Variable Rate Sprayer System for Citrus Orchards Using Tree Canopy Measurement with On-The-Go (OTG) Sensors

Pesticide application plays a key role in maintaining the quality of citrus orchards and helps protect them from various biological damages. Pakistan is the eleventh largest producer of citrus with 0.192 million hectares of area under citrus cultivation and an average production of 2.001 million tons. However, production and earning of citrus is much lesser when compared to the international standards. This is mainly due to the lack of best management practices. For instance, in Pakistan, agrochemicals are applied uniformly without considering inter and intra-field variability. In conventional system, the applicator opens the sprayer’s nozzles without considering the tree canopy which is not only less effective in heavy canopy trees but also result in over-use of expensive agrochemicals. The operator cannot halt the sprayer in gaps between trees in line. The Variable Rate Sprayer System (VRSS) is expected to achieve two objectives: (1) Reduce the wastage of expensive agrochemicals by halting the spray between trees, and (2) Apply an optimum amount of spray on each tree based on its canopy size. Measuring tree canopy however is a challenging task due to the irregular and inhomogeneous tree shapes. In this paper, we have proposed an ultrasonic sensors’ based approach to measure tree canopy size based on which a variable rate spraying system is developed. The basic components of the system include: Ultrasonic sensors, processing unit (microcontroller), flow control mechanism and nozzles. Stepper motors are used to control the sensors’ movement. Sensors measure the tree canopy size and pass it to the processing unit which activates the flow control module and set the nozzles’ opening all in real time. The proposed system applies the right amount of agrochemicals at the right time and place. This reduces the pest level below the economic threshold and will improve the agricultural production in Pakistan.