Water relations of citrus trees under partial root zone drying along with shading

Climate change and ever-increasing water use, along with water scarcity, reduces crop production. Thus, efficient water management, such as deficit irrigation and shading could resolve some of these shortcomings. In deficit irrigation with partial root zone drying (PRD), half of the root zone is irrigated and the other half is left unirrigated. This experiment was conducted with five treatments of (1) full irrigation, which trees received 100 percent of soil field capacity (FC), 2) two PRD treatments, which receiving 50 (PRD50) and 75% (PRD75) of FI and 3) two PRD treatments, such above which treats by shading nets(SHPRD50 and SHPRD75). Tukey's test was used to compare treatment’s means of stomatal conductance (gs), leaf relative water content (rwc), stem water potential (Ψst), and leaf temperature (Tl). Moreover, Regression analysis was done between the above factors and leaf to air vapor pressure difference. The results show that gs and rwc were higher in FI, PRD75 and SHPRD75 relative to stressed treatments of PRD50 and SHPRD50. The same trend was registered for Ψst and the lowest values were achieved by treatments receiving 50% of FI. Leaf temperatures in some measurement intervals were significantly higher in stressed treatments of PRD50 and SHPRD50. Water deficiency significantly reduced yield in stressed treatments of PRD50, while reversly, it increased fruit sloble salids in PRD50 and PRD75. Shading on PRD treatments increased fruit size and yield, Although this improvement was significant only for fruit diameter of SHPRD75 in comparison with PRD50.