土壤氧气可获得性对双季稻田温室气体排放通量的影响

为探讨土壤氧气可获得性(SOA)对双季稻田温室气体排放的影响,利用静态箱气相色谱法对多种管理措施影响下稻田温室气体排放通量和土壤氧化还原电位(Eh)、pH值及田间淹水深度(H)等3种SOA因子进行了观测。结果表明,甲烷(CH₄)排放最集中的Eh值、pH值和H范围分别为-100-0mV、5 < pH < 6和1-5cm,3个范围内分别观测到48.8%、61.1%和77.0%的CH₄排放,其中H对CH₄排放影响最明显,单独由其就可解释37.8%的CH₄排放通量(P < 0.0001)。对于氧化亚氮(N₂O),观测到较多的负通量,其纯排放最密集的3种SOA因子的范围分别是:0-100mV、5 < pH < 6和1-5cm,而200-300mV是其排放的临界Eh范围,高于此范围N₂O排放极少。厌氧的反硝化过程是双季稻田N₂O产生的主导过程。可为水稻田温室气体排放机理研究提供基础数据。

The effect of soil oxygen availability on greenhouse gases emission in a double rice field

To investigate the effect of soil oxygen availability (SOA) on greenhouse gas (GHG) emissions from a double-rice cropping field, a two-year observation of greenhouse gas emissions of seven treatments from a rice paddy field was conducted by using the static closed-chamber method. There were seven management practices (or treatments), including CWS (Conventional Tillage Without Straw Residues Urea), NWS (No Tillage Without Straw Residues Urea), SCU (Conventional Tillage Without Straw Residues Controlled-Release Urea), HN (High Stubbles No Tillage Urea), HC (High Stubbles Conventional Tillage Urea), SN (Straw Cover No Tillage Urea) and SNF (Straw Cover No Tillage Urea Continuous Flooding). Three SOA factors, i.e., soil redox potential (Eh), pH and field water level (H) of each treatment was determined simultaneously. Our results indicated that methane emissions was sensitive to all of the three SOA factors. The critical values at which the higher methane fluxes were observed, for Eh, pH and H was -100-0mV, 5-6 and 1-5cm, respectively, and therefore the proportions of methane emitted from these three ranges were 48.8%, 61.1% and 77.0%, respectively. The determination coefficient of linear or quadratic polynomial regression models of the methane fluxes and the individual three SOA factors ranged from 0.04 to 0.38 (P < 0.05). Among of them, H was attributed to the most important influence on methane emissions, explaining 37.8% of the variance of methane emissions from paddy field (P < 0.05). While for nitrous oxide (N₂O), large amount of negative fluxes occurred, If only positive N₂O emissions considered, most of them were observed under conditions of 0mV < Eh < 100mV, 5 < pH < 6 and 1cm<H < 5cm. We found that an Eh range of 200-300mV was the critical Eh interval for N₂O production, over which there was almost no N₂O emissions. Moreover, the denitrification under anaerobic environment was regarded as the primary process for N₂O production. This study can provide basic data for the mechanic research of GHGs emission from paddy field.