AUTONOMOUS ROBOTIC SCOUT AND PRECISION SPRAYER FOR HIGH DENSITY CITRUS

Since the advent of HLB in Florida, the profitability and viability of citrus production has been gradually diminishing due to declining crop yield and quality, and significant increase in production costs due to Asian Citrus Psyllid (ACP, Diaphorina citri) control and Foliar Nutritional Application (FNA) that attempt to compensate for loss of nutritional uptake through damaged root systems. The intensive use of canopy applied psyllid control and foliar nutritional programs demonstrate the need for highly accurate spray delivery systems that only spray tree canopy, and vary application according to within grove variability. These same conditions apply to disease control measures for postbloom fruit drop (PFD) and citrus black spot (CBS). A recent economic analysis by Singerman showed that the annual cultural costs for SW Florida juice orange was $1910/ac/yr, with the cost for spray applications at $630/ac/yr, or 33% of the production costs.Long term hope rests on finding HLB resistant varieties and developing management strategies that can control the psyllid population and manage trees in an optimal economic framework. One management approach being considered is Advanced Citrus Production Systems (ACPS) that use high-density (HD) semi-dwarfed trees and open hydroponics with optimized nutrient and water availability, which accelerates plant growth. Another approach being considered is Citrus Under Protective Screen (CUPS), CUPS uses HD semi-dwarfed trees or potted trees to limit tree size due to canopy height limitations. Citrus production under enclosed structures can exclude the ACP and eliminate the negative effects of HLB caused byCandidatusLiberibacter asiaticus to the grapefruit (Citrus paradisi) fresh fruit industry. Since the discovery of the ACP, the importance of developing advanced production systems has only increased. This is evidenced by the growing number of aces being planted in CUPS. At the end of 2019, Ferrarezi reported that there were in excess of 400 acres of CUPS in Florida, while recent conversations with Dundee Growers report that they alone plan to establish over 1000 acres in CUPS at approximately $40K/acre establishment cost for structure, trees, irrigation, and other infrastructure. Thus, demonstrating the confidence and commitment that some growers have towards CUPS.Both of these production approaches, will require new equipment systems to manage production and harvesting. Autonomous operations and equipment are well suited for both ACPS and CUPS, which both require closely spaced smallish plants. Such trees have known efficiencies in their cultural and harvesting management, and constitute ideal orchard systems to accommodate autonomous scouting, pruning, mowing, spraying, and harvesting. Likewise, many of the same sensor, control and automation/robotic features will be relevant for both applications with the primary difference being the mobile platform design used for CUPS vs. ACPS. CUPS will likely be applied to high value crops (e.g., grapefruit) that can offset the high startup costs. At a smaller production scale with high value fruit, trees can be managed in an optimal fashion for improving spraying and harvesting effectiveness due to reduced tree height and shallow canopy depths grown in a fruiting wall. In addition, the screen provides a natural solar light diffuser for illumination optimization that will assist in optimizing disease and pest scouting as well as robotic harvesting. The shallow canopy depth will improve spray penetration and minimize harvesting obstacles.In this Phase I proposal, we will focus on the building a proof of concept prototype CUPS scout and precision sprayer at an approximate ¼ scale. The eventual Phase II system will consist of three primary sub-systems. First, the Autonomous Scout Powerplant which will be powered by a 50 HP diesel engine with both hydraulic and electric power distribution via a generator and hydraulic pumps. The scout will be capable of running independent of implements during scouting missions being equipped with a suite of situation awareness sensor technologies, which can monitor spatial position within CUPS, map tree canopy profile and volume, guide the vehicle with obstacle avoidance, conduct disease and pest surveillance to assist precision sprayer and map fruit positions to assist selective harvesting. The second primary sub-system is the trailer mounted precision sprayer, which will be powered and controlled by the scout powerplant. It will be equipped with a water supply tank, chemical storage canisters, chemical injectors for custom blending and individual sprayer solenoids for precise application coverage. The initial sprayer, which we will evaluate, will use air-assisted low-volume atomizing technology to penetrate canopy with precision nozzle control. The sprayer will be controlled based on real-time scouting information and prescription maps according to disease/pest pressure provided by the RSPS scout or human experts, and other horticultural factors that may impact spray treatment efficacy. The third subsystem will be the subject of future research for development of the CUPS-based selective harvesting platform, which like the precision sprayer will be powered and controlled by the scout. These three technologies will also be directly applicable for the ACPS sprayer and harvester.The specific objectives of this proposal are as follows: 1) Evaluate current designs, 2) Design and modify RSPS, 3) Integrate sensors and software in sprayer rig, 4) Modify MSPS JD Gator with sensor suit and software, 5) Adapt/retrofit precision sprayer rig on MSPS, 6) Integrate MSPS sensors and software with precision sprayer, 7) Conduct proof of concept trials, 8) Refine Commercialization Plan and Report.