Measurement and modelling of soil water dynamics under ridge tillage in paddy field

Tillage activity under water-flooded conditions leads to dispensable leaching and other environmental problems in normal paddy cropping systems. Ridge tillage changes the micro-topography of paddy fields, thus altering soil water distribution and movement compared with conventional tillage. The measurements were conducted from 2017 to 2019 under conventional tillage and ridge tillage. The soil water content data for ridge tillage and conventional tillage were collected at 0–10, 10–20, 20–30, 30–40, and 40–50 cm depths. While HYDRUS was adopted to simulate water balance, boundary flux, and water velocity. Each year, three varying paddy field water condition periods were chosen for data collection. During normal flooded periods, soil water content for ridge tillage was 0.41 cm3·cm−3 and was 14.6 % lower than that for conventional tillage at 0–10 cm. In unflooded conditions, soil water content for ridge tillage was 0.3 cm3·cm−3, which was 13.4 % higher than that for conventional tillage at 0–10 cm. The hydraulic parameters in HYDRUS were optimized along with initial value that was obtained from the inverse solution in the Rosetta Lite model. According to the HYDRUS simulation, ridge tillage reduced soil water percolation in rice paddies by an average of 49.6 % compared with conventional tillage. Under normal flooded conditions, percolation loss velocity was 1.03 cm·hr−1 for ridge tillage, which was 29.5 % lower than that for conventional tillage. Based on the HYDRUS simulation, the RT increased capillary rising ability compared with CT, and the immersion range was expanded by 25 % for RT compared to CT. In paddy fields, ridge tillage improved soil water-use efficiency by reducing leaching and increasing capillary water supply compared with conventional tillage. Ridge tillage increased rice yields and water use efficiency, which meets the current need for decreasing the leaching and percolation of water and nutrients in paddy fields. •Ridge tillage reduced soil water percolation in paddy flooded conditions.•Ridge tillage improved soil water supply in dry seasons.•The direction and velocity of water flow is changed by ridge tillage.