The appropriate time for supplemental irrigation of rainfed fig trees by measuring leaf temperature, soil moisture and meteorological data

The aim of this study was to determine the appropriate time for supplementary irrigation rainfed fig trees in Estahban region, Fars province south of Iran using canopy and meteorological data. In a 2-year experiment, different water stresse levels were applied to rainfed Fig trees and soil moisture was measured at different time intervals. For determination of supplementary irrigation timing based on crop water stress index, soil moisture, the air and plant canopy temperature, were measured. The experiment treatments consisted of a control (without irrigation) and supplementary irrigation at water stress index of 0, 0.2, 0.4, 0.6, 0.8. In each treatment, irrigation was applied at a time when the water stress was just above the selected threshold. Trees were irrigated by tanker as the concentional method in this region. The results of the study showed that the maximum stress occurred in stress index of 0.6 in late July when the soil moisture was about 12%. In spring, the beginning of water stress period, was observed at soil moisture of 14%. Simple equations for predicting the onset of water stress with respect to rainfall and evaporation are presented, which can be used to determine the time of supplementary irrigation. A set of the water–yield relationships were also proposed.