Irrigation Scheduling and Watermelon Yield Model for the Jordan Valley

A crop yield and soil water management simulation model (CRPSM) developed at Utah State University was modified, calibrated and tested using local weather data and field results from a trickle irrigation experiment with different mulching on watermelon ( Citrullus lanatus ), carried out at the University of Jordan Research Station, in the Jordan Valley.
Simulated irrigation schedules were then applied with some of the four options provided by the model. The water yield index, WYI, introduced by B attikhi and H ill (1985) to select the most efficient schedule as based on yield and water use efficiency, was then determined. WYI ranged from 27 to 87. The field schedule, WM₂, had a WYI of 62. Whereas, the model provided a much better schedule, WM₇ (WYI = 86). WM₇ requires 17 irrigations of 2.0 cm per irrigation totaling a water supply of 44.1 cm with an irrigation season starting on April 7 to give a yield equivalent to the potential yield, 80.0 MT/ha. On the other hand, the best field schedule, WM₂ under transparent mulch, required 14 irrigations to provide 45.9 cm (including rainfall and soil moisture change), with a season starting on April 28 resulted in a yield of 68.8 MT/ha. So we can see that by using the same amounts of total water supply but with different schedule we can get the potential yield. The model has, therefore, provided few better schedules that can be tested in the field at lower costs before final recommendations are made.