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| Effects of different rainfall intensities and vegetation coverages on runoff and nitrogen loss from rice fields |
| Received:April 13, 2021 |
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| KeyWord:non-point source pollution;paddy field;surface runoff;nitrogen loss;temporal characteristic |
| Author Name | Affiliation | E-mail | | YAN Lei | Key Lab of Agro-environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China | | | DENG Xuzhe | School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212001, China | | | XUE Lihong | Key Lab of Agro-environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212001, China | | | HOU Pengfu | Key Lab of Agro-environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212001, China | pengfuhou100smby@163.com | | XU Defu | School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China | | | YANG Linzhang | Key Lab of Agro-environment in Downstream of Yangtze Plain, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China | |
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| Abstract: |
| To develop strategies to reduce the risk of non-point source pollution, it is important to elucidate the characteristics of runoff and nutrient loss. This understanding will inform the development of farmland runoff reduction strategies, which will reduce the risk of nonpoint source pollution. To understand the response of runoff and nitrogen loss from paddy fields to rainfall intensity, three rainfall intensities[small(SI), 30 mm·h-1; middle(MI), 60 mm·h-1; and large(LI), 90 mm·h-1] were selected for the field rainfall simulation experiment. The experiment was conducted in the early(low vegetation coverage, LVC) and late(high vegetation coverage, HVC) rice growing stages. The results showed that the runoff rate in paddy fields first rose and then fell with runoff duration; the peak runoff rate increased with rainfall intensity. The peak runoff rates at different rainfall intensities were 72.58(SI), 126.45(MI) and 234.90(LI) m3·hm-2·h-1 under LVC, and 41.94(SI), 70.02(MI), 83.30(LI) m3·hm-2·h-1 under HVC. In addition, the nitrogen concentration in runoff water was the highest during the initial runoff period. The relationship between the nitrogen concentration and the duration of this concentration for different rainfall intensities under the two vegetation coverages was described using a logarithmic functional equation:[Y=a-b×ln(X + c), P<0.01]. As opposed to the nitrogen concentration, the risk of nitrogen loss was higher during the first 40 min following the onset of runoff. This was influenced by the runoff rate, particularly during the initial 20~30 min after the runoff(time of peak loss rate). The nitrogen loss rate under LVC was more likely to be affected by rainfall intensity. The peak runoff rates at different rainfall intensities were 0.07 (SI), 0.10 (MI), 0.27 (LI) kg·hm-2·h-1 under LVC, and 0.05(SI), 0.04(MI), 0.06(LI) kg·hm-2·h-1 under HVC. As such, the loads of nitrogen loss with different rainfall intensities varied significantly under LVC, and nitrogen loss at high rainfall intensity(10.02 mg·m-2) was considerably greater than that at moderate and low rainfall intensities. Here, ammonium nitrogen(NH4+-N) was the major form of nitrogen loss(accounting for approximately 41%~52%). The nitrogen loss load was closely related to the runoff rate and nitrogen concentration in the initial(0~20 min) and middle(20~40 min) runoff periods. The results suggest that during the initial runoff period, the nutrient concentration peaks, whereas the nitrogen loss rate in paddy fields is the highest within 20~30 min after the onset of runoff. The runoff in the LVC scenario is more likely to be affected by rainfall intensity. |
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