Improve Spray Deposition Research Articles

Adjusting Air-Assistance and Nozzle Style for Optimized Airblast Sprayer Use in Eastern Washington Vineyards

<h3>Summary</h3> <h3>Goals:</h3> There are many ways to optimize an airblast sprayer for use in vineyards. Three techniques growers use include: 1) changing nozzle type, 2) reconfiguring or adjusting the nozzles, and 3) adjusting the air-assistance to the droplets during an application. This study evaluated the effects of nozzle type and air-assistance use in airblast sprayers on canopy spray deposition and drift in a Washington wine grape vineyard that is trained to a modified vertical shoot positioning system. <h3>Key Findings:</h3> The one-piece nozzle with air assistance showed consistently high total collected canopy deposition regardless of time of season (early or mid-season). However, drift was reduced when air-assistance was not used. The air induction nozzle had the greatest total collected canopy deposition when using air-assistance during the early season, but had the greatest deposition mid-season without using air-assistance. Drift was reduced when air assistance was not used. Early in the growing season, maximum spray deposition in the fruiting zone of the canopy was achieved using air induction nozzles with air-assistance. However, if one adopted the use of air induction nozzle, <i>without air</i>, that would optimize fruiting zone spray deposition, while reducing captured aerial drift. Mid-growing season, maximum fruiting zone spray deposition without high drift was achieved using air induction nozzles without air-assistance. <h3>Impact and Significance:</h3> An airblast sprayer optimized through changes in nozzle or use of air-assistance can improve spray deposition into the canopy while minimizing drift. Growers can compare and adopt these drift-reduction techniques, i.e., using air induction nozzles and / or turning air-assistance off, to determine which are best suited for their farming practices. Such approach will allow better optimization of the sprayer for their vineyard spray application needs as well as reduce the possible negative impacts associated with off-target chemical deposition on humans and the environment.

Influence of nozzle enabling strategy on spray deposition of crop protection unmanned aerial system

Proper nozzles arrangement is significant to improve spray deposition of crop protection unmanned aerial system (UAS). Besides fuselage structure, the control strategy is another nozzle location changing method when there are multiple sets of nozzles. A four-rotor crop protection UAS equipped with four centrifugal nozzles was used to conduct a field experiment in the rupturing stage of rice. Two sets of nozzles in the front and rear of the fuselage were enabled independently to investigate spray deposition, including spray coverage and droplet density on the sampling cards. Various nozzle rotating speeds and flight speeds were employed in the experiment to study the influence of nozzle location on the deposition. With different nozzle rotating speeds, the droplet spectrum could be controlled. The results show that the average coverage and average cumulative droplet density are negatively correlated with flight speed. Average droplet density is also negatively correlated with the droplet size. Spray deposition of front nozzles is significantly reduced compared with that of the rear nozzles under the same spray parameters, especially when the droplet size is too large or the flight speed is too fast. The reduction is mainly concentrated in the center area of the spray swath. As a result, the average cumulative droplet density of the front nozzles decreases by 25.96% in total. The average droplet density decreases by 18.54% when the droplet size is smaller than 100 μm, decreases by 25.02% when between 100 μm and 200 μm, and decreases by more than half when larger than 200 μm. This research can provide guidance for the installation of UAS nozzles and spray control strategy design. Keywords: crop protection, unmanned aircraft system, nozzles arrangement, spray coverage, droplet density DOI: 10.25165/j.ijabe.20211403.5922 Citation: Gu W, Xue X Y, Chen C, Zhou Q Q, Zhang S C, Peng B. Influence of nozzle enabling strategy on spray deposition of crop protection unmanned aerial system. Int J Agric & Biol Eng, 2021; 14(3): 53–61.

Controlling droplet deposition with surfactants

Surfactants are often added to sprays to improve spray deposition. We show how the dynamic surface tension of surfactants solutions can be evaluated from drop impact experiments, allowing for a better understanding of drop deposition in the presence of surfactants.

Spray Deposition on Weeds (Palmer Amaranth and Morningglory) from a Remotely Piloted Aerial Application System and Backpack Sprayer

This study was designed to determine whether a remotely piloted aerial application system (RPAAS) could be used in lieu of a backpack sprayer for post-emergence herbicide application. Consequent to this objective, a spray mixture of tap water and fluorescent dye was applied on Palmer amaranth and ivyleaf morningglory using an RPAAS at 18.7 and 37.4 L·ha−1 and a CO2-pressurized backpack sprayer at a 140 L·ha−1 spray application rate. Spray efficiency (the proportion of applied spray collected on an artificial sampler) for the RPAAS treatments was comparable to that for the backpack sprayer. Fluorescent spray droplet density was significantly higher on the adaxial surface for the backpack sprayer treatment than that for the RPAAS platforms. The percent of spray droplets on the abaxial surface for the RPAAS aircraft at 37.4 L·ha−1 was 4-fold greater than that for the backpack sprayer at 140 L·ha−1. The increased spray deposition on the abaxial leaf surfaces was likely caused by rotor downwash and wind turbulence generated by the RPAAS which caused leaf fluttering. This improved spray deposition may help increase the efficacy of contact herbicides. Test results indicated that RPAASs may be used for herbicide application in lieu of conventional backpack sprayers.

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.

Impact and Adhesion of Surfactant-Amended Water Droplets on Leaf Surfaces Related to Roughness

Highlights The relationship between impacting droplet deposition and leaf surface roughness was examined. Complete deposition occurred on smooth leaves with roughness heights shorter than 1.5 micrometers. Droplet deposition on rough leaves was best achieved at low initial travel speeds and high surfactant concentrations. This research provides understanding of increasing droplet adhesion on plants for pesticide spray applications. Abstract. Understanding the effects of the microscopic-scale surface roughness of targeted leaves on spray droplet retention and spread can help develop optimal strategies to improve pesticide application efficiency. Improved spray deposition would minimize the amounts of chemicals to be applied and reduce off-target losses and production costs while protecting the environment. A 3D optical surface profiler was used to measure the arithmetic mean roughness height (Sa), providing a reliable metric for microscopic-scale leaf surface roughness. The relationship between leaf surface roughness and droplet deposition was examined by correlating droplet adhesion with the Sa of six leaf types for spray solutions at five surfactant concentrations (0.0% to 0.75%) and eight initial droplet horizontal travel speeds (0.5 to 4.5 m s-1). Leaf roughness and wettability, in terms of Sa and contact angle (θc), ranged from smooth and easy-to-wet to rough and difficult-to-wet (37° 1.6 μm), deposition decreased with increasing Sa and initial droplet horizontal flight velocity, while it increased as surfactant concentration increased. Thus, spray deposition on rough leaf surfaces could be greatly improved with slow initial droplet flight speeds and high surfactant concentrations. In contrast, greater deposition on smoother leaf surfaces could be achieved at any initial droplet flight velocity and with low concentrations of non-ionic surfactant, or possibly none.

Simulation and Validation of the Air Flow generated by a Multi-Channel Air-Assisted Sprayer

The multi-channel air-assisted spraying can distribute air flow according to the crown diameter and be helpful to improve spray deposition and in the reduction of environmental pollution. However, the factors of air flow distribution are not clear. Computational fluid dynamics (CFD) simulation was used in this paper to investigate the influence of the fan speed (600-1800 rpm) and the distance from the air outlet (0-6.0 m) on the airflow field distribution. The measurements and the simulation results were consistent within the boundary of the test range. The results indicated that the airflow field in the central plane was basically axis-symmetric. The airflow field diffused in the central plane at a certain angle of diffusion. The air velocity first increased and then gradually decreased along the central line, and it displayed an exponential function. Within the range of 1.0 m from the air outlet, there was an obvious section of static air between the adjacent air outlets. Beyond this range, the airflow was well-distributed, and the air velocity was normally distributed at the height y. The airfield generated by the multi-channel sprayer was elliptical in its cross-section from the outlet (for x > 1.0m). The distance of the air supply significantly influenced the fluctuation of the velocity of the airflow, while the speed of the fan had no significant influence on the position of the confluence point of the airflow and the fluctuation of the velocity of each test section.

Experimental and numerical analysis of the spray application on apple fruit in a bin for postharvest treatments

Postharvest treatment of fruit inside a cool room is gaining more interest to replace spray applications in the orchard. The efficacy of the application depends on the quality of the spray liquid and its distribution inside fruit bin. This work investigated the effect of different modes and settings of airflow delivery on the deposition amount and uniformity of the cold fogging spray deposition in a single bin. Room air circulation by means of evaporator fans was compared to an air suction configuration using a tunnel and suction fan. Deposition tests were conducted using a mineral chelate tracer solution and filter paper collectors placed on fruit. A computational fluid dynamics (CFD) model of the spraying process was developed to simulate the airflow, droplet particle tracks and spray deposits on fruits. The model predicted well the position of maximum and minimum deposit and the relative differences between the different modes and settings of airflow delivery. Generally, deposition distributions were strongly non-uniform. Spray deposits on fruit using only room air circulation were very low. Using suction airflow that directs the spray through the bin improved spray deposition and uniformity. The effects of spraying under different suction pressures (50, 167, 314 and 500 Pa) across the bin using different droplet diameters (15, 100, 200 and 300 μm) was evaluated. Depending on the size, different effects were observed. Coarse droplets perform best in terms of uniformity of deposition with more lateral dispersion, whereas fine droplets have a very limited lateral dispersion, travels deep to the stack following the high-velocity air (better axial dispersion). By implementing multiple nozzles the poor lateral dispersion of fine droplets can be improved, hence, the desirable characteristics of fine droplets in penetrating into the stack (axial distribution) can be retained.

Optimization of spray deposition and Tetranychus urticae control with air assisted and electrostatic sprayer

Improved spray deposition can be attained by electrostatically charging spray droplets, which increases the attraction of droplets to plants and decreases operator exposure to pesticide and losses to the environment. However, this technique alone is not sufficient to achieve desirable penetration of the spray solution into the crop canopy; thus, air assistance can be added to the electrostatic spraying to further improve spray deposition. This study was conducted to compare different spraying technologies on spray deposition and two-spotted spider mite control in cut chrysanthemum. Treatments included in the study were: conventional TJ 8003 double flat fan nozzles, conventional TXVK-3 hollow cone nozzles, semi-stationary motorized jet launched spray with electrostatic spray system (ESS) and air assistance (AA), and semi-stationary motorized jet launched spray with AA only (no ESS). To evaluate the effect of these spraying technologies on the control of two-spotted spider mite, a control treatment was included that did not receive an acaricide application. The AA spraying technology, with or without ESS, optimized spray deposition and provided satisfactory two-spotted spider mite control up to 4 days after application.

The use of adjuvants to improve spray deposition and Botrytis cinerea control on Chardonnay grapevine leaves

Spray adjuvants have the potential to improve deposition by effecting uniform distribution of the active ingredient on plant surfaces. In order to study whether such a qualitative improvement of spray deposition would lead to improved disease control, a laboratory experiment was conducted on artificially inoculated grapevine (cv. Chardonnay) leaves. Prior to inoculation with Botrytis cinerea conidia in a spore settling tower, leaves were sprayed to pre-runoff with 1 mL of a mixture of fenhexamid, a fluorescent pigment, and one of 15 selected commercial adjuvants to manipulate the deposition quality of a specific quantity of spray. Following an incubation period of 24 h at high relative humidity, leaf discs were plated onto Petri dishes with paraquat-amended water agar and rated for development of B. cinerea from isolated leaf discs 11 d later. Spray deposition on leaves was assessed with a spray assessment protocol using fluorometry, photomicrography and digital image analyses. B. cinerea incidences on the upper and lower surfaces of water-sprayed leaves averaged 90.4% and 95.8%, respectively. Despite full spray cover of leaves, applications with fenhexamid alone did not completely prevent infection and resulted in 34.6% and 40.8% B. cinerea incidences on the upper and lower surfaces of leaves, respectively. Through the addition of certain adjuvants, B. cinerea incidences were significantly reduced (incidences of 2.9–17.1% and 10.0–30.8%, respectively), while some adjuvants did not differ from the fungicide only treatment, even though they might have improved spray deposition. In a histopathology study using epifluorescence microscopy, distinct differences were observed in conidium mortality (20.5% vs. 31.2%), germination (60.4% vs. 51.4%) and germ tube lengths (27.8 μm vs. 19.7 μm) between Hydrosilicote and Solitaire in combination with fenhexamid, even though both adjuvants effected similar quantitative and qualitative spray deposition. The study clearly demonstrated the potential of adjuvants to improve the bio-efficacy of a fungicide directly through improved deposition on grapevine leaf surfaces, although bio-efficacy might be influenced by adjuvant mode of action in some cases.

Development of a Canopy Opener to Improve Spray Deposition and Coverage Inside Soybean Canopies: Part 1. Mathematical Models to Assist Opener Development

A mechanical device, the canopy opener, is being designed to bend tops of soybean plants, creating a pathway for sprayed pest control agents into the lower crop canopy. Mathematical models were developed to aid opener design and placement to maximize spray penetration and coverage with minimum crop damage. The models established relationships among plant deflection, opener depth inside the canopy, and plant height, enabling determination of opening width based on calculations of plant-recovery motion after release from the opener and time available for droplet travel from the nozzle to the lower canopy. To provide parameters to support the developed model, natural frequencies and damping coefficients of soybean plants were determined experimentally. Additionally, times required for droplet travel from specific nozzles to the lower canopy were determined using a laser velocimetry system. The models predicted that for XR8004 nozzles at 276 kPa the maximal opener depth would be 0.14 m and the opener width should range from 0.04 to 0.47 m for 1.06 m tall soybean plants. Experimental measurement of maximal deflection and plant motion agreed with mathematical models.

Development of a Canopy Opener to Improve Spray Deposition and Coverage Inside Soybean Canopies: Part 2: Opener Design with Field Experiments

Conventional boom sprayers usually are not effective in delivering droplets to inner parts of dense target canopies, such as soybeans at growth stages from R3 to R5. An experimental mechanical canopy opener was developed with the assistance of mathematical models and attached to a conventional boom sprayer to increase spray deposition and coverage inside soybean canopies. The opener consisted of a 2.5 cm diameter metal pipe to push canopies forward, and a frame for connecting the pipe to the spray boom. Field experiments were conducted to determine the amount of spray deposition and percentage of spray coverage on artificial targets at the middle and lower portions of soybean canopies with three opener depths (7.5, 15, and 22.5 cm), three opener widths (15, 25, and 35 cm), and two different sizes of flat-fan nozzles. Additional field experiments were conducted to compare spray deposition and coverage inside soybean canopies among treatments using an air-assisted sprayer, the conventional boom sprayer with the opener, and the boom sprayer with a conventional flat-fan nozzle and a dual-pattern nozzle assembly without the opener. At the time of experiments, the soybean plants were at R5 growth stage with an average height of 1.06 m. An opener width of 25 cm or larger significantly increased the spray deposition and coverage inside the canopies. An opener depth from 7.5 to 15 cm had better spray coverage than the 22.5 cm opener depth. The boom sprayer with the opener produced no significant difference in spray deposition and coverage at the middle of canopies compared to the air-assisted sprayer, but it did produce significantly lower spray deposition and coverage at the lower portions of canopies than the air-assisted sprayer. With assistance from the opener to push the top of canopies, spray deposition and coverage on targets inside soybean canopies by the boom sprayer was improved.

Effect of Pruning on Apple Scab in Organic Apple Production

In a 3-year Hungarian study, the effectiveness of apple tree pruning as a management tactic for control of apple scab (Venturia inaequalis) was investigated on two susceptible (cvs. Jonagold and Mutsu), two moderately susceptible (cvs. Elstar and Idared), and two Vf resistant apple cultivars (cvs. Liberty and Prima) in three high-density organic apple orchards treated with copperand sulfur-based fungicide programs. The area under the disease progress curve (AUDPC) for leaf and fruit incidences was calculated to evaluate three winter pruning treatments (unpruned, weakly pruned, and strongly pruned). Strong pruning significantly decreased leaf scab on the susceptible and the moderately susceptible cultivars at all sites compared with unpruned ones. Moreover, for the cultivar Jonagold in all years and for the cultivar Mutsu in 2001, AUDPC values of strongly pruned trees were significantly lower at P = 0.05 compared with the weaklypruned trees. The effect of pruning on development of fruit scab was weaker than on leaf scab in all years and at all sites. For fruit scab incidence on susceptible cultivars, only strong pruning treatments decreased AUDPC significantly compared with unpruned treatments. The effects of pruning treatments on moderately susceptible cultivars were significant only in 2001 at all sites. Resistant cultivars showed no significant effect of pruning treatments on development of either fruit or leaf scab except for cultivar Liberty in 2001 at one site. Pruning resulted in no consistent difference in the apple tree canopy microclimate. However, strong pruning resulted in improved spray deposition in the tree canopy when applications were made with an airblast sprayer at midsummer. Results are compared with similar studies, and their biological interpretation is discussed.

Summer Pruning as a Method for Reducing Flyspeck Disease on Apple Fruit.

Summer pruning of apples, as opposed to the conventional commercial practice of dormant pruning, consistently reduced the incidence of flyspeck on apple fruit by approximately 50% in each of 2 years in trees where no fungicides were applied. In commercial orchard blocks using fungicides, summer pruning also produced a slight but significant decrease in disease severity. There appear to be at least two mechanisms contributing to decreased flyspeck incidence and severity in summer-pruned apple trees. Summer pruning resulted in a small change in the apple canopy microclimate, decreasing the hours of relative humidity >95% in the canopy by 63% and increasing the evaporative potential. Summer pruning also resulted in improved spray deposition in the upper two-thirds of the tree canopy when applications were made with an airblast sprayer.

Within-canopy Spray Distribution from Fixed-wing Aircraft

We have evaluated two approaches to improve spray deposition within crop canopies from insecticide applications with fixed-wing aircraft. Both approaches involve increasing air velocity and turbulence in the crop canopy as a result of increased wake intensity and are expected to result in increased spray deposits within the canopy. One approach was to increase wake intensity with slower airspeed than normally used. The second approach was to increase wake intensity with a modified boom equipped with Chimavir winglets. Spray deposits were measured from an agricultural aircraft with a conventional boom operated under normal conditions. Spray deposits were also measured from the same aircraft with boom and operational conditions modified to increase wake intensity. Results of deposit measurements from leaf washes and water-sensitive paper, both on the top and bottom of leaves, at the top and midway down in the crop canopy, show that a high percentage of spray is deposited on the top of leaves. The treatments with higher wake intensity increased deposits on the bottom of leaves up to 80% under certain conditions. However, the amounts were relatively low and the influence of these increases on control of whitefly in cotton and cantaloupe was not established because of low insect infestations.

Aerial Spray Deposition in Cotton

The effect of aerial application parameters on the deposition of water-based sprays on mid-season cotton canopies was evaluated in three field studies. Fluorescent dye tracer spray deposits were measured on cotton leaves and three different types of artificial samplers at the top and midway down in the plant canopy, and on ground-cover sheets between the cotton rows. Over 400 samples collected over three years provided sufficient data to determine the relationship of spray mixture rate, droplet size, droplet density, temperature, relative humidity, and wind speed to active spray ingredient deposition on the crop canopy. These studies show that droplet spectra and spray rate can be modified or adjusted by the applicator to improve spray deposition and distribution in broadleaf row crop canopies. Environmental factors shown to adversely influence deposition may be avoided by spray applicators to maintain deposition efficiency.

Air Carrier Technique for Row Crop Spraying Applications

ABSTRACT THIS study focuses on the problem of applying spray material to upper-plant, underside-leaf surfaces of corn and soybean plants. Aircraft and ground pressure-atomizer applications of spray solution were quantified. Percent coverage values were generally less than 1 % on the sampling locations. Flat and hollow cone nozzle air carrier units were developed and evaluated for spray application to the upper-plant, bottom leaf surface. The air carrier method tested within a shroud improved spray deposition to the entire plant by 100% for corn and 234% for soybeans. Deposition to the upper-plant, bottom leaf surface was increased by 900% and 400% for corn and soybean plants, respectively. Deposition uniformity was also improved with the air carrier method.