Key Technologies for an Orchard Variable-Rate Sprayer: Current Status and Future Prospects

Abstract

An orchard variable-rate sprayer applies the appropriate amount of plant protection products only where they are needed based on detection data from advanced sensors, a system that has attracted increasing attention. The latest developments in the detection unit, variable control unit, and signal-processing algorithm of the variable-rate sprayer are discussed. The detection of target position and volume is realized with an ultrasonic sensor, a laser scanning sensor, or other methods. The technology of real-time acquisition of foliage density, plant diseases and pests and their severity, as well as meteorological parameters needs further improvements. Among the three variable-flow-rate control units, pulse width modulation was the most widely used, followed by pressure-based, and variable concentration, which is preliminarily verified in the laboratory. The variable air supply control unit is tested both in the laboratory and in field experiments. The tree-row-volume model, the leaf-wall-area model, and the continuous application mode are widely used algorithms. Advanced research on a variable-rate sprayer is analyzed and future prospects are pointed out. A laser-based variable-rate intelligent sprayer equipped with pulse width modulation solenoid valves to tune spray outputs in real time based on target structures may have the potential to be successfully adopted by growers on a large scale in the foreseeable future. It will be a future research direction to develop an intelligent multi-sensor-fusion variable-rate sprayer based on target crop characteristics, plant diseases and pests and their severity, as well as meteorological conditions while achieving multi-variable control.

Spray performance of flexible shield canopy opener and rotor wind integrated boom‐sprayer application in soybean: effects on droplet deposition distribution

“…3,4 However, the current spraying methods result in most pesticide droplets being intercepted by the soybean surface branches and leaves. 5 This causes uneven deposition of droplets in the soybean canopy, resulting in ineffective control of pests and diseases. Meanwhile, when spraying in the field, fine droplets can easily drift from the target by surrounding airflow.…”

Design and experimental assessment of a field‐spraying system with nozzles employing reciprocating up‐and‐down movements

“…7,8 Many researchers have studied air-assisted boom sprayers. 9 However, some results of these studies also showed that when the airflow passes through a dense crop canopy, the kinetic energy is significantly reduced, resulting in uneven deposits of droplets. 10 The droplet deposits in the middle and bottom of the crop canopy require further improvement.…”

“…The penetration and deposition of droplets are increased, and the environmental risk due to spray drift phenomenon is reduced 7,8 . Many researchers have studied air‐assisted boom sprayers 9 . However, some results of these studies also showed that when the airflow passes through a dense crop canopy, the kinetic energy is significantly reduced, resulting in uneven deposits of droplets 10 .…”

Research on decoupled air speed and air volume adjustment methods for air-assisted spraying in orchards

“…The global fruit industry has become the third-largest agricultural planting industry after the grain and vegetable industries. By 2020, the area of orchards in China had reached 1.33×10 7 hm 2 (Zheng et al, 2020;Wei et al, 2023), ranking first in the world. Orchard pest control has long relied on chemical pesticides.…”