Using weather forecast data for irrigation scheduling under semi-arid conditions

A new methodology based on the use of weather forecast data from freely and easily accessible online information for determining irrigation scheduling has been developed. Firstly, reference evapotranspiration (ETo) was determined with a user-friendly procedure that does not require previous local calibration, knowledge of data acquisition or processing, or a nearby weather station. The comparison of ETo based on short-term (same-day) and long-term (6-day-ahead) weather forecast data with measured data for 50 locations in southern Spain during 2013-2014 season indicated that differences in ETo were relatively low with root-mean-square error (RMSE) equal to 0.65 and 0.76 mm d(-1), respectively. The procedure was tested for a wide range of weather conditions in the development of irrigation schedules and yield simulations for maize crop during 2013-2014 season. Irrigation water depths provided by irrigation schedules based on ETo obtained from daily and weekly forecasts and from measured data showed differences of around 1.5 and 0.9 %, respectively. Likewise, yield simulation with irrigation scheduling based on forecast and measured data provided equal averaged values, with a relative RMSE of below 5 %. This similarity of irrigation scheduling and yield estimation based on forecast and measured data has proved the optimal performance of the proposed approach.