Location: Application Technology Research
2024 Annual Report
Objectives
The long-term objective of this research is to advance spray applications with coordinated intelligent-decision technologies and strategies that enhance pesticide application efficiency and environmental stewardship for efficacious and affordable control of pest insects, diseases and weeds.
Objective 1: Develop intelligent precision technologies to efficiently apply pesticides and bio-products for efficacious and sustainable control of pest insects and arthropods, diseases and weeds to protect horticultural, field and greenhouse crops.
Sub-objective 1.1: Develop a reliable and user-friendly intelligent spray-decision system as a retrofit for new and existing air-assisted sprayers to deliver pesticides and bio-products accurately, economically, and environmentally for field specialty crops.
Sub-objective 1.2: Develop greenhouse intelligent spray systems for real-time control of individual nozzle outputs to improve spray deposition quality and reduce waste of water and chemicals.
Objective 2: Develop coordinated application methodologies to reduce pesticide use, reduce crop protection costs, reduce chemical contaminations to the environment, and protect workers, livestock, natural resources and sensitive ecosystems.
Sub-objective 2.1: Improve spray droplet fading process to maximize coverage area after deposition on plants through coordinating spray parameters including droplet size, formulation physical properties, plant surface morphology, and ambient air conditions.
Sub-objective 2.2: Improve spray droplet retention and reduce runoff on plants through coordinating the influences of droplet size and velocity, travel speed, spray formulation physical properties, crop leaf surface morphology, and leaf surface orientation on dynamic impact, retention, rebound and spread process of spray droplets on plants.
Approach
A versatile intelligent spray control system and mounting kits will be developed as a retrofit to different types of tractor-driven sprayers to deliver pesticides and bio-products for different specialty crops. A microprocessor controlled premixing inline injection module will be developed and integrated into the versatile spray control system. Performance of these sprayers will be tested for their accuracy to manipulate spray deposition, spray drift, off-target loss and spray volume consumption in comparison with conventional sprayers. Efficacy tests will be conducted in nurseries, apple orchards and vineyards to compare pest control, pesticide quantity used, and cost savings for the sprayers with and without intelligent functions. Spray drift models will be developed to predict movement of droplets discharged from conventional and intelligent sprayers under nursery, orchard and vineyard conditions.
Greenhouse intelligent spray systems will be developed for real-time control of individual nozzle outputs to improve spray deposition quality and reduce waste of water and chemicals. The automatic greenhouse spray system will be a retrofit attached to existing watering booms. Laboratory tests will be conducted to validate the spray control system accuracies in spray delay time, nozzle activation and spray volume using artificial objects of different regular geometric shapes and surface textures, and artificial plants of different canopy structures. Spray deposition and pest control efficacy tests in greenhouses will then be conducted to validate the intelligent spray control system.
Microscopic spray droplet spreading times and areas on leaves will be investigated to maximize and stabilize coverage area after deposition on plants. Investigation parameters include droplet size, formulation physical properties, plant surface morphology, and ambient air conditions. Droplet fading rate, absorption rate and residual pattern coverage area will be measured on the waxy, semi-waxy and hairy leaf surfaces, and hydrophilic and hydrophobic glass slide surfaces. Field experiments will be conducted in ornamental nurseries, orchards, greenhouses, vegetables, traditional crops and weeds to verify laboratory discoveries effects of the most influenced factors on droplet spreading areas.
Dynamic effects of spray parameters on the droplet impact, rebound, retention, adhesion, and spread process on plants will be determined. The parameters are droplet size and velocity, travel speed, spray formulation type, and leaf surface morphology and orientation.
Significance of coordinating these parameters to improve spray droplet retention and reduce runoff on plants will be analyzed. Dynamic impact of water-based droplets on plant leaves will also be investigated in a wind tunnel under controlled conditions.
Progress Report
In support of Objective 1:
Capability of 12 pulse width modulation (PWM) valves was investigated to control hollow-cone nozzles for variable-rate applications. Tests included PWM frequencies of 5 to 50 Hz and duty cycles (DUC) of 10% to 100%. The PWM valves were assembled on a laboratory spray system with a disc-core hollow-cone nozzle operated at 1380 kPa pressure. The upstream and downstream pressures on the PWM valves were recorded and analyzed to determine the maximum functional duty cycle ranges and maximum PWM frequency at which the PWM valves could manipulate the nozzle properly. Test results showed that there were noticeable differences in the modulation capability among the 12 PWM valves due to their design differences. Two out of 12 valves achieved the greatest functional DUC ranges at 40 Hz PWM frequency to manipulate open-close pulse actions of the hollow-cone nozzle. The two valves were continuously investigated on their flow rate modulation accuracy and pressure stability for hollow-cone nozzles. Flow rates, activation times, activation pressures, and the droplet size distributions were optimized. Flow rates of nozzles modulated with both valves increased linearly as DUC increased. In general, both PWM valves had comparable accuracy to modulate flow rates of the two hollow- cone nozzles with consistent droplet size distributions. The two valves could potentially increase the modulation accuracy by four times compared with the commonly used 10 Hz frequency valves, and they will be recommended for future integration into variable-rate spray systems to further increase application accuracy.
An experimental variable rate sprayer equipped with a low-cost stereo vision system was developed to minimize pesticide use for tree crops. The stereo vision detected the canopy and controlled sprayer output to apply pesticides to trees only in real time. The sprayer acquired digital images from the stereo vision system five times per second and processed them to modulate sprays ten times to tree canopies per second. The sprayer was evaluated in an apple orchard and was compared with a conventional sprayer under a range of typical travel speeds (3.2 to 8.0 km/h). Test results showed the sprayer only used spray volumes from 19.5% to 26.7% of the volume applied by the conventional sprayer. The conventional sprayer generally achieved higher spray deposition and coverage in tree canopies although the variable rate sprayer delivered significantly more uniform spray deposition (p=0.05) regardless of the sizes of apple trees. The sprayer with the stereo vision system may offer a cost-effective real- time variable rate spray option for growers. However, further experiments to evaluate the sprayer under various crop and field conditions must be carried out.
An electric air assist system (EAAS) was developed to control airflows based on plant foliage densities. The system consisted of an electric fan, a PWM controller, custom designed air channel and a 400-Ah LiFePO4 battery to electronically control intensity of air assist. Test results indicated the system required approximately 4 s to reach the maximum airflow although it took approximately 2.5 s to attain 80% airflow. Under the lab condition with 100% DUC of PWM, the EAAS could deliver airflows with velocities of 11.3 and 5.3 m/s at its outlet and 1 m away, respectively. It was also able to modulate air velocities from 0 to 11.3 m/s by simply changing a length of DUC signals in PWM modulation. Field tests throughout a growing season in an apple orchard showed no more than the airflow generated from the EAAS at 50% DUC would be necessary to minimize spray drift. In addition, a multivariable regression model was developed to predict desired airflow to minimize the off-target spray drift for given canopy densities.
In collaboration with horticulturists at University of Tennessee, an air-blast sprayer retrofitted with the laser-guided intelligent spray system was tested to directly compare spray characteristics and pest control between the variable-rate and constant-rate modes in a commercial nursery. Sprayed trees were grown in 57 L containers in a multi-row pot-in-pot production system. Variable-rate mode reduced total spray volume by 43% while providing equivalent, and at times better, disease control than the constant-rate mode for two fungal borne diseases of Shumard oak. This research demonstrated the capability of variable-rate technology to reduce input costs, environmental harm, and pesticide exposure risks while simultaneously controlling disease and maintaining saleable crops.
In collaboration with plant pathologists at The Ohio State University, a laser-guided intelligent sprayer was evaluated in an experimental vineyard. Treatments included the intelligent sprayer with low and high base spray deposition rates, and the conventional constant-rate application using the same sprayer but with the intelligent functions deactivated. Evaluations included comparisons of spray coverage and deposition uniformity within vines, spray volume consumption, chemical cost savings, control of fungal diseases and Japanese beetles, and yields among the three treatments and nontreated plots as control. With comparable insect and disease controls, the intelligent spray treatments reduced spray volume by 29% to 83% compared to the conventional spray treatment, resulting in annual chemical savings of $469 (high rate) and $712 (low rate) per hectare.
In support of Objective 2:
An open circuit low-speed wind tunnel was developed and constructed for pesticide spray application technology investigations. Primary components of the wind tunnel were a centrifugal fan, a fan housing assembly with a variable speed motor, a permeable airflow deflector, a wide-angle diffuser, a contraction chamber, a honeycomb settling chamber and a detachable test section. The total length of the wind tunnel was 16 m including the 7 m test section with finished smooth ground surface. The cross-section area of the test section was 1.83 x 1.83 m. The wind tunnel was designed by following standard instructions and computational fluid dynamics models to produce airflows up to 12 m/s. To evaluate uniformity of wind speeds at different target speeds, air speeds were measured with a hot-film anemometer at 16 points evenly distributed across each of four cross sections in the test section. Coefficients of variation for the air speeds across the entire cross sections were below 5% for all target speeds.
Effects of wind speed, nozzle type, and plant density on spray coverage inside the soybean canopy were determined in the open-circuit wind tunnel. Tests included four wind speeds, four types of nozzles to produce medium to very coarse droplets, and two soybean planting densities). A stationary spray boom with three identical nozzles was installed inside the wind tunnel at 0.5 m above the canopy. Soybeans were placed on the floor of the wind tunnel, starting 0.5 m upwind up to 3 m downwind the spray boom. To determine the spray coverage, water sensitive papers were placed and analyzed at three different heights (top, middle and bottom) inside soybean plants located downwind from the spray boom. Air speeds were measured with a 3D hot-wire anemometry system at four vertical positions: above the canopy, and at top, middle and bottom of the canopy. For all nozzles, the top of the canopy always received the greatest amount of spray coverage followed by the middle position. Regardless of the nozzle type, significantly lower amount of spray deposition was found at the bottom part of the canopy in all the sample collection locations. The results also showed that the plant density significantly influenced the air movement inside the soybean canopy.
Accomplishments
1. Low-cost stereo vision system for variable-rate sprayers. Pesticide applications with conventional sprayers generally achieve sufficient protection of crops, but their efficiency is very low due to huge pesticide waste to non-target areas. In previous work, ARS engineers at Wooster, Ohio, developed an advanced variable rate spraying system guided with a laser sensor as a retrofit for the sprayers to reduce pesticide use while preserving the efficacy. The spraying system was commercialized and rapidly adopted by specialty crop growers. While the laser sensor is a very accurate detection device, it is also very expensive for small to medium sized farms to afford the system. Thus, ARS engineers at Wooster, Ohio, have investigated a low-cost stereo vision system (approximately 10% of the laser sensor) as an alternative to the laser sensor. A new algorithm was developed for the stereo vision system that could detect a 2.5-cm wide target over 1.5 m away from the system. Laboratory and field tests demonstrated that the stereo vision system will be a more affordable device with adequate accuracy to detect tree crops for variable rate spray applications. Thus, it could be used in a new variable rate spraying system for small to medium sized farms.
2. New electric variable air assist system for specialty crop sprayers to ensure penetration of spray into the canopy. Pesticide applications for specialty crops often utilize air assistance to increase spray penetration into canopies. Typically, specialty crop sprayers are equipped with a large axial fan to generate a large amount of airflow that carries spray droplets to targets; however, excessive airflow often pushes spray droplets beyond the targets, causing too much spray drift and potentially wasting spray. ARS engineers at Wooster, Ohio, developed an electric variable air assist system to adjust the amount of airflow based on canopy density for different crop sizes and growth stages to minimize off-target spray loss. The new variable air assist system is anticipated to be an effective alternative to conventional air assist systems for specialty crop growers to significantly increase application efficiency for crop protection and greatly reduce spray drift to the environment.
3. New high-speed high-pressure valves to improve application accuracy of precision sprayers. Pulse width modulation (PWM) solenoid valves are a critical component for sensor-guided precision sprayers to achieve variable-rate applications. The valve changes spray nozzle outputs every tenth of a second based on the plant structure data collected by the plant detection sensor. However, activation speeds of current PWM valves are four times slower than the detection sensor speed, so the slow speed of PWM valves restricts the efficient use of the high-speed sensors to achieve the maximal variable-rate application accuracy. ARS engineers at Wooster, Ohio extensively investigated 12 different valves originally designed for industrial applications, and discovered two of them were able to match the sensor speeds to modulate flow rates of high-pressure nozzles in time. The valves were capable of improving spray application accuracy by up to 400%. Thus, these valves could be integrated into future designs of new precision sprayers by engineers for specialty crop growers to further maximize pesticide application efficiency and minimize pesticide loss to the environment.
Review Publications
Fessler, L., Xiaocun, S., Wright, W.C., Zhu, H., Fulcher, A. 2023. Intelligent, variable-rate spray technology reduces total pesticide output while controlling foliar disease of Shumard oak. Journal of Environmental Horticulture. 41(3):109-120. https://doi.org/10.24266/0738-2898-41.3.109.
Womac, A., Ozkan, E., Zhu, H., Kochendorfer, J., Jeon, H., Eswarachandra, N. 2023. Wind tunnels and their uses to study variables affecting precision applications of agricultural sprays. Journal of the ASABE. 66(5):1135-1151. https://doi.org/10.13031/ja.15622.
Roman, C., Jeon, H., Zhu, H., Ozkan, E., Campos, J. 2023. Stereo vision controlled variable rate sprayer for specialty crops: Part III. Effect of travel speeds on spray deposition and ground loss. Journal of the ASABE. 66(6):1469-1479. https://doi.org/10.13031/ja.15699.
Shannon, B., Jeon, H., Johnson, R. 2023. Review: The risks of spray adjuvants to honey bees. Journal of Insect Science. 23(6). Article 20. https://doi.org/10.1093/jisesa/iead100.
Roman, C., Jeon, H., Zhu, H., Campos, J., Ozkan, E. 2023. Stereo vision controlled variable rate sprayer for specialty crops: Part II. Sprayer development and performance evaluation. Journal of the ASABE. 66(5): 1005-1017. https://doi.org/10.13031/ja.15578.
Xun, L., Campos, J., Salas, B., Fabregas, F.X., Zhu, H., Gil, E. 2023. Advanced spraying systems to improve pesticide saving and reduce spray drift for apple orchards. Precision Agriculture. 24:1526-1546. https://doi.org/10.1007/s11119-023-10007-x.
Wodzicki, L.M., Madden, L.V., Long, E.Y., Zhu, H., Ivey, M.L. 2023. Evaluation of a laser-guided intelligent sprayer for disease and insect management on grapes. American Journal of Enology and Viticulture. 74. Article 0740024. https://doi.org/10.5344/ajev.2023.23013.
Fulcher, A., Rihn, A., Warner, L., LeBude, A., Schexnayder, S., Altland, J.E., Baumgarner, N., Marble, C., Nackley, L., Palma, M., Velandia, M., Zhu, H., Gan, H., Owen Jr, J.S. 2023. Overcoming the nursery industry labor shortage: a survey of strategies to adapt to a reduced workforce and automation and mechanization technology adoption levels. HortScience. 58(12): 1513-1525. https://doi.org/10.21273/HORTSCI17230-23.
Campos, J., Zhu, H., Jeon, H., Salcedo, R., Ozkan, E., Roman, C., Gil, E. 2023. Air-pinch PWM valve to regulate flow rate of hollow-cone nozzles for variable-rate sprayers. Journal of the ASABE. 66(5): 1317–1329. https://doi.org/10.13031/ja.15601.
