太湖地区不同水旱轮作方式下稻季甲烷和氧化亚氮排放研究

为准确编制我国稻田温室气体排放清单及制定合理减排措施提供基础数据,选择太湖地区典型水稻种植区江苏省苏州市,研究设计了休闲水稻(对照,CK)、紫云英水稻(T1)、黑麦草水稻(T2)、小麦水稻(T3)和油菜水稻(T4)5种水旱轮作方式,采用静态箱气相色谱法,开展了不同水旱轮作方式下水稻生长季田间甲烷(CH4)和氧化亚氮(N2O)排放监测试验。试验结果表明:不同水旱轮作方式下水稻生长季CH4排放通量呈先升高后降低的变化趋势,CH4排放峰值出现在水稻生育前期,移栽至有效分蘖临界叶龄期CH4累积排放量占全生育期排放总量的比例为65%~81%,而N2O仅在水稻烤田期间有明显排放。水旱轮作方式对稻季CH4和N2O排放有极显著(P 0.01)影响,CH4季节总排放量表现为T1(283.2 kg.hm 2)CK(139.5 kg.hm 2)T3(123.4kg.hm 2)T4(114.7 kg.hm 2)T2(100.8 kg.hm 2),N2O季节总排放量顺序为T1 T4 T3 T2 CK,依次为1.06kg.hm 2、0.87 kg.hm 2、0.81 kg.hm 2、0.72 kg.hm 2和0.53 kg.hm 2。T1处理稻季排放CH4和N2O产生的增温潜势最高[7 396 kg(CO2).hm 2],显著(P 0.05)高于其他处理,比CK[3 646 kg(CO2).hm 2]增加103%,T2[2 735kg(CO2).hm 2]较CK减少25%(P 0.05)。紫云英水稻轮作方式增加了太湖地区水稻生长季的温室效应。

Methane and nitrous oxide emission under different paddy-upland crop rotation systems during rice growth season in Taihu Lake Region

Methane (CH₄) and nitrous oxide (N₂O) are tow potent greenhouse gases (GHGs) that have contributed to global warming. The emissions of these gases from rice paddies have been affected by several factors, including climate, soil property, water regime, fertilizers, etc. Although research has focused on CH4 and N₂O emissions in rice paddies under various agro-management systems, little has been available on CH4 and N2O emissions from rice paddies under different paddy-upland crop rotation systems. To that end, a field experiment was conducted in the 2011 rice growth season to benefit scientific evaluation of GHG emissions and provide scientific strategies for developing rational measures to reduce GHGs emissions in paddy fields across China. Using static chamber/gas chromatographic techniques, the field experiment was conducted in Suzhou, Jiangsu Province simultaneously measured CH4 and N₂O emissions under five paddy-upland crop rotation systems. The five systems included fallow-rice (control, CK), Chinese milk vetch-rice (T1), ryegrass-rice (T2), winter wheat-rice (T3) and rape-rice (T4). The results showed characteristics seasonal variations in CH₄ emission under different paddy-upland crop rotation systems during rice growth season. Although CH₄ emission initially increased, it eventually declined in the course of the rice growth season. Peak CH₄ flux was during the early stage of rice growth. CH₄ cumulative emission from transplanting to the critical stage of productive tillering accounted for 65%~81% of the total emission during the rice growth season. Peak N₂O flux was only observed during midseason drainage period. Total CH₄ and N₂O emissions during the rice growth season were significantly influenced by paddy-upland crop rotation systems (P < 0.01). Total CH₄ emission under different paddy-upland crop rotation systems was in following order: T1 (283.2 kg·hm ²) > CK (139.5 kg·hm²) > T3 (123.4 kg·hm²) > T4 (114.7 kg·hm²) > T2 (100.8 kg·hm²). Total N₂O emission was in order of: T1 > T4 > T3 > T2 > CK, with respective means of 1.06 kg·hm², 0.87 kg·hm², 0.81 kg·hm², 0.72 kg·hm² and 0.53 kg·hm ². Combined global warming potential (GWP) of CH₄ and N₂O under T1 was 7 396 kg(CO₂)·hm², significantly higher than CK, T2, T3 or T4. Compared with CK [3 646 kg(CO₂)·hm²], T1 increased GWP by 103% while that of T2 [2 735 kg(CO₂)·hm²] decreased by 25%. The pilot study suggested that Chinese milk vetch-rice rotation intensified greenhouse effects during rice growth season in the Taihu Lake Region.