Abstract: The present study compared entomopathogenic nematode delivery at the base of savoy cabbage and cauliflower, at the lower side of savoy cabbage and cauliflower leaves and in leek stems and the ground deposition using a five-nozzle spray boom equipped with an ISO 08 flat fan, an air induction flat fan and Twinjet spray nozzles. Additionally, an air support system and a row application system were evaluated.
Abstract: Flemish greenhouse growers predominantly use handheld spray guns and lances for their crop protection purposes despite the heavy workload and high risk for
operator exposure associated with these techniques. These spray application techniques have also shown to be less effective than spray boom equipment under many conditions. Handheld spraying techniques are less expensive, however, and they are more flexible in practical use. Many growers also erroneously believe that high spray volumes and pressures are needed to assure good plant protection. The aim of this work was to evaluate the spray deposition, penetration, and uniformity between a manually pulled horizontal spray boom as compared with a spray gun under controlled laboratory conditions. In this study, we evaluated six spray application techniques, i.e., three spray boom and three spray gun techniques. In general, the deposition results were comparable between the spray boom and the spray gun applications. The spray boom applications, however, resulted in a more uniform spray distribution. At the plant level, the spray distribution was not uniform for any of the techniques used; the highest deposits were observed on the upper (or adaxial) side of the top leaves. Using spray guns at a higher spray pressure did not improve spray penetration in the canopy or deposition on the bottom (or abaxial) side of the leaves. Of the different nozzle types tested on the spray boom, the extended range flat fan XR 8003 gave the best results. Crop density clearly affected crop penetration and deposition on the bottom side of the leaves.
Abstract: Fractal scaling of the exponential type is used to establish the cumulative volume (V) distribution applied through agricultural spray nozzles in size x droplets, smaller than the characteristic size X. From exponent d, we deduced the fractal dimension (Df) which measures the degree of irregularity of the medium. This property is known as ‘self-similarity’. Assuming that the droplet set from a spray nozzle is self-similar, the objectives of this study were to develop a methodology
for calculating a Df factor associated with a given nozzle and to determine regression coefficients in order to predict droplet spectra factors from a nozzle, taking into account its own Df and pressure operating. Based on the iterated function system, we developed an algorithm to relate nozzle types to a particular value of Df. Four nozzles and five operating pressure droplet size characteristics were measured using a Phase Doppler Particle Analyser (PDPA). The data
input consisted of droplet size spectra factors derived from these measurements. Estimated Df values showed dependence on nozzle type and independence of operating pressure. We developed an exponential model based on the Df to enable us to predict droplet size spectra factors. Significant coefficients of determination were found for the fitted model. This model could prove useful as a means of comparing the behavior of nozzles which only differ in not measurable geometric parameters and it can predict droplet spectra factors of a nozzle operating under different pressures from data measured only in extreme work pressures.
Abstract: BACKGROUND
Fewer plant protection products are now authorized for use in ornamental growings. Frequent spraying with the same product or a suboptimal technique can lead to resistance in pests and diseases. Better application techniques could improve the sustainable use of the plant protection products still available. Spray boom systems - instead of the still predominantly used spray guns – might improve crop protection management in greenhouses considerably. The effect of nozzle type, spray pressure and spray angle on spray deposition and coverage in ivy pot plants was studied with a focus on crop penetration and spraying the bottom side of the leaves in this dense crop.
RESULTS
The experiments showed a significant and important effect of collector position on deposition and coverage in the plant. Although spray deposition and coverage on the bottom side of the leaves is generally low, deposition and coverage could be improved with a factor 3.0 to 4.9 using the appropriate application technique.
CONCLUSIONS
Using a spray boom in a dense crop, the nozzle choice, spray pressure and spray angle should be well considered. The hollow cone, the air inclusion flat fan and the standard flat fan nozzle with an inclined spray angle performed best because of the effect of, respectively, the swirling droplets, the droplets with a high momentum and the droplet direction.
Abstract: Due to the decreasing availability of authorized plant protection products, adequate pest control has become more difficult in many ornamentals. Although much attention is given to predatorÂ]pest interactions in integrated control, almost no research is available about the optimization of spray application techniques in ornamentals. Yet, spray boom systems, instead of the still predominantly used spray guns, might improve crop protection management in greenhouses considerably. Spray application technique will influence the spray deposition and as such its efficiency. In this study, the effect of air support and spray angle (Â]30‹, 0‹, 30‹) on spray deposition in ivy pot plants was tested using a coarse droplet spray nozzle (Lechler ID 90 02 at 6.0 bar). Spray deposition was measured using a quantitative method (mineral chelates). Spray coverage was assessed by a visual method using waterÂ]sensitive paper. All applications were performed in the laboratory with a fully automated spray system. Spray deposits were measured at three plant levels on the top and on bottom sides of leaves, together
with offÂ]target depositions. The use of air support improved crop penetration and deposition on the bottom sides of the leaves and reduced spray deposition in the top layer on the top sides of the leaves, resulting in a more uniform spray distribution over the crop canopy. The effect of air support on crop penetration was most pronounced with the standard 0‹ spray angle. Without air support, spray angling improved crop penetration but not the deposition on the bottom sides of the leaves.
Abstract: There are many methods available for sampling spray drift, and a great variety of estimates of spray drift have been published. Available data on spray drift were collected from different studies and the measurements of spray drift were analysed to determine similarities and differences between the individual studies. Each of the methods varied significantly in their estimates of spray drift. This variation was due to many factors that differed between the published sources, such as environmental conditions, cropping system, equipment used and the tracer used. It is suggested that in order to compare drift measurements between published studies, measurement techniques and sampling distances must be standardised, and environmental conditions (humidity and temperature) should be restricted to within certain boundaries in the field, and controlled within artificial tests, unless, of course, the effect of this variable on drift is being examined.
Abstract: Spray drift continues to be a major problem in applying agricultural pesticides. This article summarizes the results of a fiveÂ]year study of drift from field crop sprayers using a unique integrated approach. Indirect (spray quality and wind tunnel measurements) and direct (field) drift experiments were performed, and drift models were developed to study the effect of spray application technique, droplet characteristics, buffer zones, meteorological conditions, spray liquid properties, border structures, and crop characteristics on drift from field crop sprayers. It was found that indirect drift measurements can be a valuable alternative to field drift experiments. A validated 3Â]D computational fluid dynamics (CFD) mechanistic drift model was developed, which can be used for a systemic study of different influencing factors. This model was reduced to a fast 2Â]D diffusion advection model, which is useful as a hands-]on drift prediction tool. From the experiments as well as from the models, the fraction of small droplets and the spray boom height were found to be the most influential spray application factors. Moreover, meteorological conditions as well as crop characteristics have an important effect on the amount of spray drift, which can be reduced significantly using intercepting screens or buffer zones. From this study, drift protocols, data, and models are made available, which help to understand and reduce the complex phenomena of spray drift.
Abstract: Application technology for biological insecticides like entomopathogenic nematodes (EPN) has been relatively neglected. One of the major considerations related to the selection and use of an application system is the application distribution pattern. A completely uniform distribution of the nematodes in soil applications is not essential because the nematodes can move over short distances; however, a uniform distribution is important in foliar EPN applications. The
present study examined the volumetric distribution pattern of Steinernema feltiae beneath single standard flatâ€fan, airâ€induction, deflector, and TwinJet spray nozzles. A comparison with the distribution of a chemical tracer was made to reveal possible distribution problems. Droplet size spectra of the nozzles were measured and linked with the distribution results. A theoretical calculation of the coefficient of variation of the nematode distribution beneath a spray boom was performed. Finally, the actual spray pattern of the EPN on a horizontal surface beneath a spray boom was studied. We can conclude that the volumetric distribution pattern of EPN is influenced by nozzle type and is different from the volumetric distribution pattern of a chemical compound beneath a TT 110 08 deflector nozzle. The spray overlap from a spray boom decreases differences in nematode distribution to an acceptable level. Nozzle type significantly influences the number of nematodes deposited on a horizontal Petri dish and their distribution within the droplets. Future experiments are needed to reveal if the measured differences in deposition and coverage due to nozzle type will result in significant differences in pest control.
Abstract: Damage caused to entomopathogenic nematodes by spray application is generally assessed by observing the viability of the infective juveniles (IJ) under the microscope. To improve the quality and speed of this observation we developed an image processing technique and tested the efficacy of acetic acid and sodium chloride as chemical stimulants. Because of the lower standard error on the results obtained (0.7 vs 1.7) sodium chloride was eventually selected for all following observations. The viability as observed with the image processing technique rose significantly with the time after suspending the nematodes in water; however, viability as observed under the microscope was not influenced by the time. These differences can be attributed to the difference in type of stimulant (mechanical vs chemical) used. Three hours and a half after suspending the nematodes, the viability as measured using the image processing system was still significantly lower than the viability as measured under the microscope. This difference did not disappear after 24h at 4, 15 or 24°C. Preservation during 24h at 35°C significantly decreased the viability with 5.9% (microscope) or 11.0% (image processing technique). The decrease in viability as observed with the image processing system corresponded better with the decrease in infectivity (i.e. 13.8%). Our results support further use of the image processing technique, not only to observe the viability of entomopathogenic nematodes but also to count the mobile or total number of any nematode species.
Abstract: The application of entomopathogenic nematodes (EPN) is generally done using standard spray application techniques. However, in contrast to chemical pesticides, these biological antagonists must remain viable during and after the application process. For the application of EPN, a good agitation system is indispensable as the nematodes tend to sediment fast in a spray tank without agitation. Three agitation systems, viz. mechanical, pneumatic and hydraulic agitation were tested for their ability to keep Steinernema carpocapsae (Rhabditida: Steinernematidae) suspended in an undamaged way. Hydraulic agitation was tested using a centrifugal and a diaphragm pump. Nematode damage was quantified based on viability and infectivity of the EPN. The ability of the agitation system to keep the nematodes in suspension was examined by comparing the nematode concentration observed in the samples taken at different agitation times. Only the hydraulic agitation using the centrifugal pump damaged the nematodes. After 120 minutes of recirculation, only 19.3% of the nematodes survived. Infectivity was even reduced to 0%. An additional experiment revealed that the temperature rise, from 21.7° to 45.4°C, was responsible for the observed nematode damage. The concentration measurements showed that the pneumatic agitation was unstable. Agitation during 120 minutes using the other agitation systems resulted in a significant loss of nematodes at 15 cm above the spray tank bottom. In conclusion, mechanical and hydraulic agitation using a diaphragm pump can be recommended when S. carpocapsae is applied, although attention should be paid to possible nematode loss during application.
Abstract: BACKGROUND
Increasingly, Flemish greenhouse growers use spray booms instead of spray guns to apply plant protection products. Although the advantages of spray booms are well known, growers still have many questions concerning nozzle choice and settings. Spray deposition using a vertical spray boom in tomatoes and strawberries was compared with the reference spray equipment. Five different settings of nozzle type, size and pressure were tested with the spray boom.
RESULTS
In general, the standard vertical spray boom performed better than the reference spray equipment in strawberries (spray gun) and in tomatoes (air assisted sprayer). Nozzle type and settings significantly affected spray deposition and crop penetration.
Highest overall deposits in strawberries were achieved using air inclusion or extended range nozzles. In tomatoes, the extended range nozzles and the twin air inclusion nozzles performed best. Using smaller size extended range nozzles above the recommended pressure range resulted in lower deposits, especially inside the crop canopy.
CONCLUSIONS
The use of a vertical spray boom is a promising technique for applying plant protection products in a safe and efficient way in tomatoes and strawberries and nozzle choice and setting should be well considered.
Abstract: The drift characteristics of 10 different spray nozzles were tested using three contrasting drift risk assessment means namely phase Doppler particle analyser (PDPA) laser measurements, wind tunnel measurements (both indirect drift risk assessment means) and field drift experiments (direct drift risk assessment means). The effect of nozzle size (ISO 02, 03 04 and 06) and nozzle type (standard flat-fan, pre-orifice flat-fan, air-induction) on droplet characteristics, drift potential and field drift were studied. A comparison was made between the results from the indirect and direct measurements to evaluate their potential for predicting the losses occurring from pesticide drift from field crop sprayers. In total, 90 PDPA laser measurements, 46 wind tunnel experiments and 61 field drift experiments were carried out with 10 different spray nozzles at a pressure of 300 kPa. The reference spray application for the field measurements was defined as a Hardi ISO F 110 03 standard flat-fan nozzle at a pressure of 300 kPa with a nozzle or boom height of 0.50 m and a driving speed of 8 km.h-1; conditions that were always used for the comparative assessments of the different nozzle-pressure combinations.
Results showed that with the indirect risk assessment means (wind tunnel and PDPA laser measurement), driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and that both methods are suitable for relative assessments of drift risk. Measuring the proportion of the total volume of droplets smaller than 75 ïm diameter was best suited to represent the drift reduction potential in the field with different nozzle-pressure combinations. This was followed by the wind tunnel approach numerically integrating the measured fallout deposit curve. Both wind tunnel approaches for measuring airborne spray gave inferior results. Based on these indirect drift measurements and a statistical drift prediction equation for the reference spraying, it was possible to come to a realistic estimate of field drift data at a driving speed of 8 km h-1 and a boom height of 0.50 m.
Abstract: Correct field drift prediction is a key element in environmental risk assessment of spraying applications. A reduced order drift prediction model based on the diffusion-advection equation is presented. It allows fast assessment of the drift potential of specific ground boom applications under specific environmental wind conditions that obey the logarithmic wind profile. The model was calibrated based on simulations with a validated Computational Fluid Dynamics (CFD) model. Validation of both models against 38 carefully conducted field experiments is successfully performed for distances up to 20 m from the field edge, for spraying on flat pasture land. The reduced order model succeeded in correct drift predictions for different nozzle types, wind velocities, boom heights and spray pressures. It used 4 parameters representing the physical aspects of the drift cloud; the height of the cloud at the field edge, the mass flux crossing the field edge, the settling velocity of the droplets and the turbulence. For the parameter set and range considered, it is demonstrated for the first time that the effect of the droplet diameter distribution of the different nozzle types on the amount of deposition spray drift can be evaluated by a single parameter, i.e., the volume fraction of droplets with a diameter smaller than 191 pm. The reduced order model can be solved more than 4 orders of magnitude faster than the comprehensive CFD model. (C) 2008 Elsevier Ltd. All rights reserved.
Abstract: BACKGROUND: Operator safety is still one of the main problems concerning greenhouse spray applications in South European horticulture. The main objective of this study was to compare potential dermal exposure (PDE) between traditional handheld spray application techniques (i.e. a standard spray gun walking forwards, a spray lance walking forwards and backwards) and novel spray application techniques with spray booms (i.e. a trolley, the Fumimatic and the Fumicar). RESULTS: PDE varied from 19.7 mL h(-1) for the Fumimatic to 460 mL h(-1) for the spray lance walking forwards. Walking backwards reduced PDE by a factor 7. With the trolley, Fumimatic and Fumicar, PDE was respectively 20, 60 and 8 times lower than with the standard spray gun. With the spray lance, PDE was about 2.5 times higher than with the spray gun. Pesticide distribution over the operator's body was non-uniform and correlated strongly with the application technique. With the traditional techniques, exposure to the legs and feet represents 60-80% of the total exposure. CONCLUSIONS: Novel spray application techniques using spray booms greatly decrease operator exposure because the operator is not walking directly into the spray cloud and the sprayed crop, and because of their higher capacity. Depending on the type of spray application, different parts of the body need to be protected most.
Abstract: 46 wind tunnel measurements were used to measure airborne and fallout spray volumes for 10 different spray nozzles. Drift potential reduction percentages (DPRP), expressing the reduction of the drift potential compared with the reference spraying, were calculated using the following three different approaches; DPRPV1 was based on calculating the first moment of the airborne spray profile, DPRPV2 integrating the airborne spray profile, and DPRPH integrating the fallout deposit curve.
The results showed the expected fallout and airborne spray profiles. For the standard flat-fan nozzles, DPRPV1 values were the highest followed by DPRPV2 and DPRPH. For the low-drift nozzles the opposite trend was found. The larger the ISO nozzle size, the higher the DPRP values for both these nozzle types. For the air-inclusion nozzles, there was close agreement between DPRPV1, DPRPV2 and DPRPH values. This is important in the interpretation of wind tunnel data for different nozzle types and sampling methodologies.
Abstract: This research was on the effect of the physicochemical properties of the spray liquid on pesticide spray drift. Ten pesticide spray liquids with various physicochemical properties were selected for study. Some of these spray liquids were also examined with the addition of a polymer drift-retardant. In the first part, laboratory tests were performed to measure surface tension, viscosity, evaporation rate and density of the spray liquids. Subsequently, drift experiments were performed in a wind tunnel. From the results it was found that the dynamic surface tension is a major drift-determining factor, and also that the addition of a polymer drift-retardant can reduce drift significantly by increasing the viscosity. Drift reduction was found to be less effective with spray liquids of emulsifiable and suspendable formulation types than with spray liquids of water-dispersible granules and powders.
Abstract: Due to the decreasing availability of authorized plant protection products, adequate pest control becomes more difficult in many ornamental crops and almost no information is available about the optimization of spray application techniques in ornamental crops. Yet, spray boom systems - instead of the still predominantly used spray guns – might improve crop protection management in greenhouses considerably. Application rate, nozzle type and configuration will influence the spray deposition and as such its efficiency. In this study, spray deposition in ivy pot plants [Hedera algeriensis cv. ‘Montgomery’, Hibb.], grown on hanging shelves in greenhouses was compared with a traditional spray gun with a disc-core nozzle and a manually pulled trolley equipped with two vertical spray booms. The sprayings with the spray gun were performed at an application rate of 8500 L•ha-1. For the vertical spray boom system, two different reduced application rates (2500 and 5000 L•ha-1) with five different combinations of nozzle type, size and pressure for each application rate were investigated. This research underlined that, besides the application rate, also the spray application equipment used has an important effect on the spray depositions. Nozzle type, size and pressure on the vertical spray boom system only had a minor effect on the spray deposition. Although the spray gun performed well on the easily accessible crop zone with the runners, its performance in the more dense main crop zone, was inferior. With 240% more sprayed liquid (8500 L•ha-1) and chemicals, the realized depositions in this crop zone were not significantly different from the ones obtained with the vertical spray boom system applying only 2500 L•ha-1. Spraying at 5000 L•ha-1, the vertical spray boom system achieved a 82.9% higher overall spray deposition in the main crop canopy zone compared with the spray gun at an application rate of 8500 L•ha-1. For the sprays applied with the vertical spray boom system, doubling the application rate resulted in equally higher spray depositions, except for the inner canopy deposition for which higher application rates were more effective.
Abstract: The quality of agricultural sprays plays an important role in the application of plant protection products. For 13 nozzle-pressure combinations, droplet size and velocity characteristics were measured 0.50 m below the nozzle using a PDPA laser-based measuring set-up. Nozzles were mounted on a transporter to sample the whole of the spray fan. The effect of nozzle type (standard, low-drift and air inclusion), nozzle size (ISO 02, 03, 04 and 06) and operating pressure (2.0, 3.0 and 4.0 bar) was tested.
Measured droplet sizes and velocities were related and both were affected by nozzle type, size and operating pressure. Droplet velocities at 0.50 m were determined by their size and initial ejection velocity. In general, bigger droplet sizes correspond with higher droplet velocities,and smaller droplets with lower droplet velocities. Important differences in velocities were observed depending on the nozzle type and size, both affecting the ejection velocity. For the same droplet size, droplet velocities were highest for the flat fan nozzles followed by the low-drift nozzles and the air-inclusion nozzles (because of the lower ejection velocities caused by pre-orifice and venturi effects). Similarly, the bigger the ISO nozzle size, the faster are the droplets of the same size
Droplet velocities of the larger droplet sizes (> 400 ïm) varied from about 4.5 up to 8.5 m s-1 depending on the nozzle type and size. Below 400 ïm, droplet velocities consistently decreased with the decrease of drop size, and vary from 0.5 to 2 m s-1 depending on the nozzle type and size.
All this information is very useful with regard to the risk of spray drift, crop penetration and the quantity and distribution of the deposit on the target.
Abstract: Germany, England, the Netherlands and Sweden have adopted measures to reduce the pollution of surface waters by spray drift in field crops and orchards. In 2004, Belgium also adopted a drift mitigation strategy. The Belgian legislation mainly consists of a classification list of spray nozzles; air assistance and shielded systems are also considered. The nozzle list firstly is an integration of the classification work of Germany, England and the Netherlands; it uses the most stringent of these three classifications. In this research, drift experiments examined whether the existing mitigation measures in field crops can be validated, and also whether the existing measures can be expanded with other techniques that are known to be drift-reducing but are not yet a part of the measures. The results were also compared with the legislations of other European countries. Spray drift was measured over grassland according to the international standard ISO/FDIS 22866. A Hardi Commander Twin Force field sprayer with boom length 27m, nozzle spacing 0.5m, and tank volume 32001 was used. Both conventional spraying and other spraying techniques were evaluated. Conventional spraying was defined as a spray boom with height 0.5 m, no downward air assistance, flat fan Hardi nozzles ISO 110 03, spray pressure 0.3 MPa, and forward driving speed of the tractor 8 kin h(-1). The other (non-reference) applications were varying nozzles (type and size), spray pressure, forward driving speed, boom height and applying downward air assistance. It was considered that the current Belgian measures can be improved and expanded. (C) 2007 Elsevier Ltd. All rights reserved.
Abstract: Despite the augmented safety offered by wearing a cyclist crash helmet, many cyclists still refuse to wear one because of the thermal discomfort that comes along with wearing it. In this paper, a method is described that quantifies the ventilation characteristics of a helmet using tracer gas experiments. A Data-Based Mechanistic model was applied to provide a physically meaningful description of the dominant internal dynamics of mass transfer in the imperfectly mixed fluid under the helmet. By using a physical mass balance, the local ventilation efficiency could be described by using a single input-single output system. Using this approach, ventilation efficiency ranging from 0.06 volume refreshments per second (s(-1)) at the side of the helmet to 0.22s(-1) at the rear ventilation opening were found on the investigated helmet. The zones at the side were poorly ventilated. The influence of the angle of inclination on ventilation efficiency was dependent on the position between head and helmet. General comfort of the helmet can be improved by increasing the ventilation efficiency of fresh air at the problem zones.
Abstract: In order to investigate and understand drift from field sprayers, a steady state computational fluid dynamics (CFD) model was developed. The model was developed in 3D in order to increase the understanding of the causes of drift: a deviation in the wind direction cannot be captured by a 2D approach, the wake behind a wind screen is not symmetrical, the effects of a changed nozzle orientation may not be symmetrical. The model's accuracy was validated with field experiments carried out according to the international standard ISO 22866. A field sprayer with a spray boom width of 27 in and 54 nozzles (Hardi ISO F1 10-03 at 3 bar) was driving at 2.22 m/s over a flat pasture. During the experiments the wind direction was perpendicular to the tractor track. The model explained the variation in drift replicates during each single field experiment through varying boom height (0.3-0.7 m), wind velocity (1.3-2.5 m/s), wind deviation (-18 degrees to + 18 degrees) from the direction perpendicular to the tractor track and injection velocity of the droplets (17-27 m/s). Boom movements had the highest impact on the variations in drift values (deviations in drift deposits of 25%), followed by variation in wind velocity (deviations in drift deposits of 3%) and injection velocity of the droplets (deviations in drift deposits of 2.5%). Wind deviation from the direction perpendicular to the tractor track had a reducing effect on the drift values (deviations in drift deposits of 2%). Small variations in driving speed had little influence on drift values. Near drift (< 5 m) is predicted well by the model but the increased complexity compromised the predictions at greater distances. The model will be further developed in order to improve far drift prediction. Dynamic simulations will be performed and the model for turbulent dispersion will be optimized. The model did not require calibration. (c) 2007 Elsevier B.V. All rights reserved.
Abstract: Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure the amount of sedimenting drift from a horizontal boom sprayer for different (drift reducing) spray application techniques under field conditions and to compare the results with the results from a reference spray, taking into account variations in meteorological conditions during the field drift experiments. Field drift measurements were performed for several combinations of nozzle type (standard flat-fan, low-drift, air inclusion) and size (ISO 02, 03, 04, and 06), spray pressure (2.0, 3. 0, and 4. 0 bar), driving speed (4, 6, 8, and 10 km h(-1)), and spray boom height (0.3, 0.5, and 0. 75 m) according to ISO 22866 by sampling in a defined downwind area at 24 different positions using horizontal drift collectors. The reference spray was defined as a standard horizontal spray boom without air support, a spray boom height of 0.50 m, a nozzle distance of 0.50 m, ISO 110 03 standard flat-fan nozzles at 3.0 bar (1.2 L min(-1)), and a driving speed of 8 km h(-1), resulting in an application rate of approximately 180 L ha(-1). Nozzle type as well as spray pressure, driving speed, and spray boom height, have an important effect on the amount of spray drift. Larger nozzle sizes, lower spray pressures and driving speeds, and lower spray boom heights generally reduce spray drift. Concerning nozzle types, air inclusion nozzles have the highest drift reduction potential, followed by the low-drift nozzles and the standard flat-fan nozzles. Drift results are closely linked with droplet size characteristics of the sprays.
Abstract: The characteristics of agricultural sprays belong to the most critical factors affecting spray drift, deposition on plants, spray coverage and biological efficacy. Hence, within the framework of a research project about agricultural spray drift, the effect of nozzle type, size and pressure on spray droplet characteristics was investigated. The objective of this study was to develop a test rig and protocol for the characterisation of spray nozzles using a phase doppler particle analyser (PDPA). This test rig was able to measure droplet sizes and velocities based on light-scattering principles. It was composed of a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA one-dimensional system. The droplet size and velocity characteristics of different nozzle-pressure combinations was measured and compared with the results obtained by other researchers using different measuring techniques and procedures. In total, 32 nozzle-pressure combinations were tested and classified based on droplet size spectra and the British Crop Protection Council (BCPC) classification scheme. The test results clearly show the effect of the nozzle type, size and pressure on the droplet size and velocity spectra. Comparison with the results from other researches confirms the need for reference nozzles to classify sprays because of the considerable variation of absolute results depending on settings and type of measuring equipment. (c) 2007 IAgrE. Published by Elsevier Ltd. All rights reserved.
Abstract: Characterising agricultural sprays is a critical factor when investigating and predicting the spray drift, deposition on plants, spray coverage and biological efficacy. Hence to underpin a research project to predict spray drift, a measuring protocol to enable consistent characterisation of spray from nozzles used in agriculture using a Phase Doppler Particle Analyser (PDPA) was developed. The set-up measures droplet sizes and velocities based on light-scattering principles. It comprises a controlled climate room, a spray unit, a three-dimensional automated positioning system, and an Aerometrics PDPA 1D system.
This paper presents a detailed description of the measuring set-up along with some experimental results. In total, 32 nozzle-pressure combinations were tested and spray quality categorized based on the British Crop Protection Council (BCPC) classification scheme using the measured droplet size spectra . The results confirmed the importance of nozzle type and flow rate on droplet size and their velocity The measurements will be used as an input for a Computational Fluid Dynamics drift-prediction model and to categorize nozzles based on their relative driftability.
Abstract: Proper delivery of pesticides into desired positions within crop canopies could result in a safe use of pesticides and reduce environmental pollution. A quantitative method with mineral chelates was used to evaluate spray deposits and distributions within tomato and pepper canopies. Tests were conducted in greenhouses with two different spray systems both equipped with vertical spray booms: a Fumimatic motor-driven sprayer and a manual-driven trolley sprayer. Deposition tests with water-sensitive paper and mainly with the manganese and molybdenum chelates as tracer elements were performed. Filter papers were placed at several heights within canopies to determine the spray distribution for changes in the vertical nozzle distance (0(.)35 versus 0(.)50 m) and the spray distance to the crop. The tests demonstrated that the spray with 0(.)35 m nozzle spacing provided a much better spray distribution than that with 0(.)50 m nozzle spacing. The optimal spray distance for 80degrees flat fan nozzles with the 0.35 m nozzle spacing was about 0(.)30 m. (C) 2004 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd.
Abstract: The European Crop Protection Association (ECPA) and the Agricultural Research Center (CLO-DVL) joined forces in a project to stimulate the safe use of pesticides in southern European countries. CLO-DVL optimized a method using mineral chelates as tracers on collectors. This quantitative method to evaluate spray deposits was used to compare operator exposure from several greenhouse spraying techniques. Operator exposure measurements were of a comparative nature. Five application methods were investigated: a standard spray gun with an operator walking forwards, a spray lance with an operator walking forwards and backwards, a trolley, and a vehicle, both with vertical spray booms. The exposure was measured with patches at 15 places on operators' coveralls and gloves, using mineral chelates as tracer elements. The difference in exposure of the patches between the different techniques was very high. Walking backwards reduced exposure by a factor of 7. The exposures with the trolley and the vehicle, two innovative spraying techniques, were respectively 25 and 100 times lower compared to exposure with the standard spray gun. Operator exposure while walking forward with the spray lance was about two times higher than with the spray gun. Besides very large differences in exposure among the five techniques, there were also large differences in exposure among various parts of the body. All of this is important in consideration of operator safety and for the parts of the body that need to be protected most.
Abstract: In the past decades agricultural productivity increased, but modern agriculture also became a threat to the environment and the safety of the produced food. To make regulations easy to understand and to apply they are expressed in general rules. However, today’s technology can determine and control every action applied to every single spot of farm land and every single farm animal. Therefore, extensive research on ICT and Robotics in agriculture and environmental (ICT-AGRI) related issues is conducted. The overall aim of this ICT-AGRI project is to strengthen and coordinate the European research, to develop a common European research agenda and to launch common calls. The specific objective of our work is to create central internet-based resources for researchers, developers and users within ICT and robotics in agriculture, and to stimulate coordination of research and development in this area through user-driven initiatives and activities. Therefore, a structured framework for mapping and analyzing all relevant knowledge within the described research area was developed.
Abstract: Application technology for biological insecticides like entomopathogenic nematodes (EPN) has been a relatively neglected area. One of the major considerations involved with the selection and use of an application system should be the application distribution pattern. While completely uniform distribution of the nematodes is not entirely essential to their success in soil applications, because there the nematodes can move short distances on their own, a uniform distribution is more important in foliar EPN applications. The present study examined the volumetric distribution pattern of Steinernema feltiae beneath a single standard flat fan, air induction, deflector and twinjet spray nozzle. A comparison with the distribution of a chemical tracer was made to reveal possible distribution problems. Droplet size spectra of the nozzles were measured and linked with the distribution results. A theoretical calculation of the coefficient of variation of the nematode distribution beneath a spray boom was performed. Finally, the actual spray pattern of the EPN on a horizontal surface beneath a spray boom was studied. We can conclude that the volumetric distribution pattern of EPN is influenced by nozzle type and is different from the volumetric distribution pattern of a chemical compound. By the spray overlap using a spray boom, differences in nematode distribution are however decreased to an acceptable level. Nozzle type significantly influences the number of nematodes deposited on a horizontal Petri dish and their distribution within the droplets. Future experiments are needed to reveal if the measured differences in coverage due to nozzle type will result in significant differences in pest control.
Abstract: Spray drift continues to be a major problem in applying agricultural pesticides. This paper summarizes the results of a 5 year study about drift from field crop sprayers using a unique integrated approach.
Indirect (spray quality and wind tunnel measurements) and direct drift experiments (field drift experiments) were performed and drift models were developed to study the effect of spray application technique, droplet characteristics, buffer zones, meteorological conditions, spray liquid properties, border structures and crop characteristics on drift from field crop sprayers. It was found that indirect drift measurements can be a valuable alternative to field drift experiments.
A validated 3-D Computational Fluid Dynamics (CFD) mechanistic drift model was developed which can be used for a systematical study of different influencing factors. This model was reduced to a fast 2-D diffusion advection model useful as a hands-on drift prediction tool.
From the experiments as well as from the models, the fraction of small droplets and the spray boom height were found to be the most influential spray application factors. Moreover, meteorological conditions as well as crop characteristics have an important effect on the amount of spray drift which can be reduced significantly using intercepting screens or buffer zones. From this study, drift protocols, data and models are made available which help to understand and reduce the complex phenomena of spray drift.
Abstract: Without an appropriate agitation system, sedimentation of entomopathogenic nematodes (EPN) in the spray tank can result in an unequal distribution over time. Therefore, agitation of the spray liquid containing EPN is very important. Moreover, nematodes are living organism who must remain viable during the application process. We assessed the effect of three agitation systems on the viability and the displacement of entomopathogenic nematodes in the spray tank. Mechanical, pneumatic and hydraulic agitation with a diaphragm pump during 120 min was not detrimental to Steinernema carpocapsae. Hydraulic agitation with a centrifugal pump during 120 min resulted in a decrease in viability of 80.7%. An additional experiment revealed that the temperature increase in the spray tank was the main source of the observed damage. No stable agitation could be preserved with the pneumatic agitation system. A significant loss in nematodes was observed at 0.15 m above the spray tank bottom after mechanical and hydraulic agitation. Future experiments should reveal the cause of nematode loss.
Abstract: Fewer plant protection products are now authorized for use than in the past. Frequent spraying with the same product or a suboptimal technique can lead to resistance in pests and diseases. Therefore, better application techniques could improve the sustainable use of the plant protection products still available.
This paper presents research results on the optimal use of spraying equipment and technology when growing ornamental crops. This project included a survey of Flemish ornamental growers, in which they reported using knapsack sprayers and lances for crop protection purposes.
Previous research has shown that boom systems may considerably improve crop protection management in greenhouses. The effectiveness of horizontal booms can be negatively affected by nozzle type and boom configuration. We studied the effect of nozzle type, spray pressure, boom height and spraying angle on the result of the spraying in ivy pot plants.
Abstract: Due to the decreasing availability of authorized plant protection products, adequate pest control becomes more difficult in many ornamentals. Although much attention is given to predator-pest interactions in integrated control, almost no research is available about the optimization of spray application techniques in ornamentals. Yet, spray boom systems - instead of the still predominantly used spray guns – might improve crop protection management in greenhouses considerably. Spray application technique will influence the spray deposition and as such its efficiency. In this study, the effect of air support and spray angle (-30°, 0°, 30°) on spray deposition in Ivy pot plants was tested using a coarse droplet spray nozzle (Lechler ID 90 02 at 6.0 bar). Spray deposition was measured using a quantitative method (mineral chelates).Spray coverage was assessed by the hand of a visual method using water sensitive paper. All applications were performed in the laboratory with a fully automated spray system. Spray deposits were measured at three plant levels on the top and on the bottom side of the leaves, together with off-target depositions. The use of air support improved crop penetration and deposition on the bottom side of the leaves and reduced spray deposition in the top layer at the top side of the leaves, resulting in a more uniform spray distribution over the crop canopy. The effect of air support on crop penetration was most pronounced with the standard 0° spray angle. Without air support, spray angling improved crop penetration but not the deposition at the bottom side of the leaves.
Abstract: Drift is of more concern for air-assisted orchard sprayers than for field sprayers due to the high air jet velocity involved and the horizontal application direction. Orchard sprays are applied sideways to the trees, with a high risk for aerial drift by wind. Air-assistance has also been shown to be non-uniform, but the consequences for deposition uniformity in the canopy have yet to be demonstrated. Off-target deposition can be minimized and uniformity can be improved with the use of proper equipment and methods under favourable weather conditions depending on the nature of the target canopy and the level of infection. To this end knowledge of the canopy flow conditions of both the air and the spray are needed. It has been difficult to obtain such information experimentally. A Computational Fluid Dynamics (CFD) model that allows the simulation of spraying process for different machines including environmental and canopy conditions is presented. This comprehensive model considers the effects of wind velocity and turbulence, and the nature of the canopy on air assistance distribution. Orchard experiments were conducted on airflow profile from three air assisted orchard sprayers in leafless and fully leafed pear tree (Pyrus communis L.) orchards. The model results compared well to the measured profiles of airflow distribution, with average accuracies as high as 80%. The model is used to study effects of sprayer and nozzle design and operational parameters, weather conditions, and for different planting systems and development stages.
Abstract: In 2007, 2008 and 2009, field trials were carried out with different standard and drift-reducing nozzles in sugar beet, maize, chicory, Belgian endive (all herbicide applications), wheat (fungicide application) and potatoes (haulm killing herbicide application). The effect of nozzle type (standard flat fan, low-drift flat fan, air injection), nozzle size (ISO 02, 03 and 04) and application volume on the biological efficacy was investigated. All applications were done using a plot sprayer with volume rates ranging from 160 to 320 l.ha-1 at recommended dose rates with range of commonly used plant protection products. For each crop, the experiments included four replicates in a randomized block design. Depending on the type of application, the efficacy was measured in terms of weed control, disease and yield level, percentage dead leaf and stem, etc. In a previous research, drift and droplet characteristics of the different techniques were measured.
In general no important effect of application technique on biological efficacy was observed for the tested herbicide and fungicide applications within the interval of volume rates and droplet sizes tested. Drift-reducing nozzles performed similar as conventional nozzles under good spraying conditions and using a correct spray application technique.
Abstract: In 2007 and 2008, field trials were carried out with different standard and drift-reducing nozzles in sugar beet, maize, chicory, Belgian endive (all herbicide applica-tions), wheat (fungicide application) and potatoes (Haulm killing herbicide application). The effect of nozzle type (standard flat fan, low-drift flat fan, air injection), nozzle size (ISO 02, 03 and 04) and application volume on the biological efficacy was investigated. All applications were done using a plot sprayer with volume rates ranging from 160 to 320 l.ha-1 at recommended dose rates with commonly used (mix of) plant protection products. For each crop, the experiments included four replicates in a randomized block design.
Depending on the type of application, the efficacy was measured in terms of weed control, disease and yield level, percentage dead leaf and stem, etc. In a previous re-search, drift and droplet characteristics of the different techniques were measured.
In general no important effect of application technique on biological efficacy was ob-served for the tested herbicide and fungicide applications within the interval of volume rates and droplet size tested. Drift-reducing nozzles performed similar as conventional nozzles under good spraying conditions and using a correct spray application tech-nique.
Abstract: Bay laurel is an evergreen, commercially grown and expensive ornamental pot plant, which is susceptible to different pests like aphids, scale and lerp insects, thrips, cat-erpillars of codling moth and sooty molds. Recently, caterpillars of the mediterranean carnation leafroller (Cacoecimorpha pronubana) cause more and more problems. These pests can lead to important financial losses for the growers.
During summer the individual pot plants are placed on a field-container in a fairly dense configuration. Crop protection is traditionally done by moving with a spray lance between the rows of pot plants and treating each individual plant from bottom to top. Good penetration is clearly an important advantages of this spray technique but it is very time-consuming, unhealthy and laborious. Some other growers use a ‘spray platform’ on a high-clearance tractor. Plants sprayed from this platform are exclusively approached from above resulting in an inferior spray deposition on the lower parts of the plants. To overcome the disadvantages of both available techniques, the potential of an automated tunnel sprayer was investigated.
Five different nozzle types were evaluated under laboratory conditions i.e. hollow cone, standard flat fan, air inclusion flat fan, deflector flat fan and twin air inclusion flat fan at spray pressures varying from 3.0 to 7.0 bar depending on the type of nozzle. For each nozzle type, three nozzle sizes were included in the experiments which resulted in 15 different spray application techniques. All experiments were done at a speed of 2.5 km.h-1. This resulted in three different application volumes: 2450, 4900 and 7300 l.ha-1.
After optimizing the nozzle configuration (distance and orientation) using water-sensitive paper, deposition tests with five different mineral chelates as tracer elements were performed. Filter papers were used as collectors at 20 different positions to measure spray deposition, distribution and penetration in the canopy. For each appli-cation technique, four plants were selected as repetitions.
Irrespective of the nozzle type and spray pressure, 4900 l.ha-1 was found to be the optimal spray volume with deposition rates varying from about 50 to 70% depending on the nozzle type. The best results were found for the hollow cone, the standard flat fan and the air inclusion flat fan nozzles. Nozzle type and pressure and the corre-sponding droplet characteristics were closely related with the penetration and deposi-tion results. With this automated tunnel system, it is possible to obtain a good spray result in combination with an increase in the productivity and a reduction in operator exposure.
Abstract: Increasingly, Flemish greenhouse growers use spray booms instead of spray guns to apply PPPs (Goossens et al., 2004). In spite of important advantages, e.g. a more uniform spray liquid distribution (Nuyttens et al., 2004) and a reduction in operator exposure (Nuyttens et al., 2009), many questions remain concerning their optimal settings (Braekman & Sonck, 2007).
The main objective of this research was to investigate the effect of spray application technique on the spray deposition in strawberries grown on beds in greenhouses and in particular the effect of nozzle type, size and spray pressure and the difference between the traditional spray gun and vertical spray booms (Braekman et al., 2009).
Abstract: Traditionally, Flemish growers of greenhouse crops predominantly use high pressure spray equipment. However, because of scaling up, companies want to automate labour-intensive activities, including crop spraying. Several experiments were performed to evaluate different spray application techniques (spray system and nozzle setting) in strawberries and ivy pot plants grown in greenhouses. In strawberries, using vertical spray booms at a moderate spray volume and with an appropriate nozzle choice led to an important improvement of the deposition rates, compared to the treatments with the spray lance. Trials in ivy pot plants showed that substantial savings on application rate and chemicals are possible when using vertical spray booms instead of the traditional spray gun, achieving higher deposition rates. In general, these experiments revealed that vertical spray boom equipment is a promising technique for applying plant protection products in a safe and efficient way in these crops.
Abstract: The withdrawal of approvals for agrochemicals on many food crops within Europe is likely to generate an increasing market for bio-pesticide products, including entomopathogenic nema-todes (EPN). However, for the EPN to be a success, a cost-effective and reliable usage should be assured. Therefore, progress in areas like application and formulation technology are needed, next to the development of optimal application strategies. A new research project will focus on optimizing the field application of EPN in vegetables. First, both application and formulation technologies will be optimized. Then, these technologies will be tested under semi-field conditions with special attention for the effect of weather conditions and timing of the application. All the acquired knowledge will be implemented and evaluated in field ex-periments. In this paper, the first results of the experiments on application technology are discussed.
Abstract: A whole series of field drift experiments were performed to investigate the effect of nozzle type (flat fan, low-drift, air inclusion) and size (ISO 02, 03, 04 and 06) on sedimenting spray drift. Sedimenting spray drift was determined by sampling in a downwind area at 24 different positions using horizontal drift collectors in combination with a fluorescent tracer with measurements up to 20 m from the directly sprayed zone. Meteorological conditions were continuously monitored. Based on 27 drift experiments with the reference spraying at various environmental conditions, the important effect of atmospheric conditions on the amount of near-field sedimenting spray drift was demonstrated and quantified. A non-linear drift prediction equation was set up and validated. This equation was used to compare the drift results of the different spraying techniques under various weather conditions with the reference spraying by calculating their total drift reduction potential (DRPt). Air inclusion nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles and the effect on drift deposits is high with DRPt values varying from -136.5 up to 89.8%. The effect of nozzle type is most important for smaller nozzle sizes A large database with (absolute) near-field drift results is made available to enlarge the international drift database with information about the effect of climatological conditions and spray application technology. The results are generally in good agreement with the results from different other studies although drift studies are difficult to compare due to differences in weather conditions, spray application techniques, methodologies and crop conditions.
Abstract: CropLife International and the Institute for Agricultural and Fisheries Research (ILVO-T&V-AT) joined forces in a project to stimulate the safe use of pesticides in Southern Europe. ILVO-T&V-AT optimised a method using mineral chelates as tracers on collectors. This quantitative method to evaluate spray deposits was used to compare operator exposure from several greenhouse spraying techniques.
Six application methods were investigated and compared i.e. a standard spray gun with an operator walking forwards, a spray lance walking forwards and backwards, a trolley, the Fumimatic and the Fumicar. The latter are novel spray application techniques with (vertical) spray booms. The exposure was measured at 15 different places on a coverall with patches and on gloves, using mineral chelates as tracer elements.
The difference in exposure of the patches between the different techniques was very high. Walking backwards reduced exposure by a factor 7. The total exposure on the collectors with the trolley, Fumicar and Fumimatic, was respectively 25, 7 and 100 times lower compared with the standard spray gun. Operator exposure walking forward with the spray lance was about two times higher than with the spray gun. Besides a very large difference in exposure between the five techniques, there was also a large difference in exposure between the various parts of the body. All of this is important in consideration of operator safety and for the parts of the body that need to be protected best.
Abstract: Three contrasting drift risk assessment means were evaluated when predicting absolute losses of sedimenting pesticide drift from field crop sprayers namely PDPA laser measurements, wind tunnel measurements (both indirect drift risk assessment means) and field drift experiments (direct drift risk assessment means). In total, 90 PDPA laser measurements, 45 wind tunnel experiments and 61 field drift experiments were performed with 10 different spray nozzles at a pressure of 3.0 bar. The effect of nozzle size (ISO 02, 03 04 and 06) and nozzle type (standard flat fan, low-drift flat fan, air inclusion) on the amount of near-field sedimenting spray drift was studied. The reference spray application was defined as a Hardi ISO F 110 03 standard flat fan nozzle at a pressure of 3.0 bar with a nozzle or boom height of 0.50 m and a driving speed of 8 km.h-1 for the field measurements; conditions that were always used for the comparative assessment of the different investigated nozzle-pressure combinations. In this paper, a comparison is made between the results obtained with the indirect drift assessment means and the direct drift assessment method to evaluate the potential of these three different drift assessment means. Results showed that with the indirect risk assessment means (wind tunnel and PDPA laser measurement), driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and both methods are suited to permit relative studies of drift risk. Moreover, based on these indirect drift measurements and a statistical drift prediction equation for the reference spraying, it is possible to come to a realistic estimate of field drift data at a driving speed of 8 km.h-1 and a boom height of 0.50 m
Abstract: Three contrasting drift risk assessment means were evaluated when predicting absolute losses of sedimenting pesticide drift from field crop sprayers namely PDPA laser measurements, wind tunnel measurements (both indirect drift risk assessment means) and field drift experiments (direct drift risk assessment means). In total, 90 PDPA laser measurements, 45 wind tunnel experiments and 61 field drift experiments were performed with 10 different spray nozzles at a pressure of 3.0 bar. The effect of nozzle size (ISO 02, 03 04 and 06) and nozzle type (standard flat fan, low-drift flat fan, air inclusion) on the amount of near-field sedimenting spray drift was studied. The reference spray application was defined as a Hardi ISO F 110 03 standard flat fan nozzle at a pressure of 3.0 bar with a nozzle or boom height of 0.50 m and a driving speed of 8 km.h(-1) for the field measurements; conditions that were always used for the comparative assessment of the different investigated nozzle-pressure combinations. A comparison is made between the results obtained with the indirect drift assessment means and the direct drift assessment method to evaluate the potential of these three different drift assessment means. Droplet size as well as droplet velocity characteristics are related with DRPt (field experiments) and DPRP (wind tunnel experiments). Because of the strong intercorrelation between droplet size and velocity characteristics for the nozzle-pressure combinations investigated in this study, simple first-order linear regressions with one of the droplet characteristics as a predictor variable, were the best choice to predict DRPt and DPRP. Results showed that with the indirect risk assessment means (wind tunnel and PDPA laser measurement), driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and both methods are suited to permit relative studies of drift risk. Moreover, based on these indirect drift measurements and a statistical drift prediction equation for the reference spraying, it is possible to come to a realistic estimate of field drift data at a driving speed of 8 km.h(-1) and a boom height of 0.50 m.
Abstract: The effect of several passages through a centrifugal pump on the viability and activity of Steinernema corpocapsoe was investigated. A tendency of reduced viability was detected after 10 passages through the centrifugal pump, but the difference was not statistically significant. Activity decreased significantly from 91.9% to 83.6%. The experimental set-up was chosen to eliminate temperature increase. Therefore, the results prove that mechanical pump damage cannot be excluded as the cause of EPN damage during spray application.
Abstract: This research investigated the drift-intercepting potential of structures surrounding the field borders, like artificial screens and crops, which are not yet a part of the drift mitigation measures for field crop sprayers in Belgium. Drift-interception experiments were performed in the wind tunnel of the International Centre for Eremology (Ghent University, Belgium) with various interception structures: Artificial screens with heights of 0.5, 0.75 and 1 m and screen open areas of 16, 36 and 63%; a row of plastic Christmas trees with heights of 0.5 and 0.75 m; and a potato canopy. The interception structure was positioned at 1 m from the field border. From the results it was found that type of border structure has a pronounced effect on the drift interception, while the height of the border structure had no significant effect.
Abstract: This research studied the effect of drift-intercepting structures surrounding the field borders, like artificial screens and natural hedges, which are not yet a part of the drift mitigation measures for field crop sprayers in Belgium. Drift-interception experiments were performed in a grassland (Lolium perenne) with various interception structures: Artificial screens with heights of 1, 1.5 and 2 m and screen open areas of 16, 36 and 63% and a row of Fagus sylvatica trees with a height of 1.5 m and an average leaf area index of 1.12 m2/m2. Experiments were performed according to the international standard ISO 22866. The interception structure was positioned at 1 m from the field border. From the results it was found that type of border structure as well as screen open area and screen height, have an important effect on the amount of spray drift. Highest drift reduction was found with a 1.5 m artificial screen with a 16% open area.
Abstract: Losses of pesticide active ingredients (a.i.) into the atmosphere can occur through several pathways. A main pathway is evaporation drift. The evaporation process of pesticide a.i., after application, is affected by three main factors: Physicochemical properties of the pesticide a.i., weather conditions and crop structure. The main physicochemical parameters are the Henry coefficient, which is a measure for the volatilization tendency of the pesticide a.i. from a dilute aqueous solution, and the vapour pressure, which is a measure for the volatilization tendency of the pesticide a.i. from the solid phase. Five pesticide a.i., with various Henry coefficients and various vapour pressures, were selected to conduct laboratory experiments: metalaxyl-m, dichlorovos, diazinon, Lindane and trifluralin. Evaporation experiments were conducted in a volatilization chamber. It was found that the evaporation tendencies significantly differed according to the physicochemical properties of the a.i.
Abstract: The spray quality generated by agricultural nozzles is important considering the efficiency of the pesticide application process because it affects spray deposits, biological efficacy and driftability. That is why a measuring set-up for the characterisation of spray nozzles was developed. This set-up is composed of a controlled climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA laser system which measures droplet size and velocity characteristics based on light scattering principles. Using this set-up and a well defined measuring protocol, droplet size and velocity characteristics of 15 different nozzle-pressure combinations were measured. It was found that at a nozzle distance of 0.50 m, droplet sizes vary from a few up to some hundreds of micrometres and droplet velocities from about 0 m.s(-1) up to 16 m.s(-1). From the results, the importance of the nozzle type and size on the droplet size and velocity spectra is clear. Standard flat fan nozzles produced the finest droplet size spectrum followed by low-drift and the air injection nozzles which results in significant differences in the proportion of small droplets. The larger the ISO nozzle size, the coarser is the droplet size spectrum and the lower is the proportion of small droplets. This effect is most pronounced for the standard flat fan followed by the low-drift nozzles and is less important for the air inclusion nozzles. Comparing the PDPA measuring results with other studies confirmed the need for reference nozzles to classify sprays because of the considerable variation of absolute results depending on variations in reference sprays, measuring protocol, measuring equipment and settings. As described in part 4, these results will be linked with the drift potential of different nozzle-pressure combinations.
Abstract: Wind tunnel measurements, performed in Silsoe Research Institute (SRI), were used to measure airborne and fallout spray volumes under directly comparable and repeatable conditions for single and static nozzles. Based on these measurements, drift potential reduction percentages (DPRP), expressing the percentage reduction of the drift potential compared with the reference spraying, were calculated following three approaches. The first approach was based on the calculation of the first moment of the airborne spray profile (DPRPv1). In the second and third approach, the surface under the measured airborne (DPRPv2) and fallout (DPRP(H)) deposit curve were used. These DPRP values express the percentage reduction of the drift potential compared with the reference spraying. Ten different spray nozzles were tested. The results showed the expected fallout profiles with the highest deposits closest to the nozzle and a systematic decrease with distance from the nozzle. For the airborne deposit profiles, the highest deposits were found at the Lowest collectors with an important systematic decrease with increasing heights. For the same nozzle size and spray pressure, DPRP values are generally higher for the air inclusion nozzles followed by the low-drift nozzles and the standard flat fan nozzles and the effect of nozzle type is most important for smaller nozzle sizes. In general, the bigger the ISO nozzle size, the higher the DPRP values. Comparing results from the three different approaches namely, DPRPv1, DPRPv2 and DPRP(H), some interesting conclusions can be drawn. For the standard flat fan nozzles, DPRPv1, values were the highest followed by DPRPv2 and DPRP(H) while for the low-drift nozzles opposite results were found. For the air inclusion nozzles, there was a relatively good agreement between DPRPv1, DPRPv1 and DPRP(H) values. All of this is important in the interpretation of wind tunnel data for different nozzle types and sampling methodologies.
Abstract: Pesticide spray drift is affected by 4 main factors: weather conditions, spray application technique, physicochemical properties of the spray Liquid and surrounding characteristics. This research studied the importance of crop type being sprayed for drift occurrence. Drift experiments were performed over cereals, cereal stubbles and grassland according to the international standard ISO 22866. From the results it was found that drift occurrence in cereals and cereal stubbles was lower than drift occurrence in grassland. The differences between cereals and cereal stubbles were significant only at low wind speed.
Abstract: Air assistance on field sprayers creates a forced airstream under the spray boom which blows the spray droplets into the crop. The advantages of this relative new technique are less drift of spray droplets and the possibility to reduce the amount of pesticides and spray Liquid. The purpose of this work was to investigate the effect of air assistance on the characteristics of spray droplets and their driftability. Based on air velocity measurements on an air assisted field sprayer, a system of air assistance was developed in addition to a laser-based measuring set-up for the characterisation of spray droplets. With this set-up, the effect of air support on the droplet characteristics was investigated for different settings of the air assistance. The effect on spray drift was quantified based on field drift measurements. A reducing effect on the total amount of spray drift was demonstrated for the Hardi ISO F 110 02, F 110 03 and LD 110 02 nozzles with drift reduction factors a(d) of, respectively, 2.08, 1.77 and 1.53. The use of air support had no significant effect for the LD 110 03 nozzles on the total amount of spray drift. Comparing droplet size and drift results, it was found that air support has the highest impact on the amount of spray drift for the finer sprays by increasing droplet velocities. The effect of air support on droplet sizes is rather limited.
Abstract: South European horticulture is still confronted with some problems in the field of greenhouse spraying applications. One of them is the operator’s safety because of the high operator exposure and the lack of protective clothing and equipment. The main objective of this study was to compare operator exposure for two different application methods: the traditional spray gun and the Fumicar.
There was a clear difference in total body contamination between both techniques. The Fumicar resulted in a 6.8 times lower total exposure compared with the spray gun walking forwards. Besides a difference in total exposure between both techniques, there was also an important difference in exposure between the various parts of the body. The operator exposure reduction using the Fumicar is the highest for the feet and the lower legs, followed by the arms and upper legs. For other parts of the body like the back, chest, head and hands, no reduction was found. All of this is important in connection with operator safety and for the parts of the body that need to be protected best when using a specific spray application technique.
Abstract: Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed (treated) area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure and compare the amount of drift for different climatological conditions under field conditions. Sedimenting spray drift was determined by sampling in a defined downwind area at different positions in a flat meadow using horizontal drift collectors for a reference spraying. Meteorological conditions were monitored during each experiment. A drift prediction equation for the reference spraying was set up to predict the expected magnitude of sedimenting drift at various drift distances and atmospheric conditions. The measurements proved the important effect of weather conditions (temperature, relative humidity and wind speed) on the amount of spray drift. A lower wind speed or a higher relative humidity decreases the amount of spray drift. Taking into account the correlation between temperature and relative humidity, a lower temperature will also result in lower drift values due to the cumulative effect of relative humidity. This equation can be used to quantify the effect of meteorological conditions, to compare measurements using other spraying techniques under different weather conditions to the reference spraying and to perform spray drift risk assessments.
Abstract: Characteristics of agricultural sprays belong to the most critical factors affecting spray drift, a major problem for the environment. That is why a measuring set-up for the characterisation of spray nozzles using a Phase Doppler Particle Analyser (PDPA) was developed which is able to measure droplet sizes and velocities based on light-scattering principles. It is composed of different parts i.e. a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA 1D system (Nuyttens et al., 2006 a). Different nozzle-pressure combinations have been tested. From the results, the importance of the nozzle type and size and the spray pressure on the droplet size and velocity spectra is clear.
These results are linked with the drift potential of the same nozzle pressure combinations based on field measurements for field sprayers carried out according to ISO 22866 by sampling in a defined downwind area at different positions in a flat meadow. Meteorological conditions (temperature, wind speed and direction, relative humidity, etc.) are monitored during each experiment. A reference spraying (with ISO 110 03 standard flat fan nozzles at 3 bar) was used since comparative measurements are to be made under different weather conditions. A drift prediction equation for this reference spraying was set up to predict the expected magnitude of sedimenting drift at various drift distances and atmospheric conditions (Nuyttens et al., 2006 b). This equation is used to compare measurements to the reference spraying using other nozzle types (flat fan, low-drift, air injection), sizes (ISO 02, 03, 04 and 06) and spray pressures (2, 3 and 4 bar).
Larger nozzle sizes and lower spray pressures generally reduce spray drift. Concerning nozzle types, air injection nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles. From these results, it is clear that spray drift and droplet characteristics are strongly linked.
Abstract: According to the Council Directive 91/414/EC pesticide damage should be assessed by considering the risk for persons arising from occupational, non-dietary exposure and risk to the environment. In this research an assessment for pesticide damage by droplet spray drift in grassland was set up. The percentages of droplet spray drift were estimated by field experiments in a meadow. A standard spraying was compared to some drift-reducing techniques. Knowing the percentages of drift and the applied doses of pesticide formulation in grassland, the human and environmental exposures (water and bottom) were predicted. Thereupon risk indices were calculated for water organisms, soil organisms and bystanders. A risk index is the ratio of a
predicted exposure to a toxicological reference value and gives an indication of the severity of the adverse effects likely to occur.
Abstract: In order to investigate and understand the high variability in field drift experiments a steady state CFD (Computational Fluid Dynamics) model was developed. The model is constructed in CFX 5.7 (Ansys CFX, Canonsburg, PA) and validated by experiments. The experiment took place in the summer of 2005 in Merelbeke (Belgium). A field sprayer with swath width of 27m and 54 nozzles (ISO F110-03@3bar) was driving cross wind over a pasture. The parameters of the model were set to match the experiment. There was an overprediction of drift by the model: 6% experimental drift vs. 21% modeled drift. The model did explain the variation in drift replicates during one experiment. Boom movements had the highest impact on the variations in drift values, followed by variation in wind velocity. Driving speed had little influence on fluctuating drift values. Driving direction however had a high reducing effect on the drift values.
Abstract: The characteristics of agricultural sprays belong to the most critical factors affecting spray drift, deposition on plants, spray coverage and biological efficacy. Hence, within the framework of a research project about agricultural spray drift, a measuring set-up for the characterisation of spray nozzles using a Phase Doppler Particle Analyser (PDPA) was developed. This set-up is able to measure droplet sizes and velocities based on light-scattering principles. It is composed of different parts i.e.: a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA 1D system.
In total, 32 nozzle-pressure combinations have been tested. From the results, the importance of the nozzle type and size on the droplet size and velocity spectra is clear. In future, the results will be linked with the drift potential of different nozzle pressure combinations (based on field measurements) and used as an input for a Computational Fluid Dynamics spray drift model.
Abstract: Recently, spray drift and its effects have become an important aspect of risk assessment in the registration process of pesticides in Belgium. In this regulation, drift reducing spray application techniques can be used to reduce buffer zones. The purpose of this research is to measure and compare the amount of drift sediment for different spray application techniques under field conditions. A drift prediction equation for the reference spraying was used to compare other spraying techniques with the reference spraying, under different weather conditions. Drift measurements were performed for several combinations of nozzle type (flat fan, low-drift, air injection) and size (ISO 02, 03, 04 and 06), spray pressure (2, 3 and 4 bar), driving speed (4, 6, 8 and 10 km.h-1) and spray boom height (0.3, 0.5 and 0.75 m). Nozzle type as well as spray pressure, driving speed and spray boom height, have an important effect on the amount of spray drift. Larger nozzle sizes, lower spray pressures and driving speeds and lower spray boom heights generally reduce spray drift. Concerning nozzle types, air injection nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles
Abstract: Droplet size distribution of a pesticide spray is recognised as a main factor affecting spray drift. As a first approximation, nozzles can be classified based on their droplet size spectrum. However, the risk of drift for a given droplet size distribution is also a function of spray structure, droplet velocities and entrained air conditions. Wind tunnel tests to determine actual drift potentials of the different nozzles have been proposed as a method of adding an indication of the risk of spray drift to the existing classification based on droplet size distributions (Miller et al, 1995). In this research wind tunnel tests were performed in the wind tunnel of the International Centre for Eremology (I.C.E.), Ghent University, to determine the drift potential of different types and sizes of nozzles at various spray pressures. Flat Fan (F) nozzles Hardi ISO 110 02, 110 03, 110 04, 110 06; Low-Drift (LD) nozzles Hardi ISO 110 02, 110 03, 110 04 and Injet Air Inclusion (AI) nozzles Hardi ISO 110 02, 110 03, 110 04 were tested at a spray pressures of 2, 3 and 4 bar. The droplet size spectra of the F and the LD nozzles were measured with a Malvern Mastersizer at spray pressures 2 bar, 3 bar and 4 bar. The Malvern spectra were used to calculate the Volume Median Diameters (VMD) of the sprays.
Abstract: The characteristics of agricultural sprays belong to the most critical factors affecting spray drift, deposition on plants, spray coverage and biological efficacy. Hence, within the framework of a research project about agricultural spray drift, a measuring set-up for the characterisation of spray nozzles using a Phase Doppler Particle Analyser (PDPA) was developed. This set-up is able to measure droplet sizes and velocities based on light-scattering principles. It is composed of different parts i.e.: a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA 1D system. This paper presents a detailed description of this measuring set-up along with some first measuring results. These measurements will be used as an input for a Computational Fluid Dynamics drift-prediction model and to classify nozzles based on their driftability.
Abstract: Drift, or the movement of pesticides away from the application target, is one of the major damaging side effects of pesticide spraying for the environment. The objective of this paper was the development nd validation of a Computational Fluid Dynamics (CFD) drift-prediction model for field spraying applications. This model will be able to predict drift for a wide range of variables and to present the results in a visual way for ease of interpretation.
The CFD model (CFX5.7, Ansys CFX, Canonsburg, PA) consisted of the 3D Reynolds-averaged Navier-Stokes equations for air flow with the k-ε model for turbulence coupled to a Lagrangian model for the spray droplet transport. The Lagrangian model accounted for particles inertia, drag and gravitational forces as well as turbulent dispersion. The droplets were injected at points according to the position of the nozzles and the specific nozzle features (flow rate, dropletparticle diameter distribution and velocity, and cone shape). The model was solved in a representative region of the atmospheric boundary
layer. The measured logarithmic wind profile perpendicular to the driving direction of the sprayer was implemented as a boundary condition. The field surface was a rough no-slip boundary. The other boundaries were openings with zero pressure condition. The model was solved in a moving coordinate system. The equations were solved by means of the finite volume method on an unstructured mesh of 675,000 tetrahedral elements. 24,000 droplet tracks were calculated for 6 nozzles. The simulations were performed on a P4 2.6GHz PC with 1Gb RAM, requiring 10,000 CPU seconds.
Validation of predicted off-target deposition patterns was performed by means of well-designed experiments in a flat meadow at the Agricultural Research Centre in Merelbeke, Belgium during the summer of 2004. The droplet diameter distribution and velocity (ISO 110 03 standard flat fan nozzle ,@ 3 bar) used in the model were obtained by PDPA laser experiments. Figure 1 visualizes the results of initial computations, presenting relative particle tracks for a wind speed of 3.5 m/s (at 5 m height) and a driving speed of 8 km/h. Note considerable drift of smaller particles across the field boundary (line on Figure 1). Figure 2 presents the downwind drift percentage values as a function of distance from the field boundary. The predicted values are within the experimentally observed range and show
similar decay, but are lower than average measured drift values. The model will be further developed to investigate more deeply evaporation, turbulent dispersion and the effect of solid objects (tractor, sprayer). In the next phase the model will be used to assess he effect of variations of conditions and parameters in a sensitivity study.
Abstract: Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed (treated) area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure and compare the amount of drift for different climatological conditions under field conditions. Spray drift was determined by sampling in a defined downwind area at different positions in a flat meadow using horizontal drift collectors (sedimenting spray drift) and pipe cleaners (airborne spray drift) for a reference spraying. Meteorological conditions were monitored during each experiment. A drift prediction equation for the reference spraying was set up to predict the expected magnitude of sedimenting drift at various drift distances and atmospheric conditions (wind speed and temperature). This equation can be used to compare measurements using other spraying techniques under different weather conditions to the reference spraying. In 2005, more measurements will be performed to validate the statements and the model reflected in this paper.
Abstract: Most studies on uniformity of pesticide applications beneath agricultural spraying booms are based on the characteristics of nozzle spray patterns. When optimising general features (boom height, pressure, ...), average nozzle characteristics are used. In this research, individual nozzle characteristics are essential. When utilising slightly used nozzles, small irregularities in the nozzle spray distribution may be averaged out or amplified in the resulting full-boom distribution. A method is proposed to find whether the coefficient of variation (cv) of a field sprayer spray distribution could be optimised by altering the sequence and orientation of a given set of flat fan nozzles. A manageable model is used in order to quickly compute possible full-boom distributions (and cv's) with a given set of single nozzle spray distributions. The individual nozzle spray distributions are extracted from a limited series of full-boom spray distribution measurements (three in most cases) with randomised nozzle sequence and orientation by means of a Matlab optimisation algorithm.
Abstract: Spray drift is defined as the quantity of applied product –representing an active ingredient of a pesticide- which is deflected from the treated area by the action of air currents during the application process. The deposition of pesticides outside the target field can have negative effects on the health of humans and animals, and can also damage sensitive adjoining crops.
The purpose of this research was to assess spray drift damage for ten major crops in Flanders, Belgium.
Abstract: The characteristics of agricultural sprays belong to the most critical factors affecting spray drift, deposition on plants, spray coverage and biological efficacy. Hence, within the framework of a research project about agricultural spray drift, a measuring set-up for the characterisation of spray nozzles using a Phase Doppler Particle Analyser (PDPA) was developed. This set-up is able to measure droplet sizes and velocities based on light-scattering principles. It is composed of different parts i.e.: a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA 1D system.
This paper presents a detailed description of this measuring set-up along with some first measuring results. These measurements will be used as an input for a Computational Fluid Dynamics drift-prediction model and to classify nozzles based on their driftability
Abstract: Southern European horticulture is still confronted with many problems in the field of greenhouse spraying applications. One of them is operator safety because of the high operator exposure and the lack of protective clothing and equipment.
That is why the European Crop Protection Association (ECPA) and the Agricultural Research Centre (CLO-DVL) joined forces in a project to stimulate the safe use of pesticides in southern European countries. The subproject presented in this article deals with both new and traditional spraying equipment for the application of crop protection products in greenhouses in southern Europe. The main objective was to compare operator exposure for five different application methods.
CLO-DVL optimized a method using mineral chelates as tracers on collectors. This quantitative method to evaluate spray deposits was used to compare operator exposure from several greenhouse spraying techniques. Operator exposure measurements were of a comparative nature and were performed under field conditions in two greenhouses for pepper. Five application methods were investigated each by four different experienced operators: a standard spray gun with an operator walking forwards, a spray lance with an operator walking forwards and backwards, a trolley, and a vehicle, both with vertical spray booms. A different chelate was used for each application method (Mn, Co, Mo, Zn, and B). The exposure was measured with patches (10 x 10 cm²) at 15 places on the operators' coveralls and gloves, using mineral chelates as tracer elements. The difference in exposure of the patches between the different techniques was very high. Walking backwards reduced the exposure by a factor of 7. The exposures with the trolley and the vehicle, two innovative spraying techniques, were respectively 25 and 100 times lower compared to the exposure with the standard spray gun. Operator exposure while walking forward with the spray lance was about two times higher than with the spray gun. Besides very large differences in exposure among the five techniques, there were also large differences in exposure among various parts of the body. With the spray lance and the spray gun, the highest exposures were measured on the legs and feet. The lower the position on the body, the higher the exposure was. There was also a high exposure on the hands, the forearms, and the head. With the manually pulled trolley and the Fumimatic, the exposure was highest for the hands. All of this is important in consideration of operator safety and for the parts of the body that need to be protected most.
Abstract: In the history of pesticide drift-measuring techniques, different tracers and collection techniques have been used.
At the start of a new Flemish IWT project ‘Protecting the Flemish environment against drift - The importance of drift-reducing techniques’, wind tunnel tests have been performed to select the most efficient tracer and collection technique. The most important objective of this study was to investigate the effect of a certain combination of collection and tracer techniques on the measured drift quantities.
As tracer types a fluorescent tracer (Renaissance W15), two different mineral chelates (cobalt and molybdenum), a NaCl-solution and a fungicide (Tolylfluanide) were used. Two different collection techniques were tested: ditches incorporated in the wind tunnel floor with filter paper and with filtering cloths. The recovery of the different tracers combined with the two collection materials was calculated.
The advantages and disadvantages of the tracers and collection materials are enumerated in this article.
Abstract: According to the Council Directive 91/414/EC pesticide damage should be assessed by considering the risk for persons arising from occupational, non-dietary exposure and risk to the environment. In this research an assessment for the pesticide damage by droplet spray drift was set up. The percentages of spray drift were estimated with the Ganzelmeier drift curves and the IMAG drift calculator. Knowing the percentages of drift and the applied doses of pesticide formulations in a given crop, the human and environmental exposures (water and bottom) were predicted. Thereupon risk indices were calculated for water organisms, soil organisms and bystanders. A risk index is the ratio of a predicted exposure to a toxicological reference value and gives an indication of the incidence and the severity of the adverse effects likely to occur. Considering the risk index it is possible to define the minimal width of an unsprayed field margin or "buffer zone" to reduce this risk at an acceptable level.
Abstract: The European Crop Protection Association and CLO-DVL joined forces in a project to compare operator exposure from several greenhouse spraying techniques. Five application methods were investigated. A standard spray gun with an operator walking forwards, a spray lance with an operator walking forwards and backwards and a trolley and a vehicle both with vertical spray booms. The exposure was measured at 15 different places on the body with patches and on gloves, using mineral chelates as tracer elements. The difference in exposure between the different techniques was very high. Walking backwards reduced the exposure by a factor of 7. The exposure on the collectors with the trolley and the vehicle was respectively 25 and 100 times lower compared with the standard spray gun. Besides a very large difference in exposure between the five techniques, there was also a large difference in exposure between the various parts of the body. All of this is important in consideration of operator safety and for the parts of the body that need to be protected best.
Abstract: CLO-DVL have optimised a method using mineral chelates for quantitative evaluation of spray deposits. This method was used to assess spray distributions with two novel spraying techniques. Deposition tests were performed with a manually pulled trolley and a motorised vehicle both equipped with vertical spray booms, with water-sensitive paper and mainly with the manganese and molybdenum chelates as tracers. Filter papers were attached to the tomato and pepper plants at several heights to obtain an indication of the spray distribution in the crop. Particular attention was paid to the effect on the spray distribution of the vertical nozzle distance (35 cm vs 50 cm) and the spray distance to the crop. The tests demonstrated that a nozzle spacing of 35 cm delivers a much better spray distribution than one of 50 cm. The optimal spray distance for flat fan nozzles with a spray angle of 80° and a nozzle spacing of 35 cm is about 30 cm.
Abstract: Over the last decade, drift of pesticides caused by spraying has been recognised as a major problem for the environment. Especially for the specific situation in Flanders, there is still a lack of information concerning this topic. That is why the Agricultural Research Centre and the Universities of Leuven and Ghent joined forces in a new project: ‘Protecting the Flemish environment against drift – The importance of drift-reducing techniques’. This project just started in September 2003. Hence, at the moment of writing this paper, no practical results are available. The main objectives of this project are: 1. Obtaining an in-depth scientific insight into drift (vapour and droplet), related to the formulation and spraying technique for boom sprayers for Flemish conditions (soil, climate, small landscape elements, environmental planning, etc.). 2. Developing an application method for the users of plant protection products to apply these products as economically and ecologically as possible. 3. Developing a spray drift model using Computational Fluid Dynamics (CFD) and a scenario for the evaluation of new products and drift-reducing techniques.
This paper describes briefly the objectives and the proposed materials and methods of this research project funded by the Ministry of the Flemish Community.
Abstract: In the history of pesticide drift measuring techniques, different tracers and a lot of different collection techniques have been used. At the start of a new Flemish project 'Protecting the Flemish environment against drift - The importance of drift-reducing techniques', wind tunnel tests have been executed to select the most efficient tracer and collection technique. As tracer types a fluorescent tracer Renaissance W15, 2 different chelates, a NaCl-solution and a fungicide Tolylfluanide were used. 2 different collection techniques were tested: drains incorporated in the wind tunnel floor filled with filter paper and filled with cloths. The recovery of the different tracers combined with the 2 collection materials was calculated. The advantages and disadvantages of the tracers and collection materials are enumerated in this article.
Abstract: The European Crop Protection Association (ECPA) and CLO-DVL joined forces in a project to stimulate a safe use of pesticides in Southern European countries. A quantitative method to evaluate spray deposits, using mineral chelates, is used to compare operator exposure from several spraying techniques. The operator exposure measurements were of a comparative nature. Five application methods were investigated, i.e. a standard spray gun with an operator walking forwards, a spray lance with an operator walking forwards and backwards, a trolley and a vehicle both with vertical spray booms. The exposure was measured at 15 different places of the body on a coverall with patches and on gloves. Walking backwards reduced the exposure by a factor of 7. The exposures on the collectors with the trolley and the vehicle, were factors of 25 and 100 lower respectively than with the standard spray gun. Besides a very large difference in exposure between the five techniques, there was also a large difference in exposure between the various parts of the body. This data is important in consideration of operator safety and for the parts of the body that need to be protected most.
Abstract: The European Crop Protection Association (ECPA) and CLO-DVL joined forces in a project to stimulate a safe use of pesticides in Southern European countries. CLO-DVL optimised a method with mineral chelates to evaluate deposition tests. This quantitative method to evaluate spray deposits and to check spray distributions is used to assess two novel spraying techniques. Deposition tests with water-sensitive paper and mainly with the manganese and molybdenum chelates as tracer elements were performed with a manually pulled trolley and a motorised vehicle both equipped with vertical spray booms. Filter papers were attached to the tomato and pepper plants at several heights to obtain an indication of the spray distribution in the crop. Particular attention was paid to the effect on the spray distribution of the vertical nozzle distance (35 cm vs. 50 cm) and the spray distance to the crop. The tests proved that a nozzle spacing of 35 cm delivers a much better spray distribution than one of 50 cm. The optimal spray distance for flat fan nozzles with a spray angle of 80 degrees and a nozzle spacing of 35 cm is about 30 cm.
Abstract: Society’s preoccupation with the use of plant protection products has increased significantly during the last few years. When pesticides are applied some of the spray may move beyond the intended area to undesirable areas which might have consequences such as damage to sensitive adjoining crops, water contamination, health risks to animals and people and a lower dose than intended on the target field.
The general objective of this research was to investigate the influence of spray application technology on the amount of spray drift from field crop sprayers. Therefore, indirect and direct drift assessment means were used and compared namely PDPA laser, wind tunnel and field drift measurements. A reference spraying was used for a comparative assessment of the different evaluated spray application techniques. This reference spraying was defined as a standard horizontal boom sprayer with a spray boom height and nozzle distance of 0.50 m, ISO 03 standard flat fan nozzles at a pressure of 3.0 bar and a driving speed of 8 km.h-1. Besides this reference spraying, different other spray application techniques were tested to assess the effect of nozzle type (standard flat fan, low-drift, air inclusion), nozzle size (ISO 02, 03, 04 and 06), spray pressure (2.0, 3.0 and 4.0 bar), driving speed (4, 6, 8 and 10 km.h-1), spray boom height (0.30, 0.50 and 0.75 m) and air assistance.
The developed PDPA laser measuring set-up is composed of a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA laser system in a controlled climate room which measures droplet size and velocity characteristics using a well-defined measuring protocol.
Wind tunnel measurements, performed in Silsoe Research Institute (SRI), were used to measure airborne and fallout spray volumes under directly comparable and repeatable conditions for single and static nozzles. Based on these measurements, drift potential reduction percentages (DPRP), expressing the percentage reduction of the drift potential compared with the reference spraying, were calculated following three approaches. The first approach was based on the calculation of the first moment of the airborne spray profile (DPRPV1). In the second and third approach, the surface under the measured airborne (DPRPV2) and fallout (DPRPH) deposit curve were used.
For the field measurements, sedimenting spray drift was determined by sampling in a downwind area at 24 different positions using horizontal drift collectors in combination with a fluorescent tracer with measurements up to 20 m from the directly sprayed zone. Meteorological conditions were continuously monitored.
Based on 27 drift experiments with the reference spraying at various environmental conditions the important effect of atmospheric conditions on the amount of near-field sedimenting spray drift was demonstrated and quantified. A non-linear drift prediction equation was set up and validated, to predict the expected magnitude of drift for the reference spray application as a function of drift distance, average wind speed at a height of 3.25 m, average temperature and absolute humidity. This equation shows that decreasing wind speed and temperature and increasing absolute humidity decreases the amount of sedimenting spray drift and stresses the important effect of air humidity and temperature. This equation was used to compare the drift results of the different spraying techniques under various weather conditions with the reference spraying by calculating their drift reduction potential (DRPt).
In total, 162 PDPA laser measurements, 51 wind tunnel experiments and 108 field drift experiments were performed. From these measurements, droplet size and velocity characteristics at a nozzle distance of 0.50 m, drift potential reduction percentages (DPRPV1, DPRPV2 and DPRPH) and drift reduction potentials (DRPt) were determined and compared for the different spray application techniques to investigate their effect on the amount of near-field sedimenting spray drift and to evaluate the potential of the different drift assessment means.
From the PDPA measurements, it was found that droplet sizes vary from a few up to some hundreds of micrometres and droplet velocities from about 0 m.s-1 up to 16 m.s-1. Droplet sizes and velocities are related and both are influenced by nozzle type, size and spray pressure. Droplet velocities at 0.50 m are mainly determined by the ejection velocity and by their size. Smaller droplets slow down more rapidly due to the effect of air drag compared to larger droplets. Although bigger droplet sizes generally correspond with higher droplet velocities (and vice versa) droplet velocities for one and the same droplet size range vary depending on nozzle type and size because of variations in ejection velocities. The PDPA measuring set-up was capable of producing huge amounts of useful and repeatable droplet velocity and size information under controlled conditions. Comparing the PDPA measuring results with other studies confirmed the need for reference nozzles to classify sprays because of the considerable variation of absolute results depending on measuring protocol, settings, type and variations in reference sprays and measuring equipment.
Standard flat fan nozzles produced the finest droplet size spectrum followed by low-drift and the air injection nozzles which results in significant differences in the proportion of small droplets (e.g. V100, V200) and different other droplet size characteristics like Dv0.5, RSF, D10, etc. The effect of nozzle type on droplet sizes was more important for the smaller ISO nozzle sizes. For the same droplet size, velocities are the highest for the flat fan nozzles followed by the low-drift and the air inclusion nozzles which is caused by differences in ejection velocities resulting from the pre-orifice effect in case of a low-drift nozzle and by a combination of venturi and pre-orifice effect for the air inclusion nozzles. In spite of this, droplet velocities are generally highest for the air inclusion nozzles, followed by the low-drift and the standard flat fan nozzles - for the same ISO nozzle size and spray pressure - because of their coarser droplets corresponding with higher velocities. Hence, the droplet size effect dominates the ejection velocity effect. From the wind tunnel and field experiments, highest DRPt and DPRP values are found for the air inclusion nozzles followed by the low-drift and the standard flat fan nozzles. Again, the effect of nozzle type is most important for the smaller nozzle sizes.
The larger the ISO nozzle size, the coarser is the droplet size spectrum and the lower is the proportion of small droplets. This effect is most pronounced for the standard flat fan followed by the low-drift nozzles and is less important for the air inclusion nozzles. Bigger ISO nozzle sizes also correspond with higher droplet velocities for the same nozzle type and spray pressure. This is caused by two factors which strengthen each other namely, bigger ISO nozzles produce bigger droplets which are faster and droplets of the same size produced by bigger nozzles are faster because of higher ejection velocities. These effects of nozzle size on droplet characteristics are clearly reflected in the results from the wind tunnel and the field measurements. The bigger the ISO nozzle size, the higher the DPRP and DRPt values for the standard and the low-drift flat fan nozzles. For the air inclusion nozzles, the effect of nozzle size on DPRP and DRPt values is less clear but in all cases, DPRP and DRPt values are high and the highest values are found for the ISO 03 nozzles.
To investigate the effect of spray pressure, a series of measurements was carried out with the ISO 03 standard flat fan nozzle within a pressure range from 2.0 to 4.0 bar. For the droplet velocities, only the fastest droplet velocity characteristics (vvol75 and vvol90), significantly decrease with decreasing pressures. Although decreasing pressure from 3.0 to 2.0 bar did not significantly affect droplet size characteristics, fallout and airborne downwind spray deposits in the wind tunnel significantly increased because of this slight reduction in droplet velocities in combination with a decrease in entrained air velocities. On the other hand, this decrease in spray pressure resulted in a clear decrease in the amounts of field drift which was in contrast with the results from the wind tunnel and the PDPA laser measurements. Increasing the spray pressure from 3.0 to 4.0 bar significantly decreased droplet sizes but the effect was limited compared to the effect of nozzle size. In the field, an increase in spray drift was found.
Besides nozzle type, size and spray pressure, all having an effect on spray quality, driving speed and boom height also influence the amount of spray drift. Based on the field and the wind tunnel experiments, it was found that operating at a boom height as close as possible to the vegetation - without sacrificing the spray pattern - is a good way to reduce drift. The effect of driving speed could only be investigated in a realistic way in the field. A decrease in spray drift is observed for lower driving speeds of 4 and 6 km.h-1 while the difference between the reference speed of 8 km.h-1 and a speed of 10 km.h-1 is statistically non-significant.
Looking at the effect of air assistance, a reducing effect on the total amount of spray drift is demonstrated for the Hardi ISO F 110 02, F 110 03 and LD 110 02 nozzles with drift reduction factors αd of, respectively, 2.08, 1.77 and 1.53. No significant effect was found for the LD 110 03 nozzles which demonstrates that the finer the spray, the higher the impact of air assistance is on the amount of spray drift.
Comparing the results of the three drift assessment means, droplet size as well as velocity characteristics are related with field measurement DRPt values and wind tunnel DPRP values. In general, DRPt and DPRP values increase with increasing values of droplet diameter and velocity characteristics and decrease with increasing percentages of small droplets.
The proportion of the total volume of droplets smaller than 200 μm (V200), was found to be the best individual indicator for the amount of sedimenting spray drift with an R² of 0.90. Besides V200, the droplet size characteristics V50, V75, V100, V150 and V250 and the velocity span factor (VSF) were also strongly related with DRPt. The higher the VSF value, representing a less uniform droplet velocity distribution, the lower the DRPt value which can be explained by the clear relation between droplet sizes and velocities which is reflected in the VSF values.
With regard to the wind tunnel measurements, the different individual droplet size characteristics are best related with DPRPH followed by DPRPV2 and DPRPV1, the opposite is found for the droplet velocity characteristics. With regard to DPRPH, V100, V150 and V200 have the highest predictive power (R² = 0.92), while DPRPV1 was related most with vvol10 (R² = 0.86) and DPRPV2 with VSF (R² = 0.90) which shows again that droplet sizes and velocities are linked and that droplet size characteristics are more related with fallout compared to airborne deposits while the opposite is found for the droplet velocity characteristics.
A fairly good correlation was found between field drift DRPt and wind tunnel DPRP values with the best agreement with DPRPH (R² = 0.88) followed by DPRPV2 (R² =0.81) and DPRPV1 (R² = 0.66). Moreover, similar trends are found – concerning the effect of nozzle type, size, height and pressure - from the DPRP and DRPt results although there are some deviations in absolute results mainly for a varying spray pressure and nozzle height. This means on the one hand that the wind tunnel approach calculating the surface under the fallout deposit curve, is best suited to represent real near-field sedimenting drift characteristics. On the other hand it indicates that the indirect drift assessment method measuring V200 values is at least as well suited to represent near-field drift characteristics compared with the wind tunnel approach calculating DPRPH and even better suited compared with the wind tunnel approaches calculating DPRPV1 and DPRPV2. With the PDPA laser, it is only possible to investigate the effect of nozzle type, size and spray pressure whereas the effect of nozzle height can also be investigated by means of wind tunnel measurements. With both indirect techniques, it is difficult to investigate effects like driving speed and air assistance where direct drift measurements are necessary. Field research is appropriate for obtaining realistic estimates of drift under a range of working conditions but it is time-consuming and expensive. In this study, a measuring protocol and a drift prediction equation were set up to improve the interpretation of field drift data. With this equation and DRPt of a certain spray application technique, realistic sedimenting field drift data for varying meteorological conditions can be calculated. With the indirect drift assessment means, driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and both methods are suited to permit relative studies of drift risk. Moreover, based on DPRPH or V200 - resulting from wind tunnel and the PDPA measurements - the DRPt of a certain technique can be determined to come to a realistic estimate of field drift data at a driving speed of 8 km.h-1 and a boom height of 0.50 m. This information is useful for all users of plant protection products, constructors and authorities for decision-making and risk assessment processes.
With this study, a large database with droplet characteristics, wind tunnel fallout and airborne deposits and (absolute) near-field drift results of different spray application techniques is made available together with information about the effects of climatological conditions. The results of this research are in fairly good agreement with the results from different other studies although it is difficult to compare because of differences in, among others, spray application techniques, experimental design, tracers and weather and crop conditions. That is why it is increasingly important to unify the different indirect and direct drift assessment means and to put together the different available databases.
