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| Effect of temperature on gross N transformation rates in cropland black soil |
| Received:September 27, 2020 |
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| KeyWord:temperature;black soil;15N trace;gross N transformation rates |
| Author Name | Affiliation | E-mail | | LANG Man | Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China
School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China | | | LI Ping | Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China
School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China | pli@nuist.edu.cn | | WEI Wei | Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China
School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China | |
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| Abstract: |
| The processes of N supply, retention, consumption, and loss in cropland soil at different temperatures were explored to provide a scientific basis for the rational application of N fertilizer. A paired 15N tracing incubation trial(15NH4NO3, NH415NO3, 15N isotopic excess of 5 atom%, and N concentration of 60 mg N·kg-1) combined with a numerical FLUAZ model was conducted to investigate the responses of the gross N mineralization rate, gross N immobilization rate, and gross nitrification rate in a cropland black soil in Heilongjiang Province, China to temperature changes(15, 25, and 35℃) at 60% water holding capacity. The results showed that the gross N mineralization rates increased significantly as the temperature increased in the range of 15~35℃, but the increase in amplitude in the range of 25~35℃ was smaller than that in the range of 15~25℃. In the range of 15~25℃, the gross N immobilization and nitrification rates increased significantly as the temperature increased, whereas these two rates decreased significantly as the temperature increased in the range of 25~35℃, but were still higher than those of the 15℃ treatment. The ratios of the gross N mineralization rate to immobilization rate(gm/gi) and gross nitrification rate to ammonium immobilization rate(gn/ia) were slightly higher than 1 at 15℃ and 25℃, respectively, and there was no significant difference between the two treatments, whereas these two ratios were both significantly higher than 1 at 35℃. The results indicated that the processes of N mineralization and immobilization were coupled relatively tightly at temperatures ranging from 15℃ to 25℃, and the risks of nitrate accumulation and leaching were lower. The mineralization rate of organic N and the nitrification rate significantly exceeded the ammonium immobilization rate after the temperature increased to 35℃, and nitrification was the dominant pathway of ammonium consumption in the soil, thereby increasing the potential risks of nitrate accumulation, denitrification, and leaching. |
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