Using DRAINMOD to Simulate the Impact of Irrigation and Drainage on Reaction and Movement of Water and Nitrogen in Paddy Field

Abstract

【Background】 Nonpoint source pollution from managed ecosystems is a major environmental concern in many countries. Using models to simulate contaminant movement in agricultural systems under different managements can help improve water management and reduce nitrogen loss. 【Objective】 The purpose of this paper is to study the movement and reaction of water and nitrogen in paddy field under different irrigation and drainage, with a view to improve water conservation and reduce gas emission from rice production in southern China. 【Method】 We used the DRAINMOD model to simulate water flow and nitrogen transport; the sensitivity of the simulated results to its parameters was quantified using the Morris analysis. 【Result】 Horizontal saturated hydraulic conductivity in the 20~40 cm soil layer affected the simulation results most; diffusion coefficient, denitrification and nitrification parameters, decomposition of soil organic matter all had a significant impact on the simulated nitrogen dynamics. The DRAINMOD model was able to simulate water and nitrogen dynamics in soil under different irrigations and drainages, and the difference between the simulated and measured drainage and irrigation amounts and the total load of nitrogen runoff was less than 11%. Compared with traditional irrigation and drainage, controlled irrigation and drainage reduced drainage amount by 33.0%~72.6%, irrigation amount by 9.7%~37.1%, ammonium runoff load by 43.6%~45.0%, and nitrate runoff load by 29.8%~53.1%. 【Conclusion】 Controlled irrigation and drainage can effectively reduce gas emission, drainage and nitrogen loss from the paddy field, and the DRAINMOD model is able to simulate water flow and contaminant transport in paddy fields under different irrigation and drainage managements.

Keywords

• rice
• change in water and nitrogen
• drainmod model
• sensitivity analysis
• controlled irrigation and drainage