水旱轮作稻田旱作季种植不同作物对CH_4和N_2O排放的影响

Effects of different upland crops cultivation on CH_4 and N_2O emissions during upland-growing season from paddy rice-upland crop rotation field

甲烷(CH4)和氧化亚氮(N2O)是仅次于二氧化碳(CO2)的重要温室气体,农田是大气CH4和N2O的重要来源,但目前农业措施对CH4和N2O排放的影响尚不明确。以水旱轮作稻田旱作季休闲为对照,采用静态箱-气相色谱法研究了种植紫云英、黑麦草、冬小麦以及油菜等4种作物对稻田旱作季CH4和N2O排放及其温室效应的影响。结果表明:水旱轮作稻田旱作季CH4排放通量较低,而N2O排放较为明显。稻田旱作季CH4平均排放通量表现为油菜>黑麦草>冬小麦>紫云英>休闲,依次为8.96、7.19、6.94、6.52和6.02μg·m-2·h-1,季节N2O平均排放通量的顺序是油菜(61.1μg·m-2·h-1)>冬小麦(52.5μg·m-2·h-1)>黑麦草(34.0μg·m-2·h-1)>休闲(15.3μg·m-2·h-1)>紫云英(13.6μg·m-2·h-1)。稻田旱作季种植不同作物对CH4和N2O季节总排放量的影响达到极显著水平(P<0.01),CH4和N2O季节总排放量均以种植油菜为最大,分别达到43.2和294.7 mg·m-2,比对照休闲增加49%和299%。种植油菜、冬小麦和黑麦草较对照休闲显著增加稻田旱作季总增温潜势(P<0.05),紫云英和休闲处理间总增温潜势无显著差异(P>0.05)。研究表明,种植油菜、冬小麦和黑麦草等作物由于氮肥的施用增加了水旱轮作稻田旱作季温室效应。

Although carbon dioxide （CO2） is by far the most abundant greenhouse gas, methane （CH4） and nitrous oxide （N20） are also important because of their unique radiative properties and long residence time in the atmosphere resulting in global warming potentials （GWPs） of 298 and 25 times that of CO2, respectively. Though much research has focused on CH4 and N20 emissions under various agricultural managements （such as soil tillage, crop straw management, water regime, fertilizers, et al）, the impact of crop cultivation on CH4 and N20 emission is currently not well documented. By using static chamber/gas chromatographic techniques, this paper studied the different upland crops cultivation on CH4 and N20 emissions during upland-growing season from paddy rice-upland crop rotation field, including Chinese milk vetch （T1）, ryegrass （T2）, winter wheat （T3） and rape （T4）, with fallow as control （CK）. The results showed that paddy field was a weak source of atmospheric CH4 and an obvious source of atmospheric N20 as well during upland-growing season. The order of seasonal CH4 fluxes was T4 〉 T2 〉 T3 〉 T1 〉 CK （mean 8.96, 7.19, 6.94, 6.52 and 6.02 μg·m-2·h-1, respectively）, while seasonal mean N20 fluxes were： T4 （61.1 μg·m-2·h-1） 〉 T3 （52.5 μg·m-2·h-1） 〉 T2 （34.0 μg·m-2·h-l） 〉 CK （15.3 μg·m2·h-1） 〉 T1 （13.6 μg·m-2·h-l）. Total CH4 and N20 emissions were significantly influenced by upland crops cultivation during upland-growing season （P〈0.01）. T4 had the highest total CH4 and N20 emissions during upland-growing season, with 43.2 and 294.7 mg·m-2, respectively. Compared with CK, T4 increased total CH4 and N20 emissions by 49% and 299%, respectively. T4, T3 and T2 significantly increased GWPs of CH4 and N20 during upland-growing season in contrast with CK （P〈0.05）. The results of this preliminary study suggest that GWPs of CH4 and N20 were significantly promoted by planting rape, winter wheat and ryegrass due to nitrogen fertilizer application during upland-growing season from paddy rice-upland crop rotation field.