Nitrogen balance in paddy fields under flowing-irrigation condition
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ORIGINAL ARTICLE
Nitrogen balance in paddy fields under flowing-irrigation condition Makoto Saiki . Thi Phuong Mai Nguyen . Junko Shindo . Kei Nishida
Received: 13 February 2019 / Accepted: 31 August 2019 Ó Springer Nature B.V. 2019
Abstract Flowing irrigation which drains a large volume of water is one of agricultural techniques for ensuring rice quality. In this study, the nitrogen input and output were characterised in paddy fields under flowing irrigation based on observation in Central Japan, and the estimated nitrogen loadings were compared to the reported values in traditional paddy fields under stagnant irrigation by using budget analysis. The annual water fluxes in the studied fields were calculated to be more than ten times larger than those in traditional fields. The concentrations of most nitrogen forms in surface drainage and subsurface drainage were detected at highest level during paddling periods, while those of nitrate and nitrite in subsurface drainage increased during non-irrigation periods. The total nitrogen inputs were at upper level (236–332 kg N ha-1) of or larger (490–581 kg N ha-1) than
M. Saiki Graduate School of Medicine, Engineering and Agriculture, University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-0016, Japan T. P. M. Nguyen Institute of Environmental Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi, Vietnam J. Shindo K. Nishida (&) Interdisciplinary Centre for River Basin Environment (ICRE), University of Yamanashi, 4-4-37 Takeda, Kofu, Yamanashi 400-0016, Japan e-mail: [email protected]
the reported values under both flowing irrigation and stagnant irrigation, and the larger contribution of irrigation pathway was observed. Surface drainage (78.3–163.5 kg N ha-1) and transport to underground system (73.1–210.4 kg N ha-1) were significantly higher than reported values obtained from stagnantirrigation paddy fields. The differences between input and output were thereby estimated and the large negative balance was attributed to the soil accumulation, which was distinctly detected in the field with presumably higher adsorption capacity. Therefore, assessing the effect of water flow on soil nitrogen accumulation as well as discharge is recommended by evaluating nitrogen balance in paddy field. Keywords Rice cultivation Water pollution Budget analysis Soil accumulation
Introduction Paddy fields cause nitrogen pollution in surface and subsurface water environments (Cho et al. 2000; Guo et al. 2004; Shinozaka et al. 2016). Nitrogen flow is detected in the paddy fields as several types of inputs or outputs. Inputs include fertiliser, irrigation, precipitation and biological nitrogen fixation, whereas outputs include the assimilation of rice, surface drainage and underground flow, denitrification, volatilisation, assimilation by other plants including
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Nutr Cycl Agroecosyst
algae, and accumulation in soil (Takakai et al. 2017; Liang et al. 2007; Antonopoulos 2010). B
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