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| DOI：10.13522/j.cnki.ggps.2020190 |
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| Nitrogen Loss with Rainfall Leaching from Paddy Field |
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LI Jiuying, WEI Qi, WANG Haiyu, CHEN Peng, CHENG Heng, XU Junzeng
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1. Heilongjiang Irrigation Drainage and Water Saving Technology Center, Harbin 150040, China; 2. College of Agricultural Science and Engineering, Hohai University, Nanjing 210098, China
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| Abstract: |
| 【Background】 Leaching of rainfall from farmland is a main nitrogen loss pathway from soil to surface and subsurface water bodies, and understanding its underlying mechanisms is crucial to improving water and fertilizer management.【Objective】 Focusing on paddy field, this paper investigated the variation in nitrogen loss with rainfall leaching aimed to provide guidance for improving water-fertilizer management and reduce nonpoint pollution in agricultural production.【Method】The experiment was conducted in a paddy field in 2019. In the experiment, we measured the variations in water drainage as well as the concentrations of nitrogen (TN, NH4+-N and NO3--N) during three rainfalls - 56.2, 104.4 and 147.6 mm that fell in 9, 10 and 18 days, respectively, in Heilongjiang province.【Result】①The water drained from the paddy field following a rainfall increased with the rainfall depth. Compared with water drainage 27.2 mm from the first rainfall, water drainage from the second and third rainfalls increased by 85.8% and 154.3% respectively, indicating that the increase in water drainage was greater than the increase in the rainfall. The third rainfall was 23.0% more than the first one, but its associated water drainage from the soil was 85.3% more than that from the first one. ②The nitrogen concentrations in the drainage water showed a similar pattern, increasing firstly followed by an asymptotic decline regardless of the rainfall events. The concentration of TN, NH4+-N and NO3--N associated with the three rainfalls varied in the range of 3.3~14.4, 2.3~5.3 mg/L and 1.4~4.3 mg/L, respectively, lower than the requirements set by the IV Standard of Corresponding Index of Surface Water Quality. ③The load of TN, NH4+-N and NO3--N in the drainage water associated with the second and third rainfalls increased by 1.7~4.6, 0.7~1.9 kg/hm2 and 0.1~0.9 kg/hm2, respectively, compared with those in the first one.【Conclusion】Nitrogen leaching from the paddy field from July to September is a main source of the nonpoint pollution in agricultural production in Heilongjiang province. Reducing fertilization prior to the monsoon seasons and improving drainage management following rainfalls could help reduce nitrogen leaching and ameliorate agricultural nonpoint source pollution. |
| Key words: rainfall; paddy field drainage; nitrogen loss; nonpoint source pollution in agriculture |
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