ABSTRACT
The availability of irrigation water is diminishing in many parts of the world, which creates the need for optimization and increasing irrigation efficiency imperative. This was achieved in the past by irrigation scheduling, which covers two aspects; when to irrigate and how much water to apply. The main purpose of irrigation scheduling was to avoid harmful conditions of water stress and yet save irrigation water and other expenses in order to make water use most efficient. Higher efficiency of water use may still be attained, provided certain plant developmental stages are less sensitive to water deficit than others, so that restricting water supply during those stages may hardly affect productivity. Developmental stages of many crops, which are sensitive, and non-sensitive are outlined in another article.
