Droplet Deposition and Transfer in Coffee Cultivation Under Different Spray Rates and Nozzle Types

Abstract

Optimising spraying operations in coffee cultivation can enhance both application efficiency and effectiveness. However, no studies have specifically assessed droplet deposition on leaves adjacent to the spray application band—fraction of droplet deposition referred to as ‘transfer’ in this study. Therefore, this study aimed to quantify droplet deposition and transfer resulting from different application rates and nozzle types in coffee trees. The experiment was conducted in a factorial design including three application rates (200, 400, and 600 L ha⁻¹) and two nozzle types (hollow cone and flat fan), with four replicates. Deposition was quantified at multiple positions: two application sides (left and right), three sections of the plant (upper, middle, and lower), and two branch positions (inner and outer). Thus, all measurements across sides, plant sections, and branch positions were nested, resulting in correlated data that were analysed using linear mixed-effects models (lme4 package), with parameters estimated using the restricted maximum likelihood method. The flat fan nozzle achieved the highest reference deposition, particularly on outer canopy thirds, while spray transfer (~29% of total deposition) was mainly driven by operational factors. Hollow cone nozzles at 200 L ha⁻¹ minimized transfer while maintaining adequate deposition. Optimizing applications requires maximizing reference deposition and minimizing transfer, which can be achieved through operational adjustments, airflow management, and complementary strategies such as adjuvants, electrostatic spraying, or tunnel sprayers.

1. Introduction

Coffee is a globally important commodity of commercial, cultural, and historical importance, particularly for Brazil, its leading producer and exporter. Meeting the growing demand for coffee through sustainable production presents challenges [1], as productivity depends on a complex interplay of various factors, especially agricultural management practices. In this context, spraying of plant protection products is a key practice shaped by plant protection needs, crop size, and pest dynamics, all of which affect application efficiency. However, achieving uniform distribution remains a challenge for traditional agricultural spraying methods. Uniform coverage of plant protection products is essential for both effective pest and disease control and for ensuring environmental sustainability [2,3]. Therefore, uneven droplet deposition across different parts of the plant can directly affect agricultural productivity. In coffee cultivation, pests and diseases can cause substantial yield losses, with reductions ranging from 26% to 38% when control practices are inadequate [4]. These impacts highlight the importance of achieving effective spray deposition throughout the vertical canopy profile.

Despite the availability of advanced spraying techniques for perennial crops [5,6], low-cost equipment, such as knapsack, hydraulic, pneumatic, and air-blast sprayers still predominate in Brazilian coffee farming. The underutilisation of advanced sprayers is linked to high acquisition costs, need for skilled labour, and predominance of small and medium-sized farms. In addition, the lack of public incentive policies and the challenging topography of many coffee regions further restrict adoption of high-tech sprayer. In this scenario, optimising operational conditions, including appropriate nozzle selection, application rates, travel speeds, regulation, calibration, and airflow regulation-becomes essential for efficiency [7].

In mechanized coffee plantations, axial-fan air-blast sprayers are the predominant technology. These machines generate large volumes of turbulent air at relatively low static pressures, but their adjustment capacity is limited, often resulting in excessive spray losses outside the canopy [8,9,10]. In contrast, tunnel-type sprayers allow precise spray targeting, minimize drift, and recycle excess spray, leading to grater deposition uniformity and reduced pesticide use [5,11,12]. However, these systems remain costly and are best suited for flat areas or uniform orchards.

In addition, when sprayer adjustments and calibration are not aligned with the target, they can result in uneven application, increased loss of spray to the ground, drift, and droplet evaporation [13]. In perennial crops, droplets are directed by airflow across the canopy and upward, leading to both horizontal drift across the canopy and vertical drift above the canopy and into the atmosphere. Therefore, it is crucial to minimise pesticide loss, under-application, over-application, and off-target deposition. These measures would help to protect the environment and human health and ensure food safety [10,14].

The performance of air-blast sprayers depends on the airflow requirements of the tree canopy. Therefore, the air delivery rate of sprayers must be appropriately regulated. However, field testing of these sprayers requires considerable effort, time, and expensive instruments to accurately measure airflow rates [15,16]. Moreover, spray behaviour and air velocity profiles within and around crop canopies remain poorly understood. Few farmers possess the knowledge needed to select and configure sprayers to address issues related to spray penetration and improve canopy depth deposition [17] without over-spraying beyond the target area. This limited knowledge and training among cultivators often result in suboptimal use of air-blast sprayers, with only a fraction of the product reaching the intended target and approximately 30–50% loss to non-target areas [18,19].

Air-assisted applications are designed to direct a droplet-laden air stream towards the canopy for deposition on the target. Insufficient flow results in poor penetration into the canopy, leading to inadequate deposition and reduced effectiveness of the control measures. In contrast, excessive airflow propels droplets beyond the intended range, causing soil and environmental losses and compromising application uniformity and target coverage [9,20]. Thus, restricting droplet distribution within the designated application range is crucial. Various studies have examined factors influencing foliar deposition or retention, such as nozzle type, application rates, and the use of adjuvants, with a focus on reducing drift, but few have addressed the comparative performance of nozzles types. Flat fan nozzles exhibit lower drift potential and provide a more uniform deposition than hollow cone nozzles [21,22,23]. In perennial crops, hollow cone nozzles are commonly used at high pressures, generating fine droplets that are more susceptible to loss [24]. Therefore, further investigations into the appropriate use of nozzle fan type are warranted [25].

Although significant progress has been made in application technology, studies on droplet deposition on leaves adjacent to the application band remains unexplored. This off-target droplet deposition, referred to as ‘transfer’ in the present study, represents an induced and tolerated form of droplet displacement within the field. Unlike drift, which occurs off-side, transfer occurs within the cropped area and may induce local overdosing, potentially accelerating resistance selection in pests and pathogens. Therefore, we aimed to quantify deposition patterns in coffee trees across two fractions of the directly sprayed area under different nozzle types and application rates, thereby providing insights into canopy droplet distribution dynamics and the risks of overdosing associated with in-field transfer.

2. Materials and Methods

This study was conducted on the Jataí property (18°53′04.82′′ S, 47°21′09.15′′ W), located at an altitude of 972 m, in the municipality of Monte Carmelo-MG, Brazil, in February 2023. This region is characterised by a Cwa (warm and humid with a dry winter) climate according to the Köppen–Geiger classification [26]. Laboratory analyses were carried out at the Centre of Excellence in Agricultural Mechanisation, affiliated with the Institute of Agricultural Sciences at the Federal University of Uberlândia, Brazil.

The trial was conducted in a 6-year-old coffee plantation of Mundo Novo cultivar, with a plant spacing of 3.8 × 0.6 m. The plants were in the fruit-filling stage, with an average height of 2.75 m, a crown diameter of 1.64 m, and a vegetation volume of 11,868 m ha⁻¹, calculated using the methodology adapted from [27]. Each experimental unit (1260 m²) used for treatment applications comprised 10 planting rows that are 40 m long. A central 20 m section of two planting rows was designated as the effective area, with 10-m sections at both ends serving as borders.

The experiment was conducted in a factorial design (3 × 2) including three application rates (200, 400, and 600 L ha⁻¹) and two nozzle types (hollow cone and flat fan), with four replicates. Deposition was quantified at multiple positions: two application sides (left and right), three sections of the plant (upper, middle, and lower), and two branch positions (inner and outer). Thus, all measurements across sides, plant sections, and branch positions were nested, resulting in correlated data.

The response variable was tracer deposition on the leaves in the directly sprayed area, measured at various locations (sides, thirds, and positions). Tracer deposition was assessed in Fractions 1 and ½, as described in ISO 22866 [28]. Depositions measured in Fraction 1 were referred to as ‘reference’, while those in Fraction ½ were designated as ‘transfer’ (Figure 1).

Treatments were randomised based on the application rate and nozzle type. Additional treatments were organised hierarchically within the application area defined by the combination of these treatments (3 × 2) and included application side, third of the plant, and branch position (Figure 2).

The application was conducted using an air-blast sprayer model Arbus 2000 TF 2P (Jacto, Pompeia, São Paulo, Brazil), with a tank capacity of 2000 L. The air-blast sprayer featured 12 nozzle holders on each side arch, a piston pump delivering a flow rate of 75 L min⁻¹, and an axial-flow fan with a diameter of 850 mm positioned 1.10 m above ground level. The fan operated at an air speed of 26 m s⁻¹, producing an air volume of 11.2 m³ s⁻¹. The fan blades were set to position ‘A’, which provides maximum air flow and is the standard configuration used by coffee farmers in the region.

The tractor used was a 4 × 2 FWD Auto model 4265 compact tractor (Massey Ferguson, Itu, São Paulo, Brazil) with a power output of 65 hp. The power take-off speed was set at 540 rpm, using an MDT2238A digital tachometer (Minipa^®, Santo Amaro, São Paulo, Brazil). The tachometer remained fixed at 1980 rpm, and the tractor operated in third gear at a speed of 6.45 km h⁻¹ across all treatment areas.

Application rates were calibrated by adjusting the working pressure of the air-blast sprayer to match that of the hydraulic nozzle. Calibration was performed using a pressure gauge kit and a 1000 mL graduated beaker. Hollow cone nozzles with an 80° spraying angle, traditionally used in coffee farming, and flat fan nozzles with a 110° spray angle, known for producing fine droplets, were selected for the experiment (

Table 1. Description of treatment application rates, nozzle types and corresponding operating conditions—used for spray deposition on coffee plants.

Treatment	Rate (L ha−1)	Nozzle Type	Tip	Flow (L min−1)	Pressure (kPa)
1	200	Flat fan nozzle	BD 01	0.34	207
2	400	Flat fan nozzle	BD 02	0.68	207
3	600	Flat fan nozzle	BD 025	1.02	289
4	200	Hollow cone nozzle	MAG 1	0.34	413
5	400	Hollow cone nozzle	MAG 1.5	0.68	723
6	600	Hollow cone nozzle	MAG 2	1.02	1.034

).

The coefficients of variation for the left and right booms were 2.52% and 2.27%, respectively, based on the flow rate of ISO 5682-1 standards [29]. The application was uniform on each side, with tip flow rate variation remaining below 10%, in accordance with the standard recommendations.

The spray mixture comprised water and the food tracer Brilliant Blue (FD&C Blue No. 1), applied at a rate of 600 L ha⁻¹. The required tracer concentrations were adjusted to 3.0, 1.5, and 1.0 g L⁻¹ for application rates of 200, 400, and 600 L ha⁻¹, respectively. Weather data during the application were obtained from a Vantage Pro2 weather station (Davis, Hayward, CA, USA), which recorded a temperature of 28.4 °C, a relative humidity of 66%, and a wind speed of 2.4 km h⁻¹, predominantly in an easterly direction.

The application commenced with a single pass of the air-blast sprayer targeting only the reference fraction. Leaves were collected 15 min after application to allow adequate settling of the tracer. To assess deposition, leaves were collected from both the reference and transfer fractions. Specifically, two pairs of leaves were sampled from the plagiotropic branch of a single plant in each section (upper, middle, and lower), obtained from both the inner and outer sides of the canopy. The leaves were placed in pre-labelled plastic bags, stored in Styrofoam boxes for thermal and light insulation, and transported to the laboratory for tracer quantification.

In the laboratory, 20 mL of distilled water was added to the plastic bags to remove the tracer. The solution was then transferred to a plastic container and stored in the dark for 24 h to allow impurities to settle. Subsequently, the absorbance of each sample was measured at 630 nm using a V-5000 spectrophotometer (Metash^®, Songjiang District, Shanghai, China). The tracer concentration was determined based on the absorbance using a calibration curve. The tracer mass on the leaves was calculated based on the initial spray concentration applied in the field and the dilution volume of the samples. Leaf area was measured using an LI 3100C leaf area metre (LI-COR, Lincoln, NE, USA).

Statistical analyses were performed using RStudio software version 4.3.1 [30]. The dataset was checked for outliers using boxplots. A linear mixed model (LMM) was fitted using the lme4 package [31], with parameters estimated via the restricted maximum likelihood. LMMs account for both fixed and random effects and are well suited to the hierarchical structure of the experiment. In complex experimental designs, particularly when independence among observations is not assured, mixed models enhance the accuracy of predictions by accommodating sources of variation introduced by influencing variables. Assumptions of homoscedasticity, normality, linearity, and independence were validated by analysing quantile-quantile plots of the normalised residuals and plotting the residuals against the explanatory variables and fitted values [32]. Interactions among the application rate, nozzle type, third of the plants (lower, middle, and upper), branch position (internal and external), and their individual effects were considered as fixed factors for the model. The hierarchical structure of the dataset, which accounted for the plant third within each application side and the application area (block), was treated as random factor. When significant differences were detected, estimated means of the factors were compared using Tukey’s test at a 5% significance level, with Sidak adjustment, using the emmeans package [33].

3. Results

3.1. Deposition in the Reference Fraction Across Nozzle Types and Application Rates

In the reference fraction, for the flat fan nozzle, deposition was the highest at an application rate of 400 L ha⁻¹, intermediate at 200 L ha⁻¹, and the lowest at 600 L ha⁻¹. In contrast, the hollow cone nozzle exhibited the highest deposition at 600 L ha⁻¹, followed by 200 L ha⁻¹, and the lowest deposition at 400 L ha⁻¹. Notably, at 400 L ha⁻¹, the flat fan nozzle achieved 75% greater deposition than the hollow cone nozzle. However, deposition did not differ significantly between the two nozzle types at the other application rates (Figure 3).

3.2. Deposition in the Reference Fraction at Different Positions on the Plagiotropic Branch

Deposition was significantly higher on the outer canopy, averaging 130% more than the inner side, regardless of application rate or nozzle type (Figure 4).

The deposition on the side of the plant facing the reference fraction was higher at the outer position of the branch than at the inner position. In contrast, on the opposite (transverse) side of the plant, the highest tracer concentration was observed at the inner position.

3.3. Deposition in the Reference Fraction as a Function of Application Rates in the Application Sides and Canopy Thirds

The highest deposition in the reference fraction occurred in the top third of the canopy on the right side at the 200 L ha⁻¹ application rate (Figure 5). On the lower third of the left side, deposition was the highest at an application rate of 600 L ha⁻¹. Notably, deposition was uniform across the thirds only on the left side at an application rate of 200 L ha⁻¹. Generally, deposition decreased with increasing canopy height; however, this trend was observed only on the left side at an application rate of 600 L ha⁻¹. In contrast, on the right side, at an application rate of 200 L ha⁻¹, deposition increased with canopy height. In terms of application sides, deposition was high on the right side in the upper third at application rates of 200 and 600 L ha⁻¹, and in the middle third at 400 L ha⁻¹.

Deposition on the upper right side was higher than that on the left side. This finding can be attributed to the alignment of the plagiotropic branch with the airflow on the right side, which was directed downward. In contrast, on the left side, the airflow was directed upwards, encountering more resistance when it collided with the branches.

3.4. Transfer Through the Sides of the Application Boom

Figure 6 illustrates the interactions among the nozzle type, application rate, and application side for transfer. Differences in transfer were observed between hollow cone and flat fan nozzles at the 400 L ha⁻¹ application rate on the left side, and at the 200 and 400 L ha⁻¹ rates on the right side. For both nozzle types, the highest transfer occurred at the 200 L ha⁻¹ rate, but only on the right side, whereas low transfer occurred at both the 400 and 600 L ha⁻¹ rates. At the 400 L ha⁻¹ rate, the flat fan nozzles resulted in greater transfer on the left side than that observed at the 600 L ha⁻¹ rate. Overall, spray transfer was uniform between the application sides, albeit slightly higher on the right side when using the flat fan nozzle at the 200 L ha⁻¹ application rate.

3.5. Transfer at Inner and Outer Canopy Positions

At both branch positions, the flat fan nozzles resulted in a higher transfer than the hollow cone nozzle at the 400 L ha⁻¹ application rate. However, at the 200 L ha⁻¹ application rate, this difference was only observed at the inner position. The flat fan nozzle generated higher transfer at both branch positions at the 200 and 400 L ha⁻¹ application rates than that at the 600 L ha⁻¹ rate. Transfer at the outer position was higher than that at the inner position, only at the 200 L ha⁻¹ application rate with the hollow cone nozzle (Figure 7).

The interaction between the 400 L ha⁻¹ application rate and the hollow cone nozzle resulted in decreased transfer at both branch positions, but low deposition in the reference fraction. Overall, transfer was similar across branch positions. The highest reference deposition was observed with the flat fan nozzle at the 400 L ha⁻¹ application rate, followed by the flat fan nozzle at 200 L ha⁻¹, and the hollow cone nozzle at 200 L ha⁻¹. Only the combination of the 200 L ha⁻¹ application rate and the hollow cone nozzle results in high transfer at the outer position, recording 85% and 15% higher transfer than that at the 400 L ha⁻¹ and 600 L ha⁻¹ application rates, respectively.

Transfer was also influenced by the nozzle type, with the flat fan nozzle generating higher transfer than the hollow cone nozzle. However, transfer was low at both branch positions at the 600 L ha⁻¹ application rate, likely owing to increased runoff, which also contributed to reduced deposition in the reference fraction.

4. Discussion

In Brazil, challenges associated with the application of crop protection products include sprayer calibration and the determination of the correct dosage for the spray tank. In coffee cultivation, the application range is defined by the spacing between planting rows, which influences both the application rate and droplet distribution. During application, the sprayed strip not only receives deposition of the active ingredient at the recommended rate but also experiences a fraction of transfer, which can spread to adjacent rows. This transfer can lead to overdosing, potentially contributing to the selection of resistant biotypes and altering pest population dynamics. Inaccurate dosing in crop fields is associated with concerns such as pest resistance, pesticide residues, and environmental contamination [34,35]. Thus, the implications of spray transfer extend beyond technical efficiency, as they are closely linked to environmental sustainability and regulatory frameworks.

Minimizing drift and overdosing is essential to reducing environmental contamination, pesticide residues, and nontarget impacts, while also enhancing economic sustainability by lowering input waste and improving the cost-benefit ratio for growers. However, research on droplet transfer to adjacent rows during spraying, specifically for coffee trees, is limited.

In the present study, we to relate tracer deposition in the transfer fraction to that in the reference fraction and demonstrated that the influence of the evaluated factors on deposition differed between the two fractions of the directly sprayed area. Our results showed that nozzle type and application rate exerted a greater effect on transfer deposition than the application side which influences the airflow dynamics. Excessive or improperly directed airflow can result in uneven application and increased chemical loss [36]. Although the heterogeneous airflow of the air-blast sprayer tends to cause uneven deposition between sides and among canopy thirds in the reference fraction, it did not significantly affect transfer. Droplets that crossed the first canopy layer in the reference fraction reached the transfer fraction with reduced kinetic energy, which promoted a more uniform distribution among canopy strata in this fraction, despite the overall lower deposition.

Our results indicate that droplet transfer is mainly governed by operational factors rather than by the airflow asymmetry generated by the sprayer fan between the sides of application. These findings suggest that fine-tuning operational parameters can optimize droplet penetration and minimize transfer deposition. Additionally, adjusting these variables according to canopy structure and plant developmental stage may further improve efficiency. Future studies could investigate whether transfer deposition becomes more relevant canopy densities and specific phenological stages, as well as explore complementary strategies, such as the use of adjuvants. Moreover, the integration of advanced technologies, such as Computational Fluid Dynamics (CFD) modelling, may provide valuable insights into airflow patterns and droplet trajectories within dense canopies [37,38], supporting more precise operational adjustments that enhance reference fraction deposition while simultaneously mitigating transfer fraction and drift.

The barrier effect of external leaves plays a critical role in reducing droplet penetration into the inner canopy, this phenomenon is particularly evident in dense canopies, where droplets deposit on the first surface encountered, limiting coverage of internal regions and compromising application efficiency. Plant architecture complicates airflow dynamics within and around the canopy When the airflow passes through the canopy, its energy is altered, which affects the distribution of droplets that deposit on the leaves [39]. Canopy structure and leaf area density strongly influence droplet behaviour in the internal canopy. Adjusting airflow according to canopy architecture, leaf density, and growth stage enhances pesticide use efficiency [40], particularly regarding deposition in the internal portion of the reference fraction. Thus, electrostatic spraying can support improved deposition in internal canopy positions, while reducing losses and enabling more precise applications [41].

We observed the highest deposition in the reference fraction in the lower third of the canopy at the highest application rate (600 L ha⁻¹). This result is consistent with that of [42], who noted that a high application rate (560 L ha⁻¹) combined with high turbine speed improves the mobility of coffee leaves, overcoming challenges posed by overlapping foliage. In contrast, the upper third of the coffee canopy, being the farthest from the nozzle types, presents challenges for effective product deposition [43].

The variability observed in the reference deposition fraction across sides and thirds can be attributed by the physical interactions between airflow dynamics and canopy architecture. As the sprayed air penetrates the canopy, the ability of droplets to reach different strata is reduced. These processes, combined with fine droplet size and surface tension, determine foliar retention efficiency and highlight the complex interactions involved. Other studies have demonstrated that the right side of the canopy receives higher air velocity due to the direction of turbine rotation, leading to increased deposition, whereas greater penetration into the middle third of the plant occurs on the left side owing to the horizontal persistence of airflow [44,45]. Notably, the variability in reference deposition among canopy thirds is greater than that observed between application sides, highlighting the need to stratify plants into thirds when measuring tracer retention on leaves. Therefore, beyond achieving uniform distribution during application, consistent deposition across the canopy thirds must also be considered to minimise the risk of overdosing.

The air and droplet clouds generated by the air-blast sprayer initially contacted the side of the plant facing the spray passage, depositing the product on the outside of the branch before reaching the inside. The airflow then dissipated within the canopy; however, transfer continued, resulting in product deposition on the side of the plant adjacent to the spray passage. This overlap allows the product to be deposited on areas that were already treated. Moreover, approximately 29% of the tracer was directed towards the transfer areas.

Our results indicated that deposition in the reference fraction with the lowest transfer occurred at an application rate of 200 L ha⁻¹ with a hollow cone nozzle. In contrast, this sample application rate with a flat fan nozzle resulted in considerable carry-over. The flat fan nozzle yielded greater deposition than the hollow cone nozzle, as it operates at lower working pressures. In contrast, hollow cone nozzles function at higher pressures, producing finer droplets that follow a more tortuous and slower path to the target. These finer droplets are more prone to drift, reinforcing the need for proper operational adjustments and the potential use of adjuvants to improve deposition efficiency [46,47]. Spray pressure is a critical factor influencing droplet size and coverage, thereby affecting drift and deposition [48]. Although we did not directly investigate spray pressure as a variable in this study, its effect can be inferred from the observed differences in pressure values among treatments.

In the present study, we did not compare efficiency between air-assisted sprayers. Nevertheless, our results suggest that tunnel sprayers may represent a viable alternative for mitigating droplet redistribution. Axial fan sprayers direct the spray to only one side of the plant, whereas tunnel sprayers spray on both sides and may include collectors to recover and recycle excess spray that does not reach the target plant. Tunnel sprayers also improve coverage and uniformity, reduce drift and off-target deposition, and increase the total application rate per cultivated area [6,7,49].

From an agronomic perspective, heterogeneous deposition among canopy strata compromises pest and disease control in coffee cultivation. Excessive deposition resulting from droplet transfer can lead to overdosing in certain canopy regions increasing the risk of phytotoxicity and chemical waste. At the same time, irregular deposition patterns may expose pest populations to inconsistent doses, accelerating the development of resistance. Therefore, optimizing deposition is essential not only for ensuring effective crop protection but also to minimize the negative impacts of overdosing and to prolong the useful life of active ingredients.

Overall, our study demonstrated that accurately measuring transfer during spraying could drive substantial advancements in the air-blast sprayer industry. While applications can be optimised from both technical and environmental perspectives, the use of appropriate machinery remains crucial for ensuring effective application. Therefore, future studies should focus on developing strategies and machines that improve the targeting and retention of plant protection products on the intended fraction, reducing droplet drift and redistribution.

5. Conclusions

This study demonstrated that spray deposition in coffee canopies is strongly influenced by the interaction between nozzle type, application rate, and plant architecture, Flat fan nozzles provided the highest deposition in the reference fraction, which was greater on the outer canopy thirds and application sides, highlighting the barrier effect of external leaves and the special heterogeneity of deposition.

Spray transfer accounted for approximately 29% of the toral deposition and was predominantly determined by operational factors, including nozzle type and application rate. Flat fan nozzles generally produced higher transfer than hollow cone nozzle, whereas the hollow cone nozzle at 200 L ha⁻¹ minimized transfer while maintaining sufficient deposition in the reference fraction.

The average reference deposition was 0.89 μgcm⁻², with transfer at 0.36 μgcm⁻². Research on air-blast sprayer applications addressing droplet deposition in the directly sprayed area, aiming to prevent application failures and overspraying, remains limited. Additional studies are needed to evaluate the influence of application technology variables in conjunction with transfer under different operational conditions, particularly considering airflow, plant developmental stage, and the efficacy of phytosanitary products.

Overall, optimizing applications requires not only maximizing deposition in the reference but also minimizing transfer. This study highlights the potential of operational adjustment, airflow management according to plant structure, and complementary strategies, such as the use of adjuvants, electrostatic spraying, and tunnel sprayer, to enhance deposition efficiency.