Abstract:
HYDRUS-1 D model is one of the advanced lumped/distributed models applied in simulation of water flow, moisture distribution and solutes transport in unsaturated zone (between soil surface and water table). In this study, the model was used to simulate soil water dynamics under overhead irrigation system during garlic and pepper crops growth. The study was conducted in Dangila, Dengeshita watershed at plot level. The treatments were consisted of conservation agriculture (CA) and conventional tillage (CT) plots. The irrigation depth, crop phenology, meteorological and soil hydraulic parameters were used as input data to Hydrus-1D model. Soil hydraulic parameters were estimated from easily measured soil physical properties using KNN pedotransfer functions for tropical soils and then fitted using Retention curve optimization program (RETC). Two experiments were carried out from October-February 2017/2018 (garlic growing season) and March - June 2018 (pepper growing season) period. The model performance was evaluated by comparing the observed and simulated daily soil water content values both at CA and CT experimental plots. The results showed good agreement between the observed and simulated soil water content (SWC) with high R2 (0.64-0.77) and low error (RMSE of 0.021-0.063, ME of 0.0013 – 0.040) values. The model accuracy was good for CT rather than CA experimental plots. The overall evaluation according to the common performance evaluation techniques revealed that the observed and simulated SWC in CA plots was higher compared to those in CT plots. According to t-test: two sample assuming equal variance statistical analysis result the SWC variations between CA and CT plots was significant. The simulated seasonal actual transpirations and deep percolations were lower in CT plots due to higher evaporation loss during the simulation period; even the difference was insignificant statistically. The model result concludes that CA was better than CT due to store more water and to reduce soil evaporation.