Development and testing of an irrigation scheduling model

An irrigation scheduling model (ISM) consisting of a database management sy stem (DBMS), model base and graphical user interface (GUI) was developed fo r performing irrigation scheduling under various management options for bot h single and multiple fields. The ISM is based on a daily water balance app roach and uses climatological, crop and soil data as input. Depending on th e availability of climatological data, the model offers a choice of one or more methods of estimating reference evapotranspiration (ETo). The GUI is b ased on mouse-driven approach with pop-up windows, pull-down menus and butt on controls. The model was tested against field data and the CROPWAT model. The model-predicted soil moisture contents were compared with the field-me asured data for both single and multiple field cases. The two models, ISM a nd 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 a s compared to measured yield. The ISM is a flexible and user-friendly irrig ation-scheduling tool, which can be used for efficient use of irrigation wa ter. (C) 2000 Elsevier Science B.V. All rights reserved.