We aimed to improve accuracy of spray placement and dosing in dynamic vineyard environments. Our LiDAR and RADAR-based systems for assessing canopies before and during spraying were evaluated throughout the season, using variable rate Pulsed Width Modulation. Our novel electronic leaves with transmitters verified and audited deposition. Using a recycle sprayer or our ducted sprayer with LiDAR, we reduced chemical use rates for the same spray coverage throughout the season. Savings were 50-90% in sparse canopies with large gaps through to 10-50% for dense canopies without gaps. A commercial retrofit sensor system will be available in Australia in late 2020.
This is a project involving novel sensors to improve dosing of chemical sprays applied to vine crops according to each unique canopy, as part of a larger Digital Viticulture project.
Research was conducted in wind tunnel and field trials to develop and evaluate systems for optimisation of spraying in vineyards according to the dynamic canopy environment. Precision, variable rate and targeted spraying require accurate assessment of the canopy which changes throughout the season and within and between each vine plant and row. To assess these site-specific characteristics, assessments can be made visually or using digital tools such as sensors. The purpose of this project was to develop and assess various systems which can be applied as modifications to existing spraying systems or through investment in a specialised sprayer when new equipment is purchased. Our research considered existing Apps such as VitiCanopy, PIX4D imaging, PARbar ceptometers and other existing LAI measurement systems well as prototype new systems to automate spraying with LiDAR sensors for canopy characterisation in real-time, linked with RADAR for speed measurement to offset the timing of activation of solenoids to deliver variable spray rates through each nozzle according to both the target surfaces (leaves and woody vine materials) and local canopy density which usually progressively increases from winter to spring to summer. An alternative dose and drift management support approach was also tested in the form of recapture/ recycle spraying, which unlike the LiDAR application management approach was commercially available at the start of the project.
We developed and tested electronic leaf spray coverage systems with an aim to replace water sensitive papers and fluorescent dyes with digital sensors for spray coverage and auditing. We explored the use of unmanned application systems as robotic platforms for future spraying.
Our research showed that manual assessments of spray canopy structure and target locations can be replaced or supplemented with automated systems to control the spray placement and dose rate in real time, offering equal spray coverage with reduced spray volumes. Such systems could be added to modify existing sprayers or by late 2020, available as a commercial system with some changes from our test system such as a different LiDAR system, the use of GPS rather than RADAR and improved solenoid systems for higher spray pressure use. We found that recapture/ recycle sprayers could also offer similar results of improved spray placement and dosing without spray losses through drift and runoff, for cases where end-users would decide to invest in a new sprayer. In our tests, LiDAR-supported and recapture/ recycle spraying systems offered greater savings in chemical use and drift reduction with lower canopy density – in other words, the greatest benefits occurred earlier in the spray season with savings in chemical up to 70-90%, but with high savings (up to 30%) even at late growth stages when canopies are fully developed with fruit. For specific targets such as spraying only the woody materials for dieback disease management, chemical savings exceed 90% and targeting is precise, allowing 100% coverage automatically without human control with the use of appropriate nozzles/ pressures.
Drift reductions from LiDAR sensor spraying and recycle spraying closely matched the reductions in chemical use rates with 60% being typical.
Our research showed that pulsed width modulation (PWM) offers an effective way of delivering the optimal spray dose rate for each local canopy density. However, we established that unlike prior broadacre crop application work with flat fan nozzles and ground horizontal boom sprayers, the cone types of nozzles and higher pressures commonly used in viticulture do not always offer constant droplet size across the operating PWM duty cycle rates, so care must be taken to select nozzles that are compatible with spray angle and droplet size requirements.
Robotic platforms can perform well, especially if spray placement is adjusted with changing weather conditions such as through swath displacement when using drones. In order to achieve sufficient canopy penetration with a drone sprayer, small droplets should be applied, but care must be taken to offset the aircraft position and avoid the spray missing the rows. Indeed, wind displacement of spray is an issue for LiDAR sensor sprayer applications as well, when canopy density is sparse. Our research suggests drones and for sparse canopies (early season) ground LiDAR-equipped targeted sprayers should only be used when the wind speed is below 10 km/h. On the other hand, recapture/ recycle sprayers increase the weather window for spraying all canopy densities to double this speed and in some cases even higher.
Electronic leaves are effective for assessing spray deposition and transmitting data back to the spray control system for auditing and verification of coverage.
We are acquiring a commercial system in the near future to evaluate as a final step for offering growers off-the-shelf LiDAR control systems later in 2020. It, along with a novel ground robotic platform, has been delayed in 2020 with the unexpected COVID-19 situation.
We would like to acknowledge the support from other groups which enhanced the findings of this project, such as the provision of dedicated project sprayer (Oktopus) and staff support from Silvan, the provision of sprayers and staff for field tests from FMR, access to vineyards, staff support and equipment use such as tractors and sprayers in several states including Vinland Estates (QLD), Ballandean (QLD/ NSW), Sergi Fresh (VIC), TWE Cullulleraine (VIC) and planned tests in late 2020 of commercial systems in Langhorne Creek (SA). We appreciate the support of our colleagues for LiDAR control system work from USDA and comparison with European dosing approaches and field tests in Australia from Lleida University, Spain, dosing approaches in Australia, Geoff Furness and in the UK, Peter Walklate. We also wish to thank our colleagues from other organisations who assisted with equipment and/ or field test manpower such as NERCITA, Revolution Ag, Spectrum Electrostatics and Spraying Systems/ Teejet.
Our research revealed some interesting findings which were not previously known and which could benefit from additional future research such as the need to select appropriate nozzles for use with pulsed width modulation, given that new nozzle designs such as air induction and modified cones are often different from prior types and may offer unexpected spray angles and droplet sizes for different pulse rates. Our work on electronic leaves should be further developed for integration within spray decision and accounting support systems, having shown proof of concept in this research. The use of robotic platforms and in particular aerial drones for spraying requires future research for optimisation across different vineyard types and pest control/ spray application needs. Future research is also suggested to look at alternative systems for individual nozzle variable rate spray release such as low-cost sensors and solenoids on each nozzle. We also believe that the whole area of digital spray targeting and traceability requires ongoing research as new sensors and changing regulatory and consumer demands concerning pesticide use evolve.
This project was supported by Wine Australia, through funding from the Australian Government Department of Agriculture, Water and the Environment as part of its Rural R&D for Profit program, Horticulture Innovation Australia Limited and the University of Queensland.