Variable-rate Sprayer Research Articles

Predicting the site-specific distribution of agrochemical spray deposition in vineyards at multiple phenological stages using 2D LiDAR-based primary canopy attributes

Predicting the dose to be applied on the basis of the structural characteristics of the plant canopy is a crucial step for the optimization of the spraying process. Mobile 2D LiDAR sensor data and local measurements of deposition rates from a face-to-face sprayer were made across eight fields in two Mediterranean vineyards at four dates in 2016 and 2017. Primary canopy attributes (height, width and density) were calculated from the LiDAR sensor data and the leaf wall area (LWA) determined. Multivariate models to predict the deposition distribution, as deciles, as a function of the primary canopy attributes were constructed and calibrated using the 2017 data and validated against the 2016 data. The prediction quality and uncertainty of these multivariate statistical models at various stages of growth was evaluated by comparison with a previously proposed univariate deposition models based on LWA at the same growth stages. The results showed that multivariate models can predict the distribution of deposits from a typical face-to-face sprayer more accurately (0.76 < R2 < 0.94), and robustly (10% < nRMSEp < 24%) than LWA-based univariate prediction models over the whole growing season. This improvement was especially clear for the lowest deciles (D1 to D5) of the deposition distribution. Results also demonstrated the importance of canopy density to provide relevant and complementary information to canopy dimensions when predicting deposition deciles with the multivariate models. The improved ability of multivariate models to predict underestimated deposition (−1.5% < bias < −3.2%) when compared to univariate models makes it possible to consider a reduction in the plant protection products while guaranteeing a safety margin for winegrowers when spraying. These predictive multivariate models could enable variable-rate sprayers to modulate doses at an intra-plot scale, which would allow a potential reduction in the quantities of plant protection products to be applied.

Field assessment of a pulse width modulation\xa0(PWM) spray system applying different spray volumes: duty cycle and forward speed effects on vines spray coverage

The pulse width modulation (PWM) spray system is the most advanced technology to obtain variable rate spray application without varying the operative sprayer parameters (e.g. spray pressure, nozzle size). According to the precision agriculture principles, PWM is the prime technology that allows to spray the required amount where needed without varying the droplet size spectra which benefits both the uniformity of spray quality and the spray drift reduction. However, some concerns related to the effect of on–off solenoid valves and the alternating on/off action of adjacent nozzles on final uneven spray coverage (SC) have arisen. Further evaluations of PWM systems used for spraying 3D crops under field conditions are welcomed. A tower-shaped airblast sprayer equipped with a PWM was tested in a vineyard. Twelve configurations, combining duty cycles (DC: 30, 50, 70, 100%) and forward speeds (FS: 4, 6, 8 km h−1), were tested. Two methodologies, namely field-standardized and real field conditions, were adopted to evaluate the effect of DC and FS on (1) SC variability (CV%) along both the sprayer travel direction and the vertical spray profile using long water sensitive papers (WSP), and (2) SC uniformity (IU, index value) within the canopy at different depths and heights, respectively. Furthermore, the SC (%) and deposit density (Nst, no stains cm−2), determined using short WSP, were used to evaluate the spray application performances taking into account the spray volumes applied. Under field-controlled conditions, the pulsing of the PWM system affects both the SC variability measured along the sprayer travel direction and along the vertical spray profile. In contrast, under real field conditions, the PWM system does not affect the uniformity of SC measured within the canopy. The relationship between SC and Nst allowed identification of the ranges of 200–250 and 300–370 l ha−1 as the most suitable spray volumes to be applied for insecticide and fungicide plant protection products, respectively.

Variable-rate Spray Technology Optimizes Pesticide Application by Adjusting for Seasonal Shifts in Deciduous Perennial Crops

To optimize pesticide applications to the canopies of deciduous perennial crops, spray volume should be adjusted throughout the year to match the changes in canopy volume and density. Machine-vision, computer-controlled, variable-rate sprayers are now commercially available and claim to provide adequate coverage with decreased spray volumes compared with constant-rate sprayers. However, there is little research comparing variable- and constant-rate spray applications as crop characteristics change throughout a growing season. This study evaluated spray volume, spray quality (e.g., coverage and deposit density), and off-target spray losses of variable- and constant-rate sprayers across multiple phenophases in an apple (Malus domestica) orchard and a grape (Vitis vinifera) vineyard. The variable-rate sprayer mode applied 67% to 74% less volume in the orchard and 61% to 80% less volume in the vineyard. Spray coverage (percent), measured by water-sensitive cards (WSC), was consistently greater in the constant-rate mode compared with the variable-rate mode, but in many cases, excessive coverage (i.e., over-spray) was recorded. The variable-rate sprayer reduced off-target losses, measured by WSC coverage, up to 40% in the orchard and up to 33% in the vineyard. Spray application deposit densities (droplets per square centimeter) on target canopies were typically greater in variable-rate mode. However, the deposit densities were confounded in over-spray conditions because droplets coalesced on the WSC resulting in artificially low values (i.e., few, very large droplets). Spray efficiencies were most improved early in the growing season, when canopy density was lowest, demonstrating the importance of tailoring spray volume to plant canopy characteristics.

Improved Canopy Characterization with Laser Scanning Sensor for Greenhouse Spray Applications

HighlightsAn algorithm was developed to process laser sensor data to make more accurate measurements of canopy dimensions.The algorithm isolated individual canopies, removed distortion, and estimated the occluded portions of the dataset.The algorithm reduced measured error by 46% in terms of root mean square error (RMSE).The RMSE was higher for sensor heights below and above a calculated optimal sensor height.Abstract. Laser-guided intelligent spray technology for greenhouse applications requires sensors that can accurately measure plant dimensions. This study proposed a new method to overcome current limitations by introducing a processing algorithm that manipulates the noisy dataset and determines the optimal sensor height to produce better measurements of the canopy width. The processing algorithm involves a combination of registration, clustering, and mirroring. Registration aligns multiple scans of the same scene to improve resolution. Clustering isolates individual plant canopies from the dataset to enable further processing. Mirroring is used to resolve the problems of distortion and occlusion and predict missing information in the dataset. The performance of the processing algorithm was evaluated by calculating the root mean square error (RMSE) in the canopy width measurements. Its results were compared with the measurements reported in earlier research, where there was limited processing of the laser sensor data. The processing algorithm reduced RMSE values by 46% compared to the earlier research, and the largest improvements were seen for objects placed beyond 1.5 m from the sensor. The sensor height was observed to be inversely proportional to the RMSE values. The average RMSE of the processing algorithm was 25 mm, compared to 47 mm in the earlier research when the laser sensor was at a height of 1 m. Another experimental setup was used to test the limits of the relationship between sensor height and algorithm performance while using objects that were more representative of plant canopy shapes. The accuracy of the processing algorithm decreased when the sensor height was either above or below the optimal sensor height, which was derived from calculations made in earlier research. The processing algorithm has potential to improve spray efficiencies. Keywords: Automation, Clustering, LiDAR, Point cloud data processing, Variable-rate spray.

Droplet Size Spectrum, Activation Pressure, and Flow Rate Discharged from PWM Flat-Fan Nozzles

HighlightsDroplet sizes, activation pressures acting on nozzle orifices, and flow rates were investigated.Droplet sizes varied with duty cycles, nozzle orifice sizes, and PWM solenoid valve manufacturers.Activation pressures decreased as duty cycles decreased and increased as nozzle orifice sizes decreased.Flow rates increased with increases in both duty cycles and nozzle orifice sizes.Abstract. Pulse width modulated (PWM) spray systems can produce variable spray rates for precision applications of pesticide and fertilizer; however, there are also concerns over their spray performance stability. Droplet size distributions, activation pressures acting on nozzle orifices, and flow rates discharged from nozzles were investigated for test combinations of ten PWM duty cycles (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%), six flat-fan nozzles with different orifice sizes (XR8001, XR8002, XR8003, XR8004, XR8005, and XR8006), and two PWM solenoid valves from two different manufacturers. Test results showed that the droplet size distribution, activation pressure, and flow rate varied with the duty cycle, nozzle orifice size, and PWM solenoid valve source. For XR8001 and XR8002 nozzles, droplet sizes did not vary significantly with all duty cycles from 10% to 100%. To obtain relatively consistent droplet size distributions, XR8003 and XR8004 nozzles required PWM duty cycles of at least 20%, while XR8005 and XR8006 nozzles required duty cycles of 30% or greater. The activation pressure directly on nozzle orifices increased as the duty cycle increased but decreased as the nozzle orifice size increased. In addition, the same nozzles coupled with PWM solenoid valves from two different manufacturers discharged different flow rates for the same duty cycle in the range of 10% to 90%. Therefore, careful selection of PWM solenoid valves for different orifice nozzles operated at different duty cycles was necessary to achieve consistent variable-rate spray performances. Keywords: Droplet diameter, Variable rate, PWM solenoid valve, Pesticide, Fertilizer, Precision farming.

Design and Development of a Smart Variable Rate Sprayer Using Deep Learning

The uniform application (UA) of agrochemicals results in the over-application of harmful chemicals, increases crop input costs, and deteriorates the environment when compared with variable rate application (VA). A smart variable rate sprayer (SVRS) was designed, developed, and tested using deep learning (DL) for VA application of agrochemicals. Real-time testing of the SVRS took place for detecting and spraying and/or skipping lambsquarters weed and early blight infected and healthy potato plants. About 24,000 images were collected from potato fields in Prince Edward Island and New Brunswick under varying sunny, cloudy, and partly cloudy conditions and processed/trained using YOLOv3 and tiny-YOLOv3 models. Due to faster performance, the tiny-YOLOv3 was chosen to deploy in SVRS. A laboratory experiment was designed under factorial arrangements, where the two spraying techniques (UA and VA) and the three weather conditions (cloudy, partly cloudy, and sunny) were the two independent variables with spray volume consumption as a response variable. The experimental treatments had six repetitions in a 2 × 3 factorial design. Results of the two-way ANOVA showed a significant effect of spraying application techniques on volume consumption of spraying liquid (p-value &lt; 0.05). There was no significant effect of weather conditions and interactions between the two independent variables on volume consumption during weeds and simulated diseased plant detection experiments (p-value &gt; 0.05). The SVRS was able to save 42 and 43% spraying liquid during weeds and simulated diseased plant detection experiments, respectively. Water sensitive papers’ analysis showed the applicability of SVRS for VA with &gt;40% savings of spraying liquid by SVRS when compared with UA. Field applications of this technique would reduce the crop input costs and the environmental risks in conditions (weed and disease) like experimental testing.

Management of Pest Insects and Plant Diseases in Fruit and Nursery Production with Laser-guided Variable-rate Sprayers

Laser-guided variable-rate intelligent spray technology is anticipated to reduce pesticide use in production of crops and safeguard the environment. However, the ability of this technology to effectively control insect pests and diseases of crops must be validated before it becomes part of integrated pest management programs. Abilities of three different intelligent sprayers were tested to control pest insects and plant diseases at one fruit farm and two ornamental nurseries in Ohio during three consecutive growing seasons. The same sprayers with disabled intelligent functions were used as conventional constant-rate applications for comparisons. Test crops were apple (Malus pumila), peach (Prunus persica), blueberry (Vaccinium sect. Cyanococcus), black raspberry (Rubus occidentalis), crabapple (Malus sp.), maple (Acer sp.), birch (Betula sp.), and dogwood (Cornus florida). There were five insects and six diseases total involved in the investigations in the fruit farm and two nurseries. The field tests showed the intelligent spray applications reduced pesticide and foliar fertilizer use by ≈30% to 65% on average during the 3-year experiments. At the same time, intelligent spray technology was similar or more effective than conventional spray technology when controlling insects and diseases on a variety of crops. These results demonstrated that intelligent spray technology was environmentally friendly and more effective for control of insect and disease pests in fruit farms and ornamental tree nurseries.

Evaluation of the Intelligent Sprayer System in Peach Production.

Air-blast sprayers are routinely used to apply pesticides in commercial peach orchards, with growers using both conventional air-blast and ultrasonic sensor-driven models. Even with advanced spray technologies, there are still concerns with the amount of chemicals used and lost to drift. Our study evaluated a laser sensor-based variable-rate sprayer system in three experimental peach orchards for pest and brown rot disease control, spray volume output, spray coverage, and spray drift. A single 378-liter air-blast sprayer was used for both the conventional air-blast and the Intelligent Sprayer (iSprayer) treatments. Treatments were started at the phenological stage of bloom and continued through final swell. The iSprayer treatment was as effective in controlling pests and brown rot disease as the conventional air-blast treatment. Compared with the conventional air-blast treatment, the iSprayer treatment reduced the spray volume (liters/hectare) in cultivar PF23 by 71% at bloom, 62% at pit hardening, and 55% at final swell. For Juneprince, the spray volume reduction was 50% at bloom, 40% at pit hardening, and 13% at final swell. Spray drift was significantly (P < 0.05) reduced only at bloom in the iSprayer treatment. Spray coverage was increased by 50.13 and 26.67% in the iSprayer treatment at bloom and pit hardening, respectively, but not at final swell. Our results show that the iSprayer maintained pest and disease control efficacy in peach orchards while reducing spray volume and drift compared with the conventional air-blast treatment.

Advancing Sustainability in Tree Crop Pest Management: Refining Spray Application Rate with a Laser-guided Variable-rate Sprayer in Apple Orchards

Advanced variable-rate spray technology, which applies pesticides based on real-time scanning laser rangefinder measurements of plant presence, size, and density, was developed and retrofitted to existing sprayers. Experiments were conducted to characterize the application of four programmed spray rates (0.03, 0.05, 0.07, or 0.09 L·m−3 of crop geometric volume) when applied to Malus domestica Borkh. ‘Golden Delicious’ apple trees using this crop sensing technology. Water-sensitive cards (WSCs) were used as samplers to quantify spray coverage, deposits, and deposit density in the target and nontarget areas, and an overspray index based on a threshold of greater than 30% coverage was calculated. The application rate ranged from 262 L·ha−1 at the programmed spray rate of 0.03 L·m−3 to 638 L·ha−1 at the rate of 0.09 L·m−3. For a given WSC position, spray coverage and deposits increased as the spray rate increased. WSC positions 1 and 2 were oversprayed at all rates. The effect of spray rate on deposit density varied with WSC positions, with high densities achieved by low spray rates for WSCs closest to the sprayer but by high spray rates for WSCs positioned either deeper within or under the canopy. When coalescing deposits were accounted for, deposit densities met or exceeded the recommended pesticide application thresholds (insecticides 20–30 droplets/cm2; fungicides 50–70 droplets/cm2) at all WSC positions for each spray rate tested. The lowest spray rate reduced off-target loss to the orchard floor by 81% compared with the highest rate, dramatically reducing potential exposure to nontarget organisms, such as foraging pollinators, to come into contact with pesticide residues. Applying the lowest rate of 0.03 L·m−3 met deposit density efficacy levels while reducing spray volume by 83% compared with the orchard standard application of 1540 L·ha−1 and by 87% compared with the 1950 L·ha−1 application rate recommended when using the tree row volume method. Thus, there is potential for growers to refine pesticide application rates to further achieve significant pesticide cost savings. Producers of other woody crops, such as nursery, citrus, and grapes, who use air-assisted sprayers, may be able to achieve similar savings by refining pesticide applications through the use of laser rangefinder-based spray application technology.

Different sensor based intelligent spraying systems in Agriculture

Chemical application of nutrients and pesticides is one of the most important processes in agricultural production, but also one of the most dangerous agricultural operations. To improve the chemical efficacy, reduce chemical and labor costs, minimize labor hazards, and reduce the harmful environmental damage. Variable-rate spray applications that use intelligent control systems can significantly reduce pesticide use and off-target environmental pollution. Real-time variable-rate spraying technology offers effective and efficient use of pesticides. The variable-rate spray allows the farmers to apply pesticides only on the target, using only the correct amount based on the canopy size, season, and growth phase of the plants. In the past few decades, target detection systems have been developed using advanced methods such as laser and vision scanning systems or, more simply, ultrasound, infrared, and spectrum systems. Real-time target detection spray Systems used for the detection of the geometric properties of tree plants are reviewed in detail. Among these methods, machine vision and laser scanners systems are possibly the most capable and complementary means of obtaining three-dimensional images and maps of plants and canopies. This paper discusses a review of various sensing technologies available for the determination of canopy structural parameters and discusses how they are used for precision spraying. Some of the challenges and considerations of the use of these sensors and technologies are also discussed.

Assessment of chemical concentration accuracy and mixture uniformity of premixing in-line injection system

A premixing in-line injection system was developed and attached as a retrofit to a laser-guided variable-rate orchard sprayer. Chemical concentration accuracy and spray mixture uniformity produced from the premixing system was investigated with various viscosities of simulated pesticides and duty cycles of pulse-width-modulated (PWM) nozzles at different positions on the sprayer. The chemical concentration accuracy was accessed by calculating the relative error (RE) between measured and target concentrations, and mixture uniformity was evaluated by the coefficient of variation (CV) of the mixture concentration. Test results showed that the measured concentration was consistent across different nozzle positions, and RE and CV were observed within desirable ranges (<5.0%) for all nozzle positions and target concentrations. The average measured concentration slightly decreased as the viscosity of simulated pesticides increased. This phenomenon was more obvious under higher target concentrations. In addition, effects of PWM duty cycle combinations on the chemical concentration accuracy and mixture uniformity varied with number of active nozzles. It was found that RE and CV were larger than the desirable level (greater than5.0%) but were lower than the acceptable level (<10.0%) under conditions that nozzles were partly activated. For other treatments which all nozzles were activated, RE and CV were under the desirable level (<5.0%) for all target concentrations and nozzle positions. Laboratory tests demonstrated that the premixing in-line injection system was able to adequately mix the simulated pesticides with water, and could provide accurate and consistent uniformity of spray mixtures for the variable-rate spray nozzles to discharge different viscosities of simulated pesticides at different duty cycle combinations.

Techno-economic impacts of using a laser-guided variable-rate spraying system to retrofit conventional constant-rate sprayers

Specialty crops, such as apples, are vulnerable to insects and pathogens, and require higher pesticide input than row crops, a significant fraction of which is off-target loss, causing adverse environmental and socio-economic impacts. An advanced laser-guided variable-rate sprayer (VRS) could improve spray deposition uniformity and minimize pesticide waste, while maintaining efficacy against insects and pathogens. Despite these merits, retrofitting a conventional sprayer with laser-guided variable-rate spraying functions adds to its cost. Thus, the objective of this study was to analyze the techno-economics of a conventional pesticide sprayer retrofitted with VRS, in comparison to a conventional constant-rate sprayer (CRS) for pesticide application during apple production. A techno-economic model was developed for the apple orchards covering areas of 4 and 20 ha, which are common orchard sizes in the USA. The model incorporated cost for operation, equipment, fuel use and labor during pesticide application. The data were obtained from field tests in orchards in Ohio, USA in years 2016 and 2017, literature, and the original VRS development team at USDA-ARS and Ohio State University. The results indicated that VRS can reduce pesticide costs by 60–67%, pesticide application time by 27–32% and labor and fuel by 28% compared to CRS. For larger orchards, VRS also reduced equipment requirement. Compared to CRS, overall annual pesticide application cost savings by using VRS were between $1420 and $1750 ha−1. The payback time for using VRS was estimated to be between 1.1 and 3.8 years for apple orchards between 4 and 20 ha, respectively, in Ohio.

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.

A Low-Cost Prototype to Automate Agricultural Sprayers

The world’s population growth in the last decades demanded a great increase in agricultural production, especially in food. Therefore, in order to reduce possible losses and guarantee productivity, farmers depend more and more on the application of agrochemicals in their crops. This massive use of pesticides represents not only a high cost to the farmers but also a risk to their health, to the environment and even to the safety of the food consumed by the population. In this context, new technologies have been developed to make agricultural spraying more effective, reducing the amount of pesticide applied and dosing its use according to the need of the crop. The recognition of its spatial and temporal variability is treated by Precision Agriculture. In the case of pest management it can be done using variable-rate sprayers or using on/off application with individual nozzle control. Thus, this paper proposes a low-cost prototype in a modular solution to automate existent agricultural sprayers. The solution allows individual nozzle opening, with on/off control, using solenoid valves, pressure and flow sensors, Arduino boards, and smartphone. Additionally, the prototype has a data logger function to store nozzle status and sensor values, allowing future analysis and application reports.

Hardware and Software Design for Premixing In-Line Injection System Attached to Variable-Rate Orchard Sprayer

.HighlightsA premixing in-line injection system was designed as a retrofit attachment to a laser-guided variable-rate orchard sprayer.A graphical user interface with touchscreen functions was incorporated into the system to facilitate field applications.Preliminary tests demonstrated that simulated pesticide and water could be accurately dispensed and discharged separately into the injection line and mixed well in the buffer tank.This premixing in-line injection system has great potential to further reduce pesticide waste and improve environmental stewardship for conventional and precision variable-rate sprayers.Abstract To eliminate the problems associated with leftover tank mixture in pesticide applications, a premixing in-line injection system was designed as an attachment to a laser-guided variable-rate orchard sprayer. The primary components of the system consisted of a chemical metering pump, a water pump, a two-stage static mixer, a premixing tank, a buffer tank, an electric shut-off valve, a chemical container, electronic control boards, a graphical user interface, and an embedded computer with a touch screen. Liquid level sensors were mounted in all tanks and the chemical container to control the fluid discharge and prevent overflows. The graphical user interface on the touch screen was designed for operators to communicate with the system and monitor the system status. During spray applications, the system performed with automatic loops in dispensing, mixing, and transferring the desired amounts of water and chemical concentrates to maintain the spray mixture at a constant concentration for use with variable-rate nozzles. The system was rinsed automatically when the spray application task was completed. Test results showed that simulated pesticide and water could be accurately delivered into the injection line and could be mixed well in the buffer tank before the spray mixture was discharged to the nozzles. The premixing in-line injection system is a potential technique to further reduce pesticide waste and improve environmental stewardship for both conventional and precision variable-rate orchard sprayers. Keywords: Automation, Environmental protection, Intelligent sprayer, Pesticide spray application, Precision agriculture, Tank mixture leftover.

Design and performance evaluation of a variable-rate orchard sprayer based on a laser-scanning sensor

To improve the precision spraying strategy and reduce excessive pesticide application in orchards, an air-assisted sprayer integrated with a laser-scanning system was developed to realize the toward-target variable-rate spraying. In the spray control system, a method of calculating canopy gridding volumes was designed to ensure the canopy was divided into a uniform grid size, a variable-rate spray model was used in the flow rate decision software to control the spray output according to the canopy gridding volumes and travel speed, and a method of saving and accessing spray data was used to control the spray delay. The effects of different grid sizes and travel speeds on the spray performance were evaluated by quantifying spray coverage uniformity inside tree canopies. The results showed that spray coverage uniformity declined with increasing grid width from 0.14 to 0.28 m although the mean spray coverage on each target location showed no significant differences. Additionally, there were no significant variations in mean spray coverage at speeds of 1.0, 1.2 and 1.4 m/s for a tested tree of 1.6 m width and at any experimental speeds for a tested tree of 1.3 m width, which indicated that the variable-rate sprayer could provide good spray coverage uniformity under various travel speeds with a canopy size limitation. Compared with the same sprayer without the variable-rate spray function, the intelligent sprayer prototype realized effective toward-target spraying and avoided overspraying while providing sufficient spray coverage. Keywords: laser-scanning sensor, variable-rate spray, orchard, precision sprayer, pesticide application efficiency DOI: 10.25165/j.ijabe.20191206.4174 Citation: Cai J C, Wang X, Gao Y Y, Yang S, Zhao C J. Design and performance evaluation of a variable-rate orchard sprayer based on a laser-scanning sensor. Int J Agric & Biol Eng, 2019; 12(6): 51–57.

Control of Insects and Diseases with Intelligent Variable-rate Sprayers in Ornamental Nurseries

Abstract Intelligent spray technology can reduce pesticide use and safeguard the environment; however, its ability to effectively control insects and disease must be validated before its adoption by growers. Comparative tests for two different laser-guided variable-rate intelligent sprayers and the same sprayers with conventional constant-rate mode were conducted to control pests at two ornamental nurseries in two growing seasons in Ohio. Crabapple [Malus ‘Sutyzam’ (Sugar Tyme®), M. sargentii], apple (Malus pumila), maple [Acer ×freemanii ‘Jeffersred' (Autumn Blaze®), A. rubrum ‘Franksred' (Red Sunset®) and A. rubrum], birch (Betula nigra and Betula populifolia ‘Whitespire'), London planetree (Platanus ×acerifolia ‘Bloodgood') and dogwood (Cornus florida) were used as the test plants. Intelligent spray technology reduced pesticide use by 56.1% and 51.8% on average at the two nurseries, respectively. Compared to conventional air-assisted sprayers, severity of scab on apple trees and powdery mildew in dogwood was reduced on intelligent spray-treated plants at one nursery, and there were equal or fewer leafhoppers in maple trees and aphids in birch trees when sprayed using intelligent spray technology at both nurseries. These results suggest that intelligent, variable-rate sprayers achieve equivalent or greater insect and disease control in ornamental tree nurseries compared to conventional, constant-rate sprayers. Index words: aphid, apple scab, environmental protection, leafhopper, precision spray, powdery mildew, sustainable. Species used in this study: apple (Malus pumila Mill), birches (Betula nigra L, Betula populifolia Marsh. ‘Whitespire'), crabapples [Malus ‘Sutyzam' (Sugar Tyme®), M. sargentii Rehder], dogwood (Cornus florida L.), maples [Acer ×freemanii E. Murray ‘Jeffersred' (Autumn Blaze®), A. rubrum L. ‘Franksred'(Red Sunset®) and A. rubrum L.], London planetree [Platanus ×acerifolia (Ait.) Willd. ‘Bloodgood'].

Improved premixing in-line injection system for variable-rate orchard sprayers with Arduino platform

To reduce the tank mixture leftover problem associated with variable-rate orchard sprayers, an experimental automatic premixing in-line injection system was developed with Arduino platform. This system primarily consisted of a precision fluid metering pump, a water pump, a static mixer, a premixing tank and a buffer tank. The required amounts of water and chemical concentrates were accurately pumped into the premixing tank through a static mixer. The mixture was then transferred into a buffer tank for additional mixing process and for the spray pump to discharge to variable flow-rate nozzles. When the buffer tank neared empty, this process was repeated automatically to maintain the same chemical ratio for all nozzles regardless of their spray output differences and variations. Accuracy of the metering pump was verified with simulated pesticide concentrates (tap water, turpentine oil, prime oil, and four different viscous sucrose solutions) at viscosities between 0.9 and 32.0 mPa·s. With addition of a fluorescent tracer, the sucrose solutions were also used to evaluate the uniformity of spray mixtures discharged from the premixing in-line injection system. Test results demonstrated that the fluid metering pump could accurately dispense desired volume (10–300 mL) of simulated pesticides at different pump rotational speeds with relative errors between measured and desired volumes below 5%. The uniformity of spray mixtures at different chemical-to-water ratios (0.1%–2.0%) was consistent, and the highest relative error and coefficient of variation were 7.6% and 4.5%, respectively. The experimental premixing in-line injection system was proven to have stable and accurate performance, and thus would have great potentials to improve spray application efficiency with minimized tank mixture leftovers for future variable-rate sprayers.

Design of Plant Protection UAV Variable Spray System Based on Neural Networks.

Recently, unmanned aerial vehicles (UAVs) have rapidly emerged as a new technology in the fields of plant protection and pest control in China. Based on existing variable spray research, a plant protection UAV variable spray system integrating neural network based decision making is designed. Using the existing data on plant protection UAV operations, combined with artificial neural network (ANN) technology, an error back propagation (BP) neural network model between the factors affecting droplet deposition is trained. The factors affecting droplet deposition include ambient temperature, ambient humidity, wind speed, flight speed, flight altitude, propeller pitch, nozzles pitch and prescription value. Subsequently, the BP neural network model is combined with variable rate spray control for plant protection UAVs, and real-time information is collected by multi-sensor. The deposition rate is determined by the neural network model, and the flow rate of the spray system is regulated according to the predicted deposition amount. The amount of droplet deposition can meet the prescription requirement. The results show that the training variance of the ANN is 0.003, and thus, the model is stable and reliable. The outdoor tests show that the error between the predicted droplet deposition and actual droplet deposition is less than 20%. The ratio of droplet deposition to prescription value in each unit is approximately equal, and a variable spray operation under different conditions is realized.

Design and performance evaluation of a variable-rate orchard sprayer based on a laser-scanning sensor

To improve the precision spraying strategy and reduce excessive pesticide application in orchards, an air-assisted sprayer integrated with a laser-scanning system was developed to realize the toward-target variable-rate spraying. In the spray control system, a method of calculating canopy gridding volumes was designed to ensure the canopy was divided into a uniform grid size, a variable-rate spray model was used in the flow rate decision software to control the spray output according to the canopy gridding volumes and travel speed, and a method of saving and accessing spray data was used to control the spray delay. The effects of different grid sizes and travel speeds on the spray performance were evaluated by quantifying spray coverage uniformity inside tree canopies. The results showed that spray coverage uniformity declined with increasing grid width from 0.14 to 0.28 m although the mean spray coverage on each target location showed no significant differences. Additionally, there were no significant variations in mean spray coverage at speeds of 1.0, 1.2 and 1.4 m/s for a tested tree of 1.6 m width and at any experimental speeds for a tested tree of 1.3 m width, which indicated that the variable-rate sprayer could provide good spray coverage uniformity under various travel speeds with a canopy size limitation. Compared with the same sprayer without the variable-rate spray function, the intelligent sprayer prototype realized effective toward-target spraying and avoided overspraying while providing sufficient spray coverage. Keywords: laser-scanning sensor, variable-rate spray, orchard, precision sprayer, pesticide application efficiency DOI: 10.25165/j.ijabe.20191206.4174 Citation: Cai J C, Wang X, Gao Y Y, Yang S, Zhao C J. Design and performance evaluation of a variable-rate orchard sprayer based on a laser-scanning sensor. Int J Agric & Biol Eng, 2019; 12(6): 51–57.