Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigati...Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigation is one promising practice that has been shown to reduce CH4 emissions. However, little is known about the impact of this practice on N20 emissions, in particular under Mediterranean climate. To close this knowledge gap, we assessed how AWD influenced grain yield, fluxes and annual budgets of CH4 and N20 emissions, and global warming potential （GWP） in Italian rice systems over a 2-year period. Overall, a larger GWP was observed under AWD, as a result of high N20 emissions which offset reductions in CH4 emissions. In the first year, with 70% water reduction, the yields were reduced by 33%, CH4 emissions decreased by 97%, while N20 emissions increased by more than 5-fold under AWD as compared to PF; in the second year, with a 40% water saving, the reductions of rice yields and CH4 emissions （13% and 11%, respectively） were not significant, but N20 fluxes more than doubled. The transition from anaerobic to aerobic soil conditions resulted in the highest N20 fluxes under AWD. The duration of flooding, transition to aerobic conditions, water level above the soil surface, and the relative timing between fertilization and flooding were the main drivers affecting greenhouse gas mitigation potential under AWD and should be carefully planned through site-specific management options.展开更多
A four-year(2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier(CRF, thermoplastic resin-coated urea in this study) ...A four-year(2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier(CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4ha-1in treatments CK(zero N), U(urea) and C(CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7%(P < 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration(MSA) starting on D30(30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.展开更多
基金funded by Mars Belgium NV (Mars Food) and Ministero delle Politiche Agrarie, Alimentari e Forestali of Italy (POLORISO project, D.M.5337, Dec.5, 2011)
文摘Reducing CH4 and N20 emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying （AWD） irrigation is one promising practice that has been shown to reduce CH4 emissions. However, little is known about the impact of this practice on N20 emissions, in particular under Mediterranean climate. To close this knowledge gap, we assessed how AWD influenced grain yield, fluxes and annual budgets of CH4 and N20 emissions, and global warming potential （GWP） in Italian rice systems over a 2-year period. Overall, a larger GWP was observed under AWD, as a result of high N20 emissions which offset reductions in CH4 emissions. In the first year, with 70% water reduction, the yields were reduced by 33%, CH4 emissions decreased by 97%, while N20 emissions increased by more than 5-fold under AWD as compared to PF; in the second year, with a 40% water saving, the reductions of rice yields and CH4 emissions （13% and 11%, respectively） were not significant, but N20 fluxes more than doubled. The transition from anaerobic to aerobic soil conditions resulted in the highest N20 fluxes under AWD. The duration of flooding, transition to aerobic conditions, water level above the soil surface, and the relative timing between fertilization and flooding were the main drivers affecting greenhouse gas mitigation potential under AWD and should be carefully planned through site-specific management options.
基金Supported by the Key Program for International S&T Cooperation Projects of China(No.2012DFG90290)the Non-Profit Research Foundation for Agriculture,China(No.201103039)+1 种基金the National Natural Science Foundation of China(Nos.41271259 and 412012433)the Research Fund of State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences(No.Y412201414)
文摘A four-year(2008–2011) field study was implemented in a major rice-growing region of China to better understand the effect of urea and controlled release fertilier(CRF, thermoplastic resin-coated urea in this study) on CH4 emission from paddy fields. Over the four years, the average CH4 emission during the rice growing seasons was 76.9, 65.8 and 64.9 kg CH4ha-1in treatments CK(zero N), U(urea) and C(CRF), respectively. Urea and CRF significantly reduced CH4 emission by 14.4% and 15.6%, and increased average rice grain yield by 25.8% and 19.7%(P < 0.05), respectively, compared with treatment CK. Flooding duration would affect CRF's effect on CH4 emission from paddy fields. Under normal aeration conditions, CH4 emission tended to be 3.9%–15.2% lower in treatment C than in treatment U from 2009 to 2011, while it tended to be 4.2% higher under delayed aeration conditions in 2008. The findings suggest that mid-season aeration(MSA) starting on D30(30 days after rice transplanting), just like the local practice, would optimize the CRF's effect on CH4 emission from rice fields in China. Over the four years, average rice yield did not differ between treatments U and C, and tended to be 5% lower in treatment C than in treatment U.
