Development of Deep Learning-Based Variable Rate Agrochemical Spraying System for Targeted Weeds Control in Strawberry Crop

Agrochemical application is an important tool in the agricultural industry for the protection of crops. Agrochemical application with conventional sprayers results in the waste of applied agrochemicals, which not only increases financial losses but also contaminates the environment. Targeted agrochemical sprayers using smart control systems can substantially decrease the chemical input, weed control cost, and destructive environmental contamination. A variable rate spraying system was developed using deep learning methods for the development of new models to classify weeds and to accurately spray on desired weeds target. Laboratory and field experiments were conducted to assess the sprayer performance for weed classification and precise spraying of the target weeds using three classification CNNs (Convolutional Neural Networks) models. The DCNNs models (AlexNet, VGG-16, and GoogleNet) were trained using a dataset containing a total of 12,443 images captured from the strawberry field (4200 images with spotted spurge, 4265 images with Shepherd’s purse, and 4178 strawberry plants). The VGG-16 model attained higher values of precision, recall and F1-score as compared to AlexNet and GoogleNet. Additionally VGG-16 model recorded higher percentage of completely sprayed weeds target (CS = 93%) values. Overall in all experiments, VGG-16 performed better than AlexNet and GoogleNet for real-time weeds target classification and precision spraying. The experiments results revealed that the Sprayer performance decreased with the increase of sprayer traveling speed above 3 km/h. Experimental results recommended that the sprayer with the VGG-16 model can achieve high performance that makes it more ideal for a real-time spraying application. It is concluded that the advanced variable rate spraying system has the potential for spot application of agrochemicals to control weeds in a strawberry field. It can reduce the crop input costs and the environmental pollution risks.

Variable rate spraying

n this topic, the principles of the modulation of the pesticide dose (liters or kilograms put ion the crop, per hectare) will be explained. Consequences on pest control, cost and final crop yield. Advantages and disadvantages of the application of such technologies, along with the electronics systems abroad the machinery, capable of performing such variable dosing will be presented.

Research Progress on Variable-Rate Spraying Technology in Orchards

HighlightsReview the research status of variable-rate spraying technology and point out the direction for the future researchDiscussed the advantages and disadvantages of different techniques to detect canopy volume and canopy biomassThe air speed and volume adjustment need to be controlled based on the canopy detection systemAbstract. Variable-rate pesticide application in orchards aims to solve the problems of low pesticide utilization rates and serious environmental pollution in traditional pesticide applications. In this article, we have reviewed the research status of the technology to point out the direction for future research. Orchard tree canopy volume detection, biomass detection, and variable-rate spraying control methods were systematically summarized and analyzed. The advantages and disadvantages of different sensing techniques for detecting canopy volume and canopy biomass have been discussed. Canopy volume is mainly detected by ultrasonic sensors and light detection and ranging (LiDAR) sensors. Canopy biomass detection can be realized by manual, ultrasonic sensors, LiDAR sensors, and other sensors. Variable-rate spraying control is in two parts: liquid flow rate regulation and air supply rate regulation. In order to determine the volume of the liquid variable-spray, the variable air supply of air-assisted sprayer has been proven to be important. Liquid flow regulation can be achieved by pipeline pressure control and nozzle flow rate control together with a series of algorithms. The direction of air supply is easy to determine, but the air speed and volume adjustment need to be controlled based on the canopy detection system. Finally, future research on variable-rate spraying technology should focus on: 1) the application of advanced sensing technology for accurate and real-time measurement of canopy volume and biomass, 2) accurate control algorithms for liquid flow rate regulation and methods for airflow regulation, and 3) design of variable-rate sprayers with both liquid and air regulations, and the establishment of different types of variable-rate models for different sprayer types. Keywords: Air supply rate regulation, Canopy biomass detection, Canopy volume detection, Liquid flow rate regulation, Orchard, Variable-rate spraying.

Investigation of an Experimental Laser Sensor-Guided Spray Control System for Greenhouse Variable-Rate Applications

Precision variable-rate spraying technology is needed for controlled-environment plant production in greenhouses. An experimental spray system for greenhouse applications was developed for real-time control of individual nozzle outputs. The system mainly consisted of a high-speed laser scanning sensor, 12 individual variable-rate nozzles, an embedded computer, a spray control unit, and a 3.6 m long mobile spray boom. Each nozzle was coupled with a pulse-width modulated solenoid valve to discharge sprays at variable rates based on target presence and plant canopy structure. Laboratory tests were conducted to evaluate the accuracy of the spray control system in respect to spray delay time, nozzle activation, and spray volume using four target objects of different regular geometrical shapes and surface textures and two artificial plants of different canopy structures. Other experimental variables included three detection heights from 0.5 to 1.0 m and five sensor travel speeds from 1.6 to 4.8 km h-1. A high-speed video camera was used to determine the delay time and nozzle activation in discharging sprays on target objects after the laser sensor had detected the objects. The detection height and travel speed were found to have slight influence on the timing of nozzle activation. The nozzles started spraying in a range between 33 and 83 mm before reaching the target objects and stopped spraying between 13 and 84 mm after passing the objects, ensuring that the objects were fully covered by the spray. Spray volume corresponded to the object sizes well, and the spray control system performed with higher accuracy at lower travel speeds. Differences between the calculated spray volume based on the sensor detection and the actual spray volume ranged from 1.9 to 2.7 mL per object among all tested objects. The variable-rate control system reduced spray volume by 29.3% to 51.4% for all the objects compared with conventional constant-rate spraying. At the same time, the nozzles could be activated precisely by the object presence. Consequently, this experimental laser-guided system was implemented on a boom system in a commercial greenhouse for future investigations of its accuracy in variable-rate spraying to save pesticides, water, and nutrients. Keywords: Automation, Intelligent sprayer, Pesticide, Precision spray technology, Boom spray equipment.