| Methane, as a contributor to climate change, is the next to carbon dioxide and on the basis of mass, the globalwarming potential (GWP) of CH4is about25times that of CO2on a100-year horizon Rice paddies are considered to be a major source of anthropogenic methane emission, and responsible for about5.3%～19%of the annual global efflux. Rice is one of the most important food crops in China, more than60%of the population live on rice. With the population growth and economic development, China’s grain demand will continue to show sustained rigid growth. By2030, China’s rice production must be increased by20%compared to the current level. On the premise of existing paddy field area is not reduced, further improve the yield of rice is the only way to ensure food security. In recent years, the promotion area of super rice with its remarkable yield advantage has increased rapidly in our country, in2011the promotion area had reach to1.1million mu, accounting for24.7%of rice planting area. At present, researches on CH4emission features and its relationships with growth characteristics mostly focus on the conventional rice varieties. While the research on super rice CH4emission is relatively scarce. The CH4emission from paddy rice are closely related to rice growth characteristics, whether the productivity advantage of super-rice will increase CH4emission, is an important problem which academics and politicians widely concerned. So far, understanding of super rice CH4emission features and its relationships with growth characteristics is still not very clear. Therefore, study on super rice methane emission and its relationship with plant characteristics, is not only beneficial to assess the methane emission of super rice, but also has important theoretical reference value to the plant type improvement and cultivation regulation of rice with high yield and low CH4emission in the future. Therefore, based on the manual closed static chamber-gas chromatography method, a pot experiment was conduced for thirty-three super-rice varieties in2011-2012in Nanjing Pailou Experiment Base of Nanjing Agricultural University. This study systematically and thoroughly analyzed the CH4emission features and its relationships with growth characteristics of super rice of different types in major rice producing regions of China. The results of this study are presented as follows:(1) Methane emission of super rice had two distinct peaks. One peak occurred at the active vegetative growth stage and the other at the panicle initiation stage of Northeast hybrid super rice, the middle and upper reaches of the Yangtze River and the lower reaches of the Yangtze River super rice. While, the two peak of Northeast conventional super rice respectively occurred at vegetative growth stage and milk stage.(2) Conventional super-rice methane emissions were higher than hybrid super-rice. The total methane emission of conventional super-rice and hybrid super-rice in Northeast were10.4and9.4g m-2, the former was10.6%higher than the latter. The total methane emission of conventional super-rice and hybrid super-rice in the middle and upper reaches of the Yangtze River were8.2and6.9g m-2, the former was18.8%higher than the latter (P<0.05). The total methane emission of conventional super-rice and hybrid super-rice the lower reaches of the Yangtze River were10.9and6.8g m-2, the former was37.6%higher than the latter.(P<0.01). The methane emissions of super rice in Northeast were mainly in the Seedling-Tillering period and Heading-Maturity period. While the methane emissions of super rice in the middle and upper reaches of the Yangtze River and the lower reaches of the Yangtze River were mainly in the Seedling-Tillering period.(3) Methane content in soil solution and methane emissions were closely related. Methane content in soil solution of conventional super rice in the lower reaches of the Yangtze River showed three peaks, appeared in active vegetative growth stage, panicle initiation stage and late stage of rice growth respectively. The first two peaks time of methane content in soil solution coincided with methane emission flux peak time. Methane content in soil solution of hybrid super rice in the lower reaches of the Yangtze River showed two peaks, appeared in panicle initiation stage and late stage of rice growth respectively. The first peak time of methane content in soil solution corresponded to the second peak time of methane emission flux. Methane content in soil solution of two different types super rice were positively correlated with the methane emission flux.(4) Plant characteristics of super-rice affected methane emission. A significantly positive correlation was found between the total methane emission and the maximum tiller number for all super-rice types. There was a significantly positive correlation between cumulative methane emissions at tillering stage and tillers (P<0.05). The effect of rice tillers on methane emission in the early stage of rice growth should be higher than that of in the late stage. While the correlations between methane emissions and plant the other growth characteristics depended on the variety type. Significantly positive correlation was found between methane emission and plant height for the conventional super-rice in the lower reaches of the Yangtze River (P<0.05). And the CH4emission was significantly negatively correlated with the maximum root dry weight and total aboveground biomass for the hybrid super-rice in the lower reaches of the Yangtze River (P<0.05). There was a significantly negative correlation between methane emission and grain yield for the hybrid super-rice in the middle and upper reaches of the Yangtze River (P<0.05) and in the lower reaches of the Yangtze River (P<0.01). |
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