Influence of Foliar Cu Application Rate on Citrus Trees Water Dynamics.

Nutrient management practices may affect citrus trees water dynamics. The objective of this study was to determine the effect of copper (Cu) application rates effect on citrus water relation parameters including stomatal conductance and stem water potential (Ψstem). The study was initiated in June, 2016 on five-year old sweet orange (Citrus x sinensis (L.) Osbeck) trees located at Immokalee, FL, on a fine sand soil texture (Sandy, siliceous, hyberthermic Arenic Alaquods). Forty-eight trees were divided into twenty-four trees affected with HLB and twenty-four trees un-affected. Copper application rates including: 0x, 0.5x, 1x and 2x per tree replicated six times applied at intervals of 3 weeks intervals from July through October each year. The stomatal conductance was measured using the Licor 1600 steady state porometer during June, September and December 2016. Simultaneously, Ψstem was measured using a Portable Plant Water Status Console. Results indicated significant (α=0.05) changes in stomatal conductance with higher Cu rates. The average value of stomatal conductance measured increased by 10% under higher Cu rate (2x) compared to 0.5x rate. Indicating trees stress increase under higher Cu rates.