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| N balance analysis and adjusting countermeasures of small watershed in subtropical hilly area |
| Received:October 24, 2016 |
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| KeyWord:subtropics;small watershed;nitrogen budget;agricultural non-point source pollution |
| Author Name | Affiliation | E-mail | | HAN Zeng | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | WANG Mei-hui | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | ZHOU Jiao-gen | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | zhoujg@isa.ac.cn | | WANG Yi | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | SHEN Jian-lin | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Xi | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | | | LI Yu-yuan | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | liyy@isa.ac.cn | | WU Jin-shui | Key Laboratory of Subtropical Agro-ecological Processes, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, China | |
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| Abstract: |
| Two small watersheds(about 50 km2) were selected as the study region in subtropical hilly area in Changsha County, Hunan Province. By establishing N budget framework model and using data of in situ observation, door to door survey, and governmental statistical yearbooks, the input and output characteristics of nitrogen(N) and the main influencing factors were quantitatively analyzed during the 3-year period from 2012 to 2014. The results showed that N input, output, and surplus intensities in the small watersheds were averagely 312.0, 165.1, and 146.9 kg·hm-2·a-1 for the agro-watershed(AW), while 160.2, 83.3, and 76.9 kg·hm-2·a-1 for the forest-agro-watershed (FAW), respectively. A similar input and output structure were found in the two small watersheds, the dominant N input were feed and fertilizer, which accounted for 73.4% in AW and for 63.9% in FAW, respectively. The gaseous loss, which included ammonia volatilization and denitrification, was an important pattern of N output, contributed more than 50%. However, the N output of products accounted for just 1/4-1/3 of the total. Therefore, reduction of fertilizer application and moderate livestock and poultry breeding scale are the major approaches of controlling N input in a subtropical watershed. Correspondingly, reducing the gaseous loss of N through technical measures and strengthening the N recycling use in a watershed are the primary measures in increasing N use efficiency and controlling agricultural non-point source pollution. |
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