A wedge shaped bluff plate air-assisted sprayer: III. High-speed, low volume herbicide spraying in dryland field cropping systems

G.O. FurnessA, M.M. WearneB, J.J. HastingsC P.S. BartonD and C.B. DysonE

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 boom sprayer, consisting of a wedge shaped bluff plate placed in front of the nozzles, was used to apply herbicides in a spray volume of 20-30 L ha-1 at 30 km h-1 in field cropping situations. Low volume, fine, hollow cone and conventional flat fan nozzles were used in conjunction with the bluff plate. Results were compared to a conventional (non air-assisted) spray boom with flat fan nozzles. In several of the trials, a treatment was included using ultra-low-volume applications of herbicides, formulated in petroleum spraying oil and sprayed without water at 2-4 L ha-1 total spray volume using slotted rotary sleeve atomizers.

Thirteen herbicide efficacy trials were conducted in 1989 and 1990. Herbicides were applied to bare soil for pre-emergent weed control, to newly emerged weeds prior to sowing, to weeds early post emergence in the crop, and to pastures for seed set control (pasture topping) to control weeds in the crop for the following season. Herbicide efficacy in all situations was relatively consistent regardless of treatment (presence or absence of a bluff plate and nozzle type). Herbicides applied in petroleum oil at 2-4 L ha-1 without water gave similar or slightly reduced efficacy to conventional herbicide applications, and therefore warrant more detailed evaluation.

Earlier work with a simple bluff plate (Furness 1991), and work reported by Young (1996), established the ability of the bluff plate to virtually eliminate sideways spray drift even in windy conditions. Thus the main commercial advantages of the bluff plate sprayer are the ability to operate with consistent efficacy in a wide range of wind conditions, combined with a high work rate, (due to higher travel speeds and lower spray volumes). These features enable spray timing over large areas to be closer to the optimum for weed control.

 

Plant Protection Quarterly (2001) 16 (3) 101-107.