Abstract

Soil moisture is a key variable in controlling the exchange of water between land surface and atmosphere through evaporation and plant transpiration. A field study was conducted at Punjab Agricultural University, Ludhiana (India), in the year 2009, to simulate the soil moisture movement under rice field using numerical model Hydrus-2D. The treatments included two dates of transplanting viz., June 5 (D1 and June 20 (D2), two varieties inbred PAU-201 (V1 and hybrid RH-257 (V2) of 120 and 90 days durations (from transplanting to harvest) and two irrigation regimes viz., intermittent irrigation at 2-days drainage period (I1) and irrigation based on soil water suction (SWS) of 16 k Pa (I2). A total of eight treatments were replicated thrice in 24 plots of each having size 10 x 4 m. The saturated hydraulic conductivity (Ks varied from 0.36 to 1.48 cm/day with an average value of 0.92 cm/day) and the fitting parameter (n varied from 1.58 to 2.76 with an average value of 2.17) were found to be very sensitive during calibration. The results from the experiment revealed that the soil moisture content was more in upper layer of the soil profile as compared to the lower layers due to effect of puddling. The application of Hydrus-2D confirmed that the simulated depth wise soil moisture content values were in good agreement with observed data. The model performance was evaluated by using parameters, namely, root mean square error, absolute percentage error, correlation coefficient and model efficiency. During validation, the average absolute error varied from 2.19 to 13.21%, root mean square error varied from 0.006 to 0.032 cm, correlation coefficient varied from 0.773 to 0.996 and the average model efficiency was 98.6%. The use of Hydrus-2D model can be successfully adopted for simulating soil moisture profiles under rice crop.