期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 115, 期 39, 页码 9720-9725出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1809276115
关键词
rice; nitrous oxide; methane; alternate wetting and drying; water
资金
- ICCO Foundation
- Brot fuer die Welt
Global rice cultivation is estimated to account for 2.5% of current anthropogenic warming because of emissions of methane (CH4), a short-lived greenhouse gas. This estimate assumes a widespread prevalence of continuous flooding of most rice fields and hence does not include emissions of nitrous oxide (N2O), a long-lived greenhouse gas. Based on the belief that minimizing CH4 from rice cultivation is always climate beneficial, current mitigation policies promote increased use of intermittent flooding. However, results from five intermittently flooded rice farms across three agroecological regions in India indicate that N2O emissions per hectare can be three times higher (33 kg-N2O center dot ha(-1).season-1) than the maximum previously reported. Correlations between N2O emissions and management parameters suggest that N2O emissions from rice across the Indian subcontinent might be 30-45 times higher under intensified use of intermittent flooding than under continuous flooding. Our data further indicate that comanagement of water with inorganic nitrogen and/or organic matter inputs can decrease climate impacts caused by greenhouse gas emissionsupto90% andnitrogenmanagementmight not be central toN(2)Oreduction. An understanding of climate benefits/ drawbacks over time of different flooding regimes because of differences in N2O and CH4 emissions can help select the most climatefriendly water management regimes for a given area. Region-specific studies of rice farming practices that map flooding regimes and measure effectsofmultiple comanagedvariablesonN(2)OandCH(4) emissions are necessary to determine and minimize the climate impacts of rice cultivation over both the short term and long term.
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