![]() Laser-PWM and Manual-PWM produced significantly lower airborne and ground spray drift losses inside and outside the orchard than Disabled-PWM, and these losses decreased significantly as the distance away from the first sprayed row increased. Airborne spray losses were determined by using nylon screens, mounted at five heights on each of seven poles distributed at different distances from the first sprayed row. Artificial targets (plastic plates and water sensitive papers) were placed under twelve trees randomly selected from four rows of the orchard to collect spray losses to the ground. Field tests in a two-year-old young apple orchard were conducted to investigate spray losses to the ground and in the air for an air-blast sprayer equipped with three spray systems: 1) manually controlled constant-rate system enabled with the PWM spray system (Manual-PWM), 2) laser-guided variable-rate system enabled with the PWM spray system (Laser-PWM) and 3) conventional constant-rate system with disabled PWM valves (Disabled-PWM). Pulse Width Modulated (PWM) solenoid valves can be used to control nozzle flow rates for precision spray applications to reduce pesticide use, thereby reducing environmental risk and production cost. ![]() Incorporation of these variables in precision spraying systems will optimize spray decisions and help reduce excessive agrochemical applications. Control of airflow during spraying is another important parameter that needs to be considered. Assessment of terrain is important when field elevation has significant variability. In addition, air jet velocity, travel speed, wind speed and direction, droplet size, and canopy characteristics need to be considered for successful droplet deposition by the spraying system. We conclude there is a critical need for appropriate sensing techniques that can accurately detect the target. This review provides a systematic summary of current technologies used for precision spraying in tree fruits and highlights their potential, briefly discusses factors affecting spraying parameters, and concludes with possible solutions to reduce excessive agrochemical uses. Precision spraying addresses these concerns by precisely and efficiently applying pesticides to the target area and substantially reducing pesticide usage while maintaining efficacy at preventing crop losses. However, inappropriate and excessive use of pesticides is a major rising concern. Pesticide applications are an essential part of current agriculture, enhancing cultivated crop productivity and quality and preventing losses of up to 45% of the world food supply. Reducing risk from pesticide applications has been gaining serious attention in the last few decades due to the significant damage to human health, environment, and ecosystems. © 2013 American Society of Agricultural and Biological Engineers. These results demonstrate that the variable-rate sprayer incorporating the innovative laser scanning technology reduced spray drift and off-target losses of pesticides, was environmentally sustainable, and was economically beneficial to growers. Compared to the constant-rate sprayers, the laserguided variable-rate sprayer reduced average spray losses on the ground by 68% to 90% and around tree canopies by 70% to 92%, reduced airborne spray drift by 70% to 100%, and most importantly, reduced the spray volume by 47% to 73%, while spray deposition quality inside the canopy for these sprayers was comparable. Spray deposits from spray drift and offtarget losses were collected within tree rows at ground level, above and behind the sprayed trees, in the spaces between trees, and from 3.2 m tall poles at 5, 15, and 35 m from the tree rows. ![]() ![]() ![]() FALLOUT 4 DISABLE WATER DRIFT FULLTests were conducted at three different growth stages: Trees just beginning to leaf (leafing), half foliage, and full foliage. This new sprayer, the same sprayer with the variable-rate function disabled, and a conventional constant-rate air-blast sprayer were tested for comparison of spray drift and off-target losses in an apple orchard. A new drift reduction technology incorporating laser scanning capabilities with a variable-rate air-assisted sprayer was developed to address these problems. Spray drift and off-target losses are inherent problems of conventional air-assisted sprayers consequently, their low efficiencies cause environmental pollution and public anxiety. ![]()
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