冬季水分管理和水稻覆膜栽培对川中丘陵地区冬水田CH4排放的影响

采用静态箱-气相色谱法观测冬季水分管理和水稻覆膜栽培对川中丘陵地区冬水田全年的CH_4排放通量。试验设置持续淹水(CF)、冬季直接落干+稻季淹水(TF)与冬季覆膜落干+稻季覆膜(PM)3个处理。结果表明,冬季休闲期,CF、TF和PM处理CH_4排放分别为16.1、1.4 g/m~2和2.7 g/m~2;水稻生长期,CF、TF和PM处理CH_4排放分别为57.7、27.7 g/m~2和13.5 g/m~2。相较于CF处理,TF与PM处理分别减少其全年CH_4排放60.6%和78.0%。TF与PM处理水稻生长期CH_4排放峰值分别较CF处理低33.0%和56.1%。休闲期,TF、PM处理厢面与厢沟区域CH_4排放与土壤温度显著正相关(P0.05),与土壤氧化还原电位(土壤Eh)显著负相关(P0.05),而CF处理CH_4排放仅与土壤温度显著正相关(P0.05)。水稻生长期,CF处理CH_4排放与土壤温度显著正相关(P0.05),与土壤Eh显著负相关(P0.05),TF处理CH_4排放仅与土壤Eh显著负相关(P0.05),PM处理厢沟CH_4排放与土壤Eh显著正相关(P0.05)。各处理水稻生长期土壤可溶性有机碳含量(DOC)与微生物生物量碳含量(MBC)显著高于休闲期(P0.05)。研究结果为进一步研究冬水田全年CH_4排放规律及寻求有效的减排措施提供数据支撑和科学依据。

Effects of water management in winter and of plastic film mulching during rice cultivation on CH4 emission from paddy field in a hilly region of Central Sichuan

Methane (CH₄) is one of the most important greenhouse gases and plays an important role in atmospheric chemistry. Rice fields have been identified as an important source of atmospheric CH₄. Because permanently flooded paddy fields create the most favorable situation for CH₄ production and emit CH₄ all year round, they are thought to contribute the greatest amounts of CH₄. Draining the permanently flooded paddy fields in the fallow season is supposed to be a good option for mitigating CH₄ emission. However, those paddy fields distributed in the hilly area of southwest China face the problem of water shortage. This means that transplanting rice in the following year would be hindered, if the fields were drained in the previous fallow season. In recent years, a new technology involving improved plastic film mulching for rice cultivation has been developed. It is an alternative to permanently flooded rice cultivation technology, which promises to save water, and in addition, would allow drainage in the fallow season without impeding the next rice transplanting session. The effects of water management in winter and of plastic film mulching during rice cultivation on CH₄ emission throughout the year were explored using winter paddy fields in the hilly region of Central Sichuan. A field experiment was carried out using the static chamber-gas chromatograph method to monitor CH₄ emissions in the paddy fields. Three treatments were designed: Treatment CF (continuous flooding all year round), Treatment TF (drained in winter and flooded during the rice growing season), and Treatment PM (drained and mulched in winter and mulched during the rice growing season). The results showed that methane emission for Treatments CF, TF, and PM was 16.1 g/m², 1.4 g/m², and 2.7 g/m², respectively, during the winter fallow season and 57.7 g/m², 27.7 g/m², and 13.5 g/m², respectively, during the rice-growing season. Compared with Treatment CF, Treatments TF and PM reduced the annual CH₄ emission by 60.6% and 78.0%, respectively, and lowered the CH₄ flux peak during the rice-growing season by 33.0% and 56.1%, respectively. During the fallow season, in Treatments TF and PM, CH₄ emission from ridge and ditch areas was significantly correlated with soil temperature (P < 0.05), but negatively with soil redox potential (soil Eh) (P < 0.05). However, CH₄ emission was positively correlated with soil temperature in Treatment CF (P < 0.05). During the rice-growing season, in Treatment CF, CH₄ emission was significantly and positively related to soil temperature (P < 0.05), and negatively to soil Eh (P < 0.05). In Treatment TF, CH₄ emission was only negatively related to soil Eh (P < 0.05), and in Treatment PM, CH₄ emission from the ditches was significantly and positively related to soil Eh (P < 0.05). The soil dissolved organic carbon (DOC) and soil microbial biomass carbon (MBC) contents were much higher during the rice-growing season than during the fallow season (P < 0.05). The findings may provide important data and a scientific basis for further study of the process of CH₄ emission from permanently flooded paddy fields throughout a year and to explore effective mitigation options for CH₄ emission in more detail.