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| DOI：10.13522/j.cnki.ggps.2025007 |
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| Effects of different irrigation methods on dynamics and transformation of nitrogen in paddy fields |
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WANG Siyu, SUN Xuemei, CHEN Mo
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1. School of Hydraulic and Electric-Power, Heilongjiang University, Harbin 150080, China;
2. Heilongjiang Province Hydraulic Research Institute, Harbin 150080, China
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| Abstract: |
| 【Objective】Efficient irrigation management is critical for optimizing soil nitrogen dynamics and its uptake by rice in paddy fields. This paper investigates the effects of irrigation methods on the dynamics of ammonium nitrogen (NH4?-N), nitrate nitrogen (NO3--N) and alkali-hydrolysable nitrogen (AN) across the soil profiles, in attempts to provide an optimal irrigation strategy to sustain rice production in paddy fields.【Method】The field experiment compared three irrigation methods: shallow irrigation (QS) keeping a thin water layer on the soil surface; shallow irrigation with the root-zone soil water content being controlled at 80% of saturated water content (QSG), and deep irrigation keeping a deep water layer on the soil surface with the root-zone soil water content controlled at 80% of saturated water content (SSG). During the experiment, we measured the contents and transformation of NH4+-N, NO3--N and AN at different growing stages along the soil profile. Further measurements were made 1, 3, 5 and 7 days after nitrogen fertilization.【Result】Nitrogen content decreased as crop grew and soil deepened in all three irrigation methods. Compared with other treatments, QSG significantly increased NH4+-N, NO3--N, and AN in the 0-20 cm soil layer. Compared with QS and SSG, QSG increased the contents of NH4+-N, NO3--N and AN in the 0-10 cm soil layer by 13.91%-133.26%, 26.11%-273.75% and 2.8%-13.9%, respectively. Applying yellow humic acid significantly increased NH4+-N in the topsoil initially. However, the subsequent leaching of NH4+-N increased NO3--N content in the subsoil. The change in AN in nitrogen transformation provides a nitrogen source to the crop.【Conclusion】Shallow irrigation combined with the root-zone soil water content controlled at 80% of the saturated water content is the optimal irrigation strategy for paddy fields. Controlling the upper and lower irrigation limits can increase nitrogen retention. This will help optimize fertilizer management, sustainably improve rice yield in paddy fields. |
| Key words: nitrate nitrogen; ammonium nitrogen; alkaline hydrolyzable nitrogen; rice irrigation patterns |
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