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Subject: Soil and Water Engineering × End date: 2012 × Start date: 2010 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    SIMULATION OF SOIL MOISTURE MOVEMENT UNDER RICE FIELD
    (2010) Mahesh Chand Singh
    Soil moisture is a key variable in controlling the exchange of water and heat energy between the land surface and the atmosphere through evaporation and plant transpiration. A field study was conducted at Punjab Agricultural University, Ludhiana, 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 (June 5 (D1) and June 20 (D2)), two varieties (PAU-201 (V1) of 120 days duration and hybrid RH-257 (V2) of 90 days duration (from transplanting to harvest)) and two irrigation regimes (intermittent irrigation at 2-days drainage period (I1) and irrigation based on soil water suction (SWS) of 16 k Pa (I2)). During calibration, for both varieties the parameters Ks (saturated hydraulic conductivity) and n (fitting parameter) were found to be most sensitive in respect of the model output. The validation of model was done by comparing observed and simulated values of soil moisture content at different depths. The model performance in simulating soil moisture profiles was evaluated by comparing observed and simulated values using four parameters namely, RMSE, Absolute percentage error, correlation coefficient and model efficiency. The distribution of the soil moisture under field experiment and by model simulation at different growth stages agreed closely. In case of PAU-201 (V1), it was observed that the irrigation water applied in the treatment D1V1I1 was 44 mm higher than the treatment D2V1I1 and the irrigation water applied in the treatment D1V1I2 was also 44 mm higher than the treatment D2V1I2. In case of RH-257 (V2), the irrigation water applied in the treatment D1V2I1 was 44 mm higher than the treatment D2V2I1 and the irrigation water applied in the treatment D1V2I2 was 124 mm higher than the treatment D2V2I2. In case of PAU-201 (V1), the deep drainage loss in treatment D1V1I1 was 133 mm less than the treatment D2V1I1 and in treatment D1V1I2 it was 75 mm less than the treatment D2V1I2. In case of RH-257 (V2), the deep drainage loss in treatment D1V2I1 was 120 mm less than the treatment D2V2I1 and in the treatment D1V2I2 it was 46 mm less than treatment D2V2I2. During validation the absolute error varied from 2.19 to 13.21 percent, 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 percent. Thus, Hydrus-2D model can be successfully adopted for simulating soil moisture profiles under rice crop.