Spray Losses Research Articles

Atmospheric loss of pesticides above an artificial vineyard during air-assisted spraying

A procedure to assess pesticide emission to the air and characterise possible air pollution sources was carried out using a tracer dye and 2 mm PVC lines during air-assisted spraying of an artificial vineyard. Three experiments were performed to evaluate the method feasibility, quantify upward movements of sprayed droplets and investigate the influence of microclimatic variables on pesticide emission. During each experiment two test series were carried out with two droplet size distributions (very fine and fine spray, according to the BCPC classification). The amount of sprayed liquid collected at 2.5 m above ground varied between 9.0% and 10.7% of the total dose applied for very fine spray and between 5.6% and 7.3% for fine spray. In stable atmospheric conditions the spray drifted along the mean wind direction over the crop whereas in unstable conditions the sprayed liquid plume was larger, with a greater amount of material sent to higher levels. A statistical model based on a simple multiple regression featuring droplet characteristics and microclimatic variables (wind speed, temperature, stability parameter and relative humidity) provided a robust estimate of spray loss just above the crop, with an acceptable determination coefficient ( R 2=0.84). This method is therefore suitable for quantifying spray drift and provides a way to study the influence of several variables on the amount of pesticide released into the atmosphere by air-assisted spraying, with suitable accuracy.

Spray deposition and losses in potato as a function of air-assistance and sprayer boom angle

Within the Brazilian agricultural scene, the potato crop plays a significant economic role. Modern equipment and the development of improved chemical product application techniques contribute toward the constant search for improved revenue from the potato as a crop. Field experiments were carried out in a random block design of a potato crop of the "Ágata" variety. The aim was to evaluate the effect of air assistance combined to different angles of spray application on the chemical deposition on the potato plant, as well as to assess spray losses to the soil. For this a sprayer with and without boom air assistance was used in the experiments. Boom angles of 0º, +30º and -30º were directed to a vertical position as well as forward and backward movements. The trial plants were sprayed at a volume rate of 400 L ha-1 using JA-4 hollow cone nozzles at 633 kPa and copper oxychloride as a tracer for the deposit evaluation. Trace deposits on both surfaces of leaflets were removed by washing with destilled water and were quantified by atomic absorption spectrophotometry. Spray losses were measured by placing plastic measuring collectors between rows. The deposit levels at different positions in the plant were analyzed by the Hotelling T² statistical test. Larger deposits were detected at both upper and lower positions of the plant when the spray boom was positioned at 0º and +30º in the presence of air assistance. The presence of air, in addition to the increasing spray deposits in the lower parts of the plant, helped to create greater distribution uniformity. Spray loss was below 4%.

Static and dynamic distribution of spray from single nozzles and the influence on biological efficacy of band applications of herbicides

Spray distributions from different stationary nozzles were measured when adjusted to apply 20, 15 and 10 cm bands. As the distribution is influenced by the prevailing wind conditions and driving speed, the dynamic spray distribution of some of these nozzles was also measured. Spray losses were calculated as deviations from the optimal even-spray volume distribution in the band. The best distribution for band application was obtained using even-spray nozzles, whereas standard flat-fan nozzles and hollow-cone nozzles had an uneven distribution with a peak just below the nozzle centre and less spray towards the edges of the spray swath. In field experiments applying phenmedipham against Brassica napus as a model weed, the biological efficacy of the nozzles using the same bandwidth settings was compared with broadcast applications. There was a poor correlation between the measured spray distribution in the static test and biological efficacy in the field, which declined when the bandwidth was reduced to less than 20 cm. Reasons for this are discussed.

Validation of fluid bed granulation utilizing artificial neural network

Three innovative components (an annular gap spray system, a booster bottom and an outlet filter) have been developed by Innojet Technologies to improve fluid bed technology and to reduce the common interference factors (clogging of nozzles and outlet filters, spray loss, spray drying and fluidized bed heterogeneity). In a fluid bed granulator, three conventional components have been replaced with these innovative components. Validation of the modified fluid bed granulator has been conducted using a generalized regression neural network (GRNN). Under different operating conditions (by variation of inlet air temperature, liquid-binder spray rate, atomizing air pressure, air velocity, amount and concentration of binder solution and batch size), sucrose was granulated and the properties of size, size distribution, flow rate, repose angle and bulk and tapped volumes of granules were measured. To confirm the method's validity, the trained network has been used to predict new granulation parameters as well as granule properties. These forecasts were then compared with the corresponding experimental results. Good correlation has been obtained between the predicted and the experimental data. From these findings, we conclude that the GRNN may serve as a reliable method to validate the modified fluid bed apparatus.

A SYSTEM TO ASSESS THE MASS BALANCE OF SPRAY APPLIED TO TREE CROPS

The measurement of pesticide spray losses from air blast sprayers as they apply to tree crops is required to providethe industry with information on sprayer efficiency. Spray loss, however, is often difficult to measure using currentstandardized methods. Test procedures are often time consuming and too costly to be extensively used. To facilitate samplingof spray losses during application to tree crops, a device consisting of an adjustable metal frame and a grid has beendeveloped. The grid supports artificial targets. The frame stands in the vineyard or orchard over two adjacent rows, allowingthe sprayer to pass below the structure, while applying a predetermined spray volume rate. Spray deposit on the collectorsenables assessment of the amount of spray droplets dispersed in the atmosphere around the plant target. On one hand, thesystem aims to develop an alternative procedure to the presently proposed ISO methodology (DIS 22369.2) for classificationof orchard/vineyard sprayers according to drift risk. On the other hand, it could facilitate the study of the spray mass balancedischarged to target plants, ground, and atmosphere, integrating ISO standard CD 22522 concerning field measurement ofspray distribution in tree and bush crops. This article reports the first experimental results related to the use of the device.

Deposição e perdas da calda em feijoeiro em aplicação com assistência de ar na barra pulverizadora

Com o objetivo de avaliar a influência da assistência de ar na deposição da calda de pulverização, em plantas de feijoeiro (Phaseolus vulgaris) aos 26 dias após a emergência (DAE), com pontas de pulverização de jato cônico vazio (JA-0,5 e JA-1) e jato plano (AXI-110015), e volumes de calda, foi realizado um experimento em delineamento inteiramente casualizado, utilizando como traçador o íon cobre. Alvos coletores (papel de filtro com 3 x 3 cm) foram afixados nas superfícies adaxial e abaxial de folíolos posicionados nas partes superior e inferior das plantas. Para aplicar a solução traçadora, utilizou-se pulverizador com barras de 14 metros, com e sem assistência de ar, volumes de 60 e 100 L.ha-1, e velocidade do ar correspondente a 50% da rotação máxima do ventilador. Após a aplicação, os coletores foram lavados individualmente em solução extratora de ácido nítrico a 1,0 mol.L-1, e a quantificação dos depósitos através de espectrofotometria. A assistência de ar não influenciou na deposição da calda tanto a 60 quanto a 100 L.ha-1. O maior volume proporcionou maiores depósitos, sendo constatadas elevadas perdas para o solo (mais de 60%).

Coating Uniformity: Influence of Atomizing Air Pressure

The objective of this study was to investigate the influence of atomizing air pressure on the coating uniformity and the quality of the film coat. As parameters describing the coating uniformity, the mass variance of the film coated tablets and the variance of the film thickness within a tablet were used. For the examination of the properties of the film coat, the cumulative frequency of the tablet mass, the spray loss, the relative frequency of the film thickness, the minimum amount of polymer required for an enteric coating, and the swelling number were taken into consideration. For this study a Walther Pilot spray gun WA 50 with a liquid orifice diameter of 0.5 mm and a flat jet air cap was used. The experiments were carried out in a Bohle BLC 5 drum coater using four different atomizing air pressures between 0.5 and 2.0 bar. All other parameters were kept constant during the coating process. It could be shown that atomizing air pressure is an important factor influencing the quality and uniformity of a film coat. An increase in the atomizing air pressure will produce smooth tablets with a small mass variance. Due to a greater spray loss, the required minimum amount of polymer for an enteric coating is higher at an atomizing air pressure of 2.0 bar.

PM—Power and Machinery: Assessment of Recycling Tunnel Sprayers in Mediterranean Vineyards and Apple Orchards

The use of air-assisted recycling tunnel sprayers in Mediterranean fruit orchards and vineyards was assessed by comparing the performance of two tunnel sprayer prototypes with an air-assisted axial flow sprayer. Field trials comprised measurements of spray deposit on the canopy, off-target spray losses and the biological efficacy of chemical applications. According to the results, no spray drift was measured during the applications with tunnel sprayers. Spray losses on the ground were localized mainly under the crop rows. However, the uniformity of the spray deposition on the canopy was worse than that obtained with the axial flow sprayer. It seems that this can be attributed to poor adjustment of the tunnel dimensions in relation to the crop size or to inadequate air-jet design. Tunnel sprayers may be an option to meet future environmental requirements for spray applications, so long as crop training systems change to smaller-size orchards and wall-shaped trellis vineyards.

Spray deposits and losses in different sized apple trees from an axial fan orchard sprayer: 2. Effects of spray quality

Two field experiments compared spray deposits and losses from very fine (volume median diameter (VMD)=156 μm), fine (VMD=198 μm) and medium (VMD = 237 μm) quality spray applications to young dwarf, dwarf and semi-dwarf apple trees from an axial fan orchard sprayer fitted with hydraulic hollow cone nozzles. All other spray application variables were kept constant. In one experiment, the very fine quality treatment deposited slightly but significantly less spray on leaves than the other treatments but there were no significant differences in the other. The very fine spray quality treatment deposited significantly less on fruitlets in both experiments, but differences were small. The leaf-to-leaf and tree zone-to-tree zone distributions of deposits were not affected significantly by the spray quality. The percentage spray cover, estimated by image analyses, on water-sensitive papers fixed horizontally in the middle of the trees was not markedly affected by spray quality though values were variable. The very fine and fine spray qualities gave significantly greater grand mean percentages of spray drift than the medium spray quality treatment in one experiment, though differences were either not or only just statistically significant in the other. Drift was greatest in the small trees and least in the large trees, consistent with an inverse relationship with tree area density (TAD). The medium spray quality gave significantly smaller deposits on the ground sampling lines than the very fine and fine treatments. In conclusion, variation in spray quality over the range investigated did not greatly affect the amount or macro-distribution of spray deposits on apple trees from the axial fan sprayer. The coarser sprays gave slightly greater mean deposits and smaller spray losses and are preferable from these points of view. Further work is required to establish the effects of spray quality on the micro-distribution of deposits on the target. A coarser pattern of spray deposition on the plant surface could be less efficacious biologically for some pesticides. Therefore, evaluation of the effects of spray quality adjustment on biological efficacy is required.

PA—Precision Agriculture: Variation of Spray Deposit and Loss with Air-jet Directions applied in Orchards

Axial fans with a radial air flow have been most commonly used in fruit growing areas. These generate a large radial plume which is poorly targeted for modern intensive orchards. A high-volume directed air-jet system (HVDAS) sprayer, based on a standard axial fan has been developed to determine the influence of the air jet direction generated by the sprayer on the in-canopy spray deposit and off-target loss in orchards of different tree row volumes. Three sprayers with axial fans but with different air discharge systems were compared (conventional, cross-flow, HVDAS with the air spouts directed at 20 and at 40° upwards). The treatments were carried out in dwarf and semi-dwarf orchards. In modern orchards, the HVDAS sprayer with air spouts set 20° upwards produced a higher in-canopy deposit and a lower off-target loss than the conventional and cross-flow sprayers. Further raising of the air spouts directing the air-jets at 40° upwards, increased the spray loss and enhanced the risk of airborne drift without any influence on spray deposit.

The Performance of an Air-assisted Sprayer operating in Vines

The performance of a sprayer fitted with two vertical adjustable air outlets has been studied in vineyards investigating the effects of changing the fan speeds (1400, 2000 and 2500/min) and the direction of the air-jet (90 and 120° backward angle of the outlet side deflectors in relation to the treated row). Laboratory measurements were made before the field trials in order to define the operating characteristics of the sprayer.The sampling methodology in the vineyard was based on a framework and a system of intersecting nylon threads dividing the canopy into elementary volumetric zones. The spray flux entering and leaving the canopy, and the losses to the ground and to the air were measured. The spray coverage on the leaves at different heights and depths in the canopy has been also quantified.In all the tests, the air outlets were adjusted to localize the spray application to the appropriate heights determined by the growth of canopy.Considering the spray deposit and the environmental losses, the best results were observed with the 120° backward angle of the outlet side deflectors and the low and medium fan speeds. The effect of the fan speed compared with that of the direction of the air stream appeared more evident. The spray losses doubled by increasing the fan speed and frequently these losses were not limited to the treatment area but drifted outside.The degree and the uniformity of the spray coverage were strongly influenced by the high fan speed.

Identifying sources and sinks of scalars in a corn canopy with inverse Lagrangian dispersion analysis: II. Ammonia

An inverse Lagrangian dispersion analysis was used to infer sources and sinks of ammonia (NH 3) in the canopy of a dense corn crop (LAI∼5) subject to frequent sprinkler irrigation with dairy effluent. Source strengths were calculated for four canopy layers using statistics of the canopy turbulence and measurements of atmospheric NH 3 concentrations at six heights within the canopy and two above it. The analysis was performed for 4 days of measurement, two immediately following and two several days after effluent application. The analysis provided estimates of the net loss of NH 3 from the canopy, which agreed well (within 20%) with conventional aerodynamic estimates of the flux of NH 3 in the crop boundary layer. In addition, it permitted an examination of processes of loss within the canopy. Small, but not insignificant NH 3 losses were inferred for the soil. These ranged from 4% of the total loss several days after effluent application to 30% on the day of application. Unexpectedly large losses occurred from the foliage in the top half of the canopy. Calculations of apparent ammonia compensation points for the corn leaves indicated that even days after the surface water had evaporated, compensation points were too high for the loss to be explained by diffusion through stomata. It was surmised that the loss was from residues remaining on foliage surfaces. Volatilization losses from the developed crop were estimated to be about 30% of the N applied, 18% coming from soil and foliage and 12% from spray losses during effluent application.

Assistência de ar na deposição e perdas de produtos fitossanitários em pulverizações na cultura da soja

Com o objetivo de se comparar a deposição e as perdas em pulverizações na cultura da soja dois pulverizadores tratorizados de barra sendo um convencional (Condor M12-Jacto) e outro com assistência de ar junto a barra de pulverização (Columbia Vortex-Jacto) foram calibrados para aplicar 100 L ha-1, respectivamente das soluções de NaCl e KCl a 2% (p/v) à pressão de 207 kPa (30 lbf pol-2)e velocidade de 6 km h-1. Ambos os equipamentos utilizaram bicos de jato plano tipo API 110-1,5 espaçados a 0,5 m trabalhando a 0,4 m acima da cultura. A avaliação da deposição deu-se em folhas das partes superior, média e inferior das plantas e as perdas para o solo em alvos artificiais (placas de fórmica) distribuídos no interior da cultura de soja. Além desse alvo artificial outros tipos de coletores (limpadores de cachimbo) também foram utilizados em ambos os lados da cultura para se estimar a deriva. Os resultados mostraram que não houve diferença significativa na deposição entre os equipamentos em teste na parte superior das plantas de soja, mas houve diferença significativa nos depósitos obtidos nos terços médio e inferior, com vantagem para o equipamento com assistência de ar. A deriva foi consideravelmente maior para o equipamento convencional nas mesmas condições meteorológicas.

Influence of Spray Application Parameters on Deposition in an Asparagus Crop

A commercial air-assisted sprayer was tested in asparagus crop using a water-soluble food dye as a tracer. The machine had been modified by lowering the nozzles and the air outlets by 20 cm, in order to match more close by the geometry of the asparagus crop canopies and to improve deposition at the base of the stems. Several tests were performed to investigate how deposition was affected by various treatments, including: the number, position and size of the nozzles; the spray volume rate; the presence or absence of air assistance; the spray output angle, relative to the travel direction; and the forward speed. The most uniform deposition was obtained with: four nozzles per side (the lowest at a height of 46 cm from the ground), directed horizontally; an air flow rate of 6·1 m3/s; and a forward speed of 1·69 m/s. This adjustment was eventually compared with the standard sprayer setting, showing that total deposition on the canopy could be increased from 48·4 to 65·6% of the dose applied, without substantially increasing spray losses to the ground.

Development and evaluation of a method for the design of spray applications: aerial tebufenozide applications to control the eastern spruce budworm, Choristoneura fumiferana (Clem.)

A novel approach to the design of insecticide spray applications was developed and evaluated in field trials to assess the efficacy of the insect moulting hormone analog tebufenozide (Mimic ®) against the eastern spruce budworm, Choristoneura fumiferana (Clem.). The pest biology, and habitat and pesticide characteristics were used as a basis to derive the required active ingredient (a.i.) and deposit density. Ingestion is the primary exposure route; an LD 95 acquisition through foliage consumption by fourthinstar larvae was used to establish a target dose of 15 ng a.i. cm −2 in one drop per needle (2.5 cm −2). A range of a.i. and volume application rates were selected based on the required densities, canopy leaf area index and projected spray losses to the understorey and by drift; application rates of 35, 70 and 140 g a.i. 1 ha −1 were employed, with volume application rates of 1, 2 and 4 L ha −1. Coniferous forest plots were aerially treated, resulting in average deposit densities (droplets cm −2) on artificial foliage between 0.8 and 3.7, with averge volumetric deposits between 7 and 30% of volume application rates. Population control was satisfactory, except for those applications at 35 g a.i. in 2 L and 70 g in 4 L ha −1 for which low deposit densities were observed. This approach to spray application design was found to be of scientific value and is adaptable to other insecticide applications.

Losses from low-pressure center-pivot irrigation systems in a desert climate as affected by nozzle height

A study of spray losses from three low-pressure center-pivot sprinkler irrigation systems was carried out under field operating conditions. The evaporation losses during sprinkling were determined at three different spray-nozzle heights from ground surface. The average values were 15.63, 21.19 and 35.77% for heights of 1.25, 1.75 and 2.5 m, respectively. In addition, the three center-pivot systems were evaluated. The values for the distribution uniformity, the potential application efficiency, and the uniformity coefficient were calculated.

The distortion by wind of the distribution patterns of single sprinklers

The distribution patterns of sprinklers are modified, under field conditions, by drift, evaporation and distortion, caused by wind and evaporative demand of the air. To evaluate experimentally spray loss (evaporation plus drift), collector evaporation must be suppressed or corrected for. Here an approximate correction, based on the measured evaporation from peripheral collectors, was applied to the data. It was further assumed that spray loss is distributed over the pattern in proportion to the local rate of water application. Based on experimental results, a set of wind distorted patterns for wind speeds of 0, 2, 4, 6 and 8 m/s was obtained. These can be used for simulation under conditions similar to those encountered during the experiment. The patterns can be interpolated for any desired wind-speed, rotated to the required direction and then corrected for the spray-loss appropriate to the environmental conditions.

Performance of Stationary Gun Irrigation Systems

The field performance of stationary giant gun irrigation systems is evaluated from the results of 70 distribution tests conducted in the interior of British Columbia, Canada. Three measures of field performance are quantitatively evaluated including maximum application rate, evaporation and spray loss and distribution uniformity. Maximum application rate is found to be a function of average wind speed in the principal wind direction. Evaporation and spray losses were dependent on climatic and operating conditions, primarily the atmospheric vapor density deficit and the average wind speed. The uniformity of application is strongly influenced by both the gun spacing and the average wind speed. The influence of operating variables such as nozzle size and pressure are accounted for in the parameters used to nondimensionalize these relationships. The equations representing these findings are derived using multiple regression and are presented algebraically. Measured values are plotted against predicted values to give a visual impression of scatter in the data. The utility of the relationships in designing and operating giant gun systems is illustrated.

Spray Losses and Partitioning of Water Under a Center Pivot Sprinkler System

ABSTRACT CENTER pivot irrigation is extensive in the Great Plains agricultural region. The efficiency of a center pivot sprinkler system was analyzed by monitoring spray losses under various climatic conditions and by examining the partitioning of water within a corn (Zea mays L.) canopy. Average spray losses were 12% in 1980 and 16% in 1981. Spray losses were significantly correlated with vapor pressure deficit (r^ = 0.49), temperature (r,^ = 0.47) and a wind-vapor pressure deficit term (rXjy = 0.45). The unexplained variability in the data may be attributed to the difficulty of determining the exact application rate at a particular area of the field and to the interaction between climatic conditions and wind orientation relative to the sprinkler lateral. Under full canopy condition in corn, about half of the water reaching the soil surface is via stemflow with the remainder falling or dripping through to the soil surface. We found 2.7 mm of canopy storage in a full corn canopy. Net loss of plant intercepted water depends on the temperature and on the ratio of canopy (rc) and aerodynamic (ra) resistances to vapor flux, with net losses being small if rc/ra is low and temperatures are high.

Distribution of Irrigation Water from a Low Pressure, Lateral-Moving Irrigation System

ABSTRACT FUNDAMENTAL considerations for irrigation water applications from lateral-moving irrigation systems are presented. The application dynamics are discussed relative to low-pressure, lateral-move irrigation machines. A prototype low pressure, lateral-move irrigation system was evaluated by testing several applicator systems for low volume, frequent irrigations. Results indicated that static uniformity coefficient exceeded 0.98. However, the dynamic uniformity coefficient was about 0.90. Pressurization requirements can be reduced to less than 200 kPa (possibly as low as 100 kPa) with little reduction in uniformity. The spray losses (both drift and evaporation) from the low pressure, overhead spray systems were about 10%. System alignment and, particularly, system speed control appear important to achieving uniform applications with low-pressure, lateral-moving systems. Additional research on speed control technology appears desirable.