Spray Chamber Evaluation of Air‐Assisted Spraying on Broccoli

Abstract

an increase in leaf coverage for the top leaves with increasing airspeed, and a better coverage in the middle Conventional over-the-row sprayers achieve very little deposit on of the canopy at full airspeed. At 94 L ha Ϫ1 , the top leaves near the ground and on the underside surfaces of leaves throughout the canopy. Air assistance has the potential to improve leaf coverage was not affected by increasing airspeed. deposition of droplets on these leaf surfaces. To gain some insight However, middle leaf coverage of the canopy was the on the effect of air assistance, the effects of airspeed, airflow rate, best at the highest airspeed. and air jet orientation were isolated. The study was carried out in On potatoe (Solanum tuberosum L.), Cooke et al. a spray chamber with a standard spray boom over micro-plots of (1990) obtained a better coverage for the middle and greenhouse grown broccoli (Brassica oleracea var. botrytis L.) plants.lower parts of the canopy with high airspeed (36 m s Ϫ1 ). Air was delivered slightly behind the nozzles from a variable widthThe coverage of the top leaves was the best at a medium slot producing a uniform two-dimensional air jet. The orientation of airspeed (25 m s Ϫ1 ). Jeffrey and Taylor (1991) used a the air jet with respect to the vertical could be adjusted from Ϫ10 to Hardi Twin air-assisted sprayer at three airspeeds (15, 40؇. The ranges of the independent variables were airspeed, 0 to 36 22, and 28 m s Ϫ1 ). On the upper side of leaves, they m s Ϫ1 ; airflow rate, 0 to 1.3 m 3 s Ϫ1 m Ϫ1 , and air jet angle, Ϫ10.2 to 40.2؇. Two sets of flat fan nozzles (Volume Median Diameter ϭ 230found that the coverage in the upper section of the and 400 m, both delivering 250 L ha Ϫ1 at 6 km h Ϫ1 ) were used to canopy was lower with increasing airspeed while at the carry out two full sets of experiments. Results showed that airspeed

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

“…The combination between air assistance and the +30° angle provided a deposition increase in the order of 74 and 75%, respectively, for upper and lower positions in the plant, while for 0° angle the increasing deposition was of the order of 85 and 84%, respectively, for the upper and lower positions when compared at the same angles, for air assistance absence, in accordance to results obtained by Panneton et al (2000) and Leonard et al (2000). For the -30° angle, a completely divergent fact occurred: deposition without air assistance was greater on the abaxial surface than with air assistance, both at the higher and at the lower positions.…”

“…Panneton et al (2000) also verified that air assistance modifies the vertical gradient of deposits, providing better uniformity in the deposition at different positions within potato plants.…”

“…In order to improve the fungicide application to a field crop, sprayers have been equipped with air-assistance booms, which allow a directed spray mix flow thus avoiding drift losses (Cooke et al, 1990;Bauer & Raetano, 2000). They also provide better product distribution and deposition on the abaxial surface of leaves of the lower parts of the plant (Leonard et al, 2000;Panneton et al, 2000;Venegas, 2002;Scudeler & Raetano, 2004), increasing the penetration of droplets into the crop canopy (Matthews, 2000), as well as reducing spray deposit variability (Venegas et al, 2003).…”

Effect of spray angle and spray volume on deposition of a medium droplet spray with air support in ivy pot plants

“…These results illustrate that the optimum spray angle depends on the part of the canopy to be protected . They also suggest that the 30° and the 0° angle are more likely to result in a more even distribution of the spray.…”

“…Many studies describe that angling the nozzles is an efficient, easily adjustable and inexpensive way to improve the deposition or penetration in the canopy . The use of air support or a combination of both air support and an angled spray have also showed promising results in other studies. Finally, treating the crop from two directions has also been suggested to improve spray results, especially to overcome a lower deposition on the back side of the plants …”