The State of Current Knowledge
The basic processes of crop evapotranspiration (ET) for crop production under either optimum or water-deficit crop production scenarios are well understood. In addition, real-time weather and other important meteorological data is relatively simple and affordable to obtain from modern electronic instrumentation. Improved irrigation scheduling practices are based on developing reference ET values from reference crops (such as grass or alfalfa) that are produced in lysimeters, along with using empirical coefficients derived from the real-time meteorological measurements. The models that calculate the reference ET values and estimate the actual crop water requirements are based on derivatives of the well-known Penman equation. Through them, actual irrigation scheduling practices, the centerpiece of the IMIS program, are fitted or tailored to specific localized crop, soil, and climatic conditions.
The general crop coefficients have been developed for the major field and orchard crops in Israel and IMIS increasingly is being disseminated as a mainstream agricultural production practice. Fax, phone and Internet conveys information on crop ET and recommends water delivery amounts to the growers. However, only a limited amount of information is being provided to the growers of specialized or higher-valued fruit and vegetable crops throughout Israel. In Jordan and the Palestinian Authority (PA) there is almost no research, training, delivery, or acceptance of an IMIS program.