Nitrogen Transport/Deposition from Paddy Ecosystem and Potential Pollution Risk Period in Southwest China

• Published in: Water (Basel) Vol. 14; no. 4; p. 539
• Main Authors: Guo, Shufang, Yan, Tiezhu, Zhai, Limei, Yen, Haw, Liu, Jian, Li, Wenchao, Liu, Hongbin
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2022
• Subjects: Agriculture; atmospheric deposition; cropland; drainage; Ecosystems; Eutrophication; fertilizer application; Fertilizers; Fresh water; Irrigation; Lakes; Nitrates; Nitrogen; paddies; Pollution; Precipitation; Rain; Rice; risk; runoff; Seasons; soil; total nitrogen; volatilization; water flow; water quality; Watersheds; China; Europe
• ISSN: 2073-4441; 2073-4441
• DOI: 10.3390/w14040539

Nitrogen (N) losses through runoff from cropland and atmospheric deposition contributed by agricultural NH3 volatilization are important contributors to lake eutrophication and receive wide attention. Studies on the N runoff and atmospheric N deposition from the paddy ecosystem and how the agriculture-derived N deposition was related to NH3 volatilization were conducted in the paddy ecosystem in the Erhai Lake Watershed in southwest China. The critical period (CP) with a relatively high total N (TN) and NH4+-N deposition occurred in the fertilization period and continued one week after the completion of fertilizer application, and the CP period for N loss through surface runoff was one week longer than that for deposition. Especially, the mean depositions of NH4+-N in the CP period were substantially higher than those in the subsequent period (p < 0.01). Moreover, agriculture-derived NH4+ contributed more than 54% of the total NH4+-N deposition in the CP period, being positively related to NH3 volatilization from cropland soil (p < 0.05). The N concentrations were higher in the outlet water of ditches and runoff in May than in other months due to fertilization and irrigation. Therefore, to reduce the agricultural N losses and improve lake water quality, it is important to both reduce agricultural NH4+-N deposition from NH3 volatilization and intercept water flow from the paddy fields into drainage ditches during the CP.