertilization Rate on Greenhouse Gas Emissions from a Vegetable Field

采用静态箱/气相色谱法,2016年11月至2017年9月通过田间原位试验,设置了无物料还田(CK)、常规化肥(F)、秸秆还田配施100%化肥(100FS)、秸秆还田配施70%化肥(70FS)、秸秆还田配施60%化肥(60FS)、秸秆还田配施50%化肥(50FS),对比分析了在化肥减量的基础上,配施秸秆处理的菜地(莴笋-卷心菜-辣椒轮作)土壤CO_2、CH_4、N_2O动态变化特征及温室效应,研究秸秆与化肥减量配施对菜地温室气体排放的影响.结果表明,土壤CO_2、CH_4、N_2O排放具有一定的季节变化规律,排放高峰主要集中在4~8月,且在施肥灌水后均会出现气体的排放峰.秸秆与化肥配施较常规施肥(F)处理提高了土壤N_2O排放量,累积排放量及其排放系数,其中100FS处理的效果最为明显,辣椒季的累积排放通量明显高于莴笋季和卷心菜季,高达60.76 kg·hm^(-2)(P<0.05),N_2O的排放系数(以N_2O-N/N计)为0.138 kg·kg-1,而秸秆与化肥减量配施较100FS处理可以降低氮肥的N_2O排放系数.与对照CK和F处理相比,70FS处理降低了土壤CO_2排放量和累积排放量,分别为55.28~1 831.62 mg·(m2·h)-1和7 502.13~25 988.55 kg·hm^(-2),而其他秸秆与化肥配施处理均增加了CO_2累积排放通量,尤其是60FS和50FS处理.对土壤CH_4排放而言,辣椒季的排放波动较大,除CK外,各处理的土壤CH_4累积排放量多为负值,表现为大气中CH_4汇;秸秆与化肥减量30%~50%配施处理均降低了辣椒季的土壤CH_4排放量和累积排放通量,而100FS处理提高了CH_4排放量和累积排放通量.与CK和F处理相比,除70FS外,100FS、60FS和50FS均显著提高了GWP.总体上,从温室气体排放角度,在常规化肥施用的基础上减量30%再与秸秆配施可以降低土壤CO_2和CH_4排放,缓解温室气体的增温潜势,而对土壤N_2O减排效果不显著.

Greenhouse gases mainly come from farmland soils. Re-spreading chaff（ straw returning） is an effective ecological management in China. Quantitative analysis of straw residues together with reduced fertilization rates can provide a scientific basis for reducing greenhouse gas emissions. A field experiment with six different fertilizer amounts combined with straw residues was carried out in a vegetable field（ lettuce-cabbage-chili rotation）,including the control（ CK）,conventional fertilizing（ F）,straw returning with100% conventional fertilizing（ 100 FS）,straw returning with 70% conventional fertilizing（ 70 FS）,straw returning with 60%conventional fertilizing（ 60 FS）,and straw returning with 50% conventional fertilizing（ 50 FS）. The dynamic characteristics and emission factors of CO2,CH4 and N2O in the soil were analyzed using an in-situ,closed chamber,gas chromatography-based system,from November 2016 to September 2017. The results showed that the emission of CO2,CH4 and N2O has seasonal variation characteristics. The peak value mainly occurred in April to August,and the gas emission peak would appear after fertilizing and irrigating. Compared with F treatment,straw returning with fertilizing treatments reduced the N2O emission fluxes,cumulative emission and emission factor,especially in the 100 FS treatment. The N2O cumulative emission and emission factor was 60. 76 kg·hm^-2,0. 138 kg·kg^-1（ N2O-N/N） respectively in 100 FS treatment during planting chili was more than that during planting lettuce and cabbage.Moreover,straw returning with reducing conventional fertilizing could reduce the N2O emission factor compared with 100 FS treatment.The CO2 emission fluxes 55. 28-1 831. 62 [mg·（ m2·h）^-1] and cumulative emission（ 7 502. 13-25 988. 55 kg·hm^-2） in 70 FS treatment were lower than that in CK and F treatments,while other treatments increased the CO2 emission fluxes and cumulative emission,especially in 60 FS and 50 FS treatments. During planting lettuce and cabbage,the CH4 cumulative emission mainly showed negative values in treatments except for CK,indicating that soil could adsorb CH4. Moreover,straw returning with 30%-50%conventional fertilizing treatment could reduce CH4 emission fluxes and cumulative emission during planting chili,but increased in100 FS. Compared with CK and F treatment,generally,straw retuning with conventional fertilizing could significantly increase the global warming potential（ GWP） in the study,except for 70 FS treatment. 70 FS could reduce the CO2,CH4 emission and the GWP ofgreenhouse gases,but could not significantly affect N2O emission reduction.