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| DOI：10.13522/j.cnki.ggps.2021081 |
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| CH4 and N2O Emissions from Rice Field as Affected by Different Combinations of Irrigation and Nitrogen Fertilization |
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LI Yifan, LI Luobu, LI Fusheng
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College of Agriculture, Guangxi University, Nanning 530005, China
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| Abstract: |
| 【Objective】Greenhouse gas emissions from agricultural soils are modulated by a multitude of abiotic and biotic factors, and the objective of this study is to elucidate how irrigation and nitrogen (N) fertilization combine to affect emissions of methane (CH4) and nitrous oxide (N2O) from double-harvest rice field in south China.【Method】The experiment was conducted in a rice field and compared three irrigations: conventional irrigation (CK), thin-wet-dry irrigation (TR), alternate wet and dry irrigation (DR); and three N fertilizations:120 kg/hm2 with 20% used for basal and 80% for topdressing (FN1), 120 N kg/hm2 with 50% for basal and 50% for topdressing (FN2), 90 N kg/hm2 with 50% for basal and 50% for topdressing (FN3). In each treatment, we measured crop yield, emission of CH4 and N2O, and then calculated their global warming potential (GWP) and GHG emission intensity (GHGI).【Result】Compared with CK combined with FN1 or FN2, DR combined with FN1 or FN2 increased total yield of the rice at the two seasons by 17.9% and 21.1%, respectively. In contrast, combing TR or CK with FN1 increased the yield of the early rice and the yields of the rice in the two seasons by 13.4% and 11.4%, and 16.1% and 12.6%, respectively, compared with their combination with FN2. Under DR irrigation, FN3 increased the early rice yield by 11.0% compared to FN2. Of all treatments, DR+FN1 was optimal in increasing total yield of the rice in the two seasons. Compared to CK, TR and DR reduced the cumulative CH4 emissions over the whole growth season by 17.1%~22.5% and 43.0%~56.8%, respectively; but when combined with FN1 or FN2, they increased the cumulative N2O emissions by 69.3%~85.2% and 146.2%~160.7%, respectively. Combing TR and FN2 reduced the cumulative CH4 and N2O emissions by 26.8% and 32.3%, respectively, compared to its combination with FN3.【Conclusion】In terms of irrigation, TR and DR reduced both GWP and GHGI compared to CK, especially DR. In terms of N fertilization, FN1 and FN3 emitted less gases than FN2, especially FN1. Therefore, TR and DR combined with reduced N application was more effective to mitigate GWP and GHGI, especially after reducing its proportion for basal application. |
| Key words: “Thin-wet-dry” irrigation; alternate wetting and drying irrigation; CH4 and N2O emission; global warming potential; greenhouse gas emission intensity |
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