Development and testing of an irrigation scheduling model

An irrigation scheduling model (ISM) consisting of a database management system (DBMS), model base and graphical user interface (GUI) was developed for performing irrigation scheduling under various management options for both single and multiple fields. The ISM is based on a daily water balance approach and uses climatological, crop and soil data as input. Depending on the availability of climatological data, the model offers a choice of one or more methods of estimating reference evapotranspiration (ETo). The GUI is based on mouse-driven approach with pop-up windows, pull-down menus and button controls. The model was tested against field data and the CROPWAT model. The model-predicted soil moisture contents were compared with the field-measured data for both single and multiple field cases. The two models, ISM and CROPWAT, gave similar values of soil moisture but showed some variation after the second irrigation. For both the single- and multiple-field cases, simulated bean yield was slightly higher than measured yield. Also, except for the Turc method, all ETo estimation methods resulted in higher yield as compared to measured yield. The ISM is a flexible and user-friendly irrigation-scheduling tool, which can be used for efficient use of irrigation water.