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 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 stagnant-irrigation 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.
Highlights
Paddy fields cause nitrogen pollution in surface and subsurface water environments (Cho et al 2000; Guo et al 2004; Shinozaka et al 2016)
In Japan, Sugimoto et al (2008) observed that 78 kg N ha-1 of applied fertiliser resulted in surface drainage loading of 41.6 kg N ha-1 that was higher than the value reported by Liang et al (2007) with similar or higher level of fertilisation
The nitrogen balances for two paddy fields were estimated under flowing-irrigation condition using four factors as inputs and seven factors as outputs
Summary
Paddy fields cause nitrogen pollution in surface and subsurface water environments (Cho et al 2000; Guo et al 2004; Shinozaka et al 2016). In Japan, Sugimoto et al (2008) observed that 78 kg N ha-1 of applied fertiliser resulted in surface drainage loading of 41.6 kg N ha-1 that was higher than the value reported by Liang et al (2007) with similar or higher level of fertilisation. According to these researches, some cases showed that the output loading increased with an increase in input from fertiliser in the same field but others showed that the output was not directly related with the amount of fertiliser when the experimental results in different fields were compared. To ensure sustainable water environment, it is important to estimate and evaluate the nitrogen loading considering all the processes that occur in paddy fields
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
