Search

Because of variations in environmental conditions, spray-drift field measurements following ISO 22866:2005 involve complicated and time-consuming experiments often with low repeatability. Therefore, simple, repeatable, and precise alternative drift assessment methods that are complementary to the official standards are required. One of the alternatives is the use of a drift test bench for field crop sprayers. Previous studies have demonstrated that the drift test bench can be considered an adequate complement to existing standard protocols for field drift measurements. In this study, in order to further improve the methodology and to evaluate the possibility of classifying different field-crop-sprayer settings according to drift risk using a test bench, a series of tests were performed in a test hall. A conventional mounted Delvano HD3 crop sprayer (Delvano, Kuurne, Belgium) equipped with an 800-l spray tank and a 15-m-wide stainless steel spray boom was used. Eight different sprayer setups were tested, involving three nozzle types (TeeJet XR 110 04, Agrotop TDXL 110 04 and Micron Micromax 3) and three boom heights (0.30, 0.50, and 0.70 m). For the drift classification, the reference sprayer drift behaviour was defined as that obtained using conventional flat fan TeeJet XR 110 04 nozzles operated at 0.30 MPa and at a boom height of 0.50 m. The different sprayer setups were successfully assigned to different drift reduction classes, and the results underlined the effects of nozzle type and boom height on the potential drift. The feasibility of the test-bench methodology for classifying field-crop-sprayer drift according to ISO 22369-1:2006 was demonstrated. [ABSTRACT FROM AUTHOR]

The use of a scanning Light Detection and Ranging (LIDAR) system to characterize drift during pesticide application is described. The LIDAR system is compared with an ad hoc test bench used to quantify the amount of spray liquid moving beyond the canopy. Two sprayers were used during the field test; a conventional mist blower at two air flow rates (27,507 and 34,959 m³·h-1) equipped with two different nozzle types (conventional and air injection) and a multi row sprayer with individually oriented air outlets. A simple model based on a linear function was used to predict spray deposit using LIDAR measurements and to compare with the deposits measured over the test bench. Results showed differences in the effectiveness of the LIDAR sensor depending on the sprayed droplet size (nozzle type) and air intensity. For conventional mist blower and low air flow rate; the sensor detects a greater number of drift drops obtaining a better correlation (r = 0.91; p < 0.01) than for the case of coarse droplets or high air flow rate. In the case of the multi row sprayer; drift deposition in the test bench was very poor. In general; the use of the LIDAR sensor presents an interesting and easy technique to establish the potential drift of a specific spray situation as an adequate alternative for the evaluation of drift potential. [ABSTRACT FROM AUTHOR]

Integration of variable-rate disc-core nozzles in orchard sprayers is the optimal solution to achieve precision spray applications of agrochemicals; however, little information is available on the droplet size distribution and classification for these hollow-cone nozzles. Investigations were performed for the comprehensive understanding of spray droplet size spectrum discharged from hollow-cone nozzles which were manipulated with pulse width modulation (PWM) valves to produce variable flow rates. Test variables included five disc-core hollow-cone nozzle sizes (D2-DC25, D2-DC45, D4-DC25, D4-DC45, and D5-DC25), two 10-Hz PWM valve designs, five operating pressures (276, 414, 552, 689, and 827 kPa), and 10 duty cycles (DUCs) ranging from 10% to 100% at 10% intervals. Droplet diameters were measured with a laser imaging particle system. Volumetric diameters (DV0.1, DV0.5, and DV0.9) varied greatly with the nozzle orifice size, operating pressure, and DUC, and varied slightly by PWM valve type. Higher operating pressures and larger nozzles generated droplets with more consistent size distributions across DUCs from 10% to 100%. The differences in relative spans among DUCs increased with the nozzle size increase and the operating pressure decrease. Droplet size classifications from very fine to coarse, based on ASABE 572.3 standard definitions, varied with the nozzle size and operating pressure but were similar for two PWM valve designs at all DUCs. Spray volume fractions also varied with the droplet size range, DUC and pressure. For droplets smaller than 100 µm, the volume fraction remained relatively consistent or slightly decreased as DUC increased, but increased as the pressure increased. In comparison, the fraction increased as both DUC and pressure increased for droplets between 100 and 300 µm and decreased for the portion of droplets greater than 300 µm. As a result, the discovered information would be implemented for the improvement of precision variable-rate spray systems equipped with PWM valves. [ABSTRACT FROM AUTHOR]

Pulse width modulation (PWM) solenoid valves are used for controlling flowrates of hollow-cone nozzles on variable-rate air-assisted orchard sprayers. However, little information is available on the spray characteristics of these PWM-controlled nozzles. Laboratory tests were performed to evaluate the influences of duty cycles of two different design PWM solenoid valves along with five operating pressures on spray characteristics of five hollow-cone nozzles with different disc-core combinations. Parameters of the spray characteristics investigated were nozzle flowrates, upstream and downstream pressures of the PWM valves, nozzle activation pressures and times, and spray angles of water discharged from nozzles. Test results illustrated that these parameters except for the spray angle were greatly affected by the operating pressure, nozzle selection (disc orifice size and quantity of holes on core), PWM duty cycle and solenoid valve design. Spray angles were affected by the duty cycle but not by the PWM valve design. In general, nozzles with larger disc orifice and higher operating pressures resulted in higher flowrates as expected, whilst the nozzle activation pressure and the spray angle decreased as the duty cycle decreased. Thus, when designing orchard sprayers for precision variable-rate pesticide applications, variations in spray characteristics of disc-core type hollow-cone nozzles controlled by PWM solenoid valves should be considered and minimised. This prospect could be facilitated by establishing a digital database of these characteristics. • Spray parameters were measured for PWM-controlled disc-core hollow-cone nozzles. • Pressures acting on PWM valves and nozzle orifices were significantly different. • Nozzle activation pressures decreased as duty cycles decreased. • PWM valve design affected nozzle pressures and flowrates but not spray angles. • Digital tables were established for improvement of precision variable-rate sprayers. [ABSTRACT FROM AUTHOR]

• Effect of fan settings and nozzle size on leaf coverage in a treatment was studied. • The higher the airflow rate and droplet size, the bigger the homogeneous coverage. • The finest droplets distribution showed a large dependence on initial fan setup. • Canopy resistance behavior was related with the turbulence intensity of air currents. • A larger turbulence intensity did not imply a better spray coverage on the trees. Air assistance and droplet's characteristics influence on the pesticide deposit and its distribution over the intended target during the spray application process. The present research work is focused on the characterization of the leaf coverage and the overall spray distribution within the whole canopy by combining different settings of air assistance with different nozzles, generating different droplet's sizes. A new designed air-assisted orchard sprayer was tested, presenting a wireless remote-regulation system to control the airflow rate from the fan by adjusting the blade pitch. In this way, five airflow rates were obtained by combining the gearbox position and the blade pitch. For each one of these five air settings, three droplet sizes (F-Fine, M−Medium, and C-Coarse) were combined and evaluated over a set of artificial apple trees. The evaluation was divided in two parts: a) a whole characterization of the airstream generated by the five air settings was performed for the two sprayer's sides using a 3D-ultrasonic anemometer and placing the sprayer in front of the artificial trees and b) a coverage tests for each nozzle-air settings combination by using water sensitive papers (WSP) placed at different heights and depths evenly distributed across the canopy, the WSP's were analyzed by a processing image software. The results demonstrated that ultrasonic anemometers were helpful to characterize the airstream and to analyze its effect on leaf coverage. Experimental data showed that a higher airflow rate and a larger droplet size generated a more homogeneous coverage on both sides of the sprayer. In this line, the turbulence intensity data suggest that larger variations in the air velocities increase the drag coefficient. Which meant that the canopy resistance to the air stream increased. In addition, an increase of turbulence intensity generated higher spray coverage. Therefore, a higher turbulence intensity did not imply a better spray coverage. It was also observed that the droplet size was critical on regulating the airflow influence on spray coverage. Coarse droplet size did not present any relation with the airflow changes. While the fine droplet size presented a high dependency on airflow conditions. [ABSTRACT FROM AUTHOR]