Evaluation of evapotranspiration-based irrigation controllers in a tropical fruit orchard in southern Florida

摘要

Agricultural irrigation is the largest use of freshwater in Florida accounting for 45% of the state's fresh water withdrawals. Increased water demand due to rapid population growth and environmental restoration requires additional water supplies. Water conservation in agriculture is one viable source of 'new water'. Evapotranspiration (ET)-based irrigation controllers were investigated in a carambola orchard irrigated with micro-jets with the objectives of : 1) evaluating the quantity of irrigation water applied using real-time ET controllers, historical ET data and typical practices to schedule irrigation, and 2) evaluating the effect of ET-based irrigation scheduling on stem water potential (V_s). The four treatments [1) real-time ET-based Toro-lntelli-Sense-612 controller, 2) historical ET-based Rain Bird ESP-12-LX-plus controller, 3) typical irrigation practice in south Florida based on set dates and times, and 4) non-irrigated trees] were replicated three times and evaluated for differences inwater applications and PHI_s responses. Results indicate that the quantities of waterapplied by ET-based treatments were significantly less (p<0.05) than that applied by the typical irrigation practice. The real-time ET controller yielded the highest water saving of 56% while the historical ET based controller saved 48% compared to the typical irrigation practice. Stem water potential for all treatments was above -1.0 MP and was not significantly different among treatments probably due to the ability of carambola trees to regulate water potential through osmotic adjustment and reductionofstomatal conductance. Hence, adoption of ET-based irrigation controllers resulted in water conservation without significantly affecting the physiological processes of the plant measured in this study.