Scheduling Maize Irrigation by Crop Water Stress Index (CWSI) in North of Isfahan

Nowadays, the world is facing increasing population and demand for food as well as shortage of fresh water supplies (Mangus et al., 2016). Deficit irrigation (DI) and urban wastewater utilization are two management solutions for the purpose of reducing fresh water consumption in agriculture. Due to the shortage of irrigation water resources and the increase of the area under cultivation, farmers in the northern part of Isfahan (viz., Borkhar), Iran, employ these two strategies. Precise irrigation planning could be of help in preventing water stress and optimum performance in plants. Water stress is considered one of the most important plant stresses, which is the most common and limiting factor for yield (Jackson et al., 1981; Scherrer et al., 2011; Zia et al., 2013). Since 1970, canopy temperature has been accepted as an indicator of water stress because plants under stress close their stomata for preserving water and reducing stomatal conduction, decreasing transpiration, and increasing leaf temperature (Ballester et al., 2013). One of the most reliable indicators is the crop water stress index (CWSI). Several studies have been conducted on irrigation scheduling using leaf surface temperature measurements. (Candogan et al., 2013; Orta et al., 2003). The difference in air temperature and leaf area was calculated from the difference in vapour pressure for different irrigation treatments in soybean and watermelon plants. Also, sorghum was studied by O’Shaughnessy et al. (2010) in different irrigation systems and the crop water stress index (CWSI) was calculated. Mangus et al. (2016) examined the water stress index of corn in four stages of plant growth; their results showed that in the third stage of corn growth (i.e., in the flowering stage), the surface temperature of the leaf was higher and that the plant used the most energy for cob growth and thus shrinking transpiration from the plant. Based on the aforementioned studies, this study sought to compute the water stress index (CWSI) under irrigation treatments in the climate of North Isfahan in order to identify the irrigation time.