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| Effects of enhanced UV-B radiation on nitrogen transformation in paddy soil |
| Received:October 11, 2019 |
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| KeyWord:UV-B radiation;paddy soil;nitrogen invertase;inorganic nitrogen;nitrous oxide |
| Author Name | Affiliation | E-mail | | ZHANG Yan-xue | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | HE Yong-mei | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Xiang | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | SHENG Jian-jun | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | ZHAN Fang-dong | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Yuan | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | | | LI Ming-rui | College of Resources and Environment, Yunnan Agricultural University, Kunming 650201, China | limingruiyn@163.com |
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| Abstract: |
| This paper aims to explore the effect of enhanced UV-B radiation on nitrogen transformation in rice paddy soil. A local traditional rice variety, Baijiaolaojing, was planted in Yuanyang terraced fields. The effects of enhanced UV-B radiation(0 kJ·m-2, 2.5 kJ·m-2, 5.0 kJ·m-2, and 7.5 kJ·m-2)on the activities of enzymes related to soil nitrogen conversion, inorganic nitrogen contents, and N2O emission in rice paddy soils during rice growing period were investigated. The results showed that enhanced UV-B radiation(5.0 kJ·m-2)significantly decreased the activities of nitrite reductase and urease in the soils at tillering and booting stages of rice. The activities of nitrite reductase at booting stage and urease at tillering stage were significantly higher than those at other stages. Compared to control treatment, the three enhanced UV-B radiation treatments significantly increased the activities of nitrate reductase and protease at the mature stage. Nitrate reductase activity at enhanced UV-B radiation treatments of 2.5, 5.0 kJ·m-2, and 7.5 kJ·m-2 at booting stage was significantly higher than that in other stages, and the protease activity for all treatments at tillering stage was significantly higher than that in other stages. Enhanced UV-B radiation at 2.5 kJ·m-2 significantly decreased NH4+-N content during the whole rice growth period except the jointing stage, while 5.0 kJ·m-2 UV-B radiation significantly increased NO3--N content in paddy soil during the whole rice growth period. Enhanced UV-B radiation significantly reduced N2O emission at jointing and booting stages, while it significantly increased N2O emission at the mature stage. Correlation analysis indicated that N2O emission flux from rice paddy soil significantly correlated with the NH4+-N content, while the NH4+-N content was significantly positively correlated with the NO3--N content and urease activity(P<0.01). At the rice growth period, enhanced UVB radiation increased the activities of nitrate reductase and protease, inhibited the activities of nitrite reductase and urease, promoted the transformation of NH4+-N to NO3--N in rice paddy soils, and thus reduced N2O emission at jointing and booting stages. |
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