Modification of an Open-Circuit, Push-Through, Low-Speed Wind Tunnel to Assist Pesticide Spray Application Advancements

Highlights The effectiveness of four nozzles with flat-fan spray pattern types was evaluated to assess their ability to deliver spray droplets inside the soybean canopy in a wind tunnel equipped with a moving boom. The effect of wind speed on the spray coverage, deposition, and airborne drift of droplets discharged from the four evaluated nozzles was investigated under the wind speeds of 0, 2.4, and 5.1 m s-1. Spray deposition at the bottom part of canopies was significantly lower than at the upper part. Nozzles that produced ultra-coarse droplets reduced airborne spray drift risks. The dense soybean canopies and overlapping foliage of crops limit the spray droplet penetration capability of the hydraulic nozzles. ABSTRACT. Adequate spray deposits and coverage in the middle and lower parts of the canopy are essential to protect soybean crops from disease and insect attacks. Additionally, uncontrollable weather conditions can influence the effectiveness of spray applications. Thus, the objective of this research was to evaluate the effect of the wind speeds of 0, 2.4, and 5.1 m s -1 on the spray coverage and deposition discharged from travelling nozzles with different droplet sizes under wind tunnel-controlled conditions. An open-circuit wind tunnel, equipped with a moving spray boom placed 0.5 m above the top of the soybean canopy and operating at a speed of 0.9 m s -1 , was used in this study. To achieve the application rate of 150 L ha -1 , pulse width modulation solenoid valves were coupled with the nozzles at a duty cycle of 19% and an operating pressure of 276 kPa. Four types of same color-coded 110° flat-fan spray nozzles (XR11004, TTJ6011004, AITTJ6011004, and AIXR11004) were used to determine the effects of spray droplet size spectra Keywords: Centrifugal fan, Laminar flow, PWM nozzle, Spray deposition, Spray drift, Traveling boom, Turbulence.