A wedge shaped bluff plate air-assisted sprayer: I. Spray deposits on artificial targets
G.O. FurnessA, M.M. WearneB, J.J. HastingsC, P.S. BartonD and A.B. FrenshamE
A South Australian Research and Development Institute (SARDI), Loxton Centre, PO Box 411, Loxton, South Australia 5333, Australia.
B Monsanto Australia Limited, 19 Wilton Terrace, Torrensville, South Australia 5031, Australia.
C Ian Macrow Consultants, 323 Margaret Street, Toowoomba, Queensland 4350, Australia
D Altona Street, Abbotsford, New South Wales 2046, Australia.
E SARDI, Plant Research Centre, Hartley Grove, Urrbrae, South Australia 5064, Australia
Summary
An air-assisted field crop sprayer consisting of a wedge shaped bluff plate placed in front of a spray boom was designed and used to evaluate spray deposition on small horizontal and vertical artificial targets placed at ground level. Smoke generators were used to examine air movement around and behind the bluff plate. The spray boom, fitted with high and low volume flat fan and hollow cone nozzles, and slotted rotary sleeve atomizers, was located behind the bluff plate. Results were compared with those of a conventional spray boom fitted with the same nozzles.
A number of spraying parameters were evaluated by spraying a suspension of a fluorescent pigment onto the targets and measuring the deposits using a fluorescence spectrophotometer. On vertical targets, the bluff plate treatments gave deposits that were on average about four times greater than when nozzles were used without a bluff plate. On horizontal targets, deposits were lower than on vertical targets, with no significant differences between bluff plate and non bluff plate treatments. There were significant effects due to nozzle type. In most treatments, hollow cone nozzles resulted in greater deposits than with the other nozzles, both with and without the bluff plate. However, differences between the various nozzle treatments were smaller than those due to the bluff plate and not consistent between nozzles.
As the bluff plate height above the ground was increased, spray deposits on artificial targets decreased. With the gap between the bluff plate and the ground set at zero, nozzle height had no significant effect on the quantity of spray deposited. With spray volume, the amount of pigment deposited increased rapidly up to about 15 L ha-1, then levelled off and decreased slightly to 50 L ha-1. With spraying speed, the amount of pigment deposited increased rapidly between 5 and 10 km h-1, but further increases in spraying speed, up to 45 km h-1 produced only a small further increase in the amount of pigment deposited. Mean droplet size (in the range 100-250 µm v.m.d.) had no significant effect on the amount of pigment deposited.
Plant Protection Quarterly (2001) 16 (2) 75-83.