Charts for guiding irrigation in real time

In order to adjust correctly the irrigation calendar to actual weather and water limiting conditions, farmers require guidelines to help them in their day to day decisions. In this paper a procedure is outlined to present such guidelines in the form of a single chart. On the chart information concerning the irrigation interval and irrigation duration is presented. Tables guide the user (i) to adjust the irrigation interval to the actual weather conditions throughout the growing season and (ii) to select the duration of the water application as a function of the characteristics of the irrigation system. In case of water shortage during a particular period, additional data informs the user on the sensitivity of the crop to water stress. An example is presented for drip irrigated tomatoes in the region of Tunis on a fluvisol.