Ground Cover Supplement : GC Supplement - Spray application 2016
16 Decision support The operators’ toolbox just got bigger New tools for assessing the impact of tank mix, nozzle type and operating parameters on sprayer output are now available to help operators better manage their spray jobs By Dr Andrew Hewitt, Dr Chris O’Donnell and Dr Gary Dorr THE CHOICE OF nozzle, spray pressure and tank mix composition, including active ingredient and adjuvants, underpins the performance of pesticide spray in terms of cover and spray drift. In general, the coarser the spray, the lower its drift potential but also the lower the potential coverage on many target surfaces, plants and pests. Increasing the water volume rate can help boost droplet numbers, but it can still be a challenge to get the right balance between spray coverage and reduced drift in the face of so many variables. Adjuvant effects are often not particularly intuitive -- some adjuvants will increase the number of fine droplets in a spray, while other products may reduce them. To make things more complicated, different nozzles can have different results and variations can also occur between the outputs from different orifice sizes of the same type of nozzle. As a part of GRDC-funded projects, University of Queensland (UQ) researchers have measured the performance of more than 1000 combinations of nozzle, pressure and tank mix that cover many Australian grain crop spraying scenarios and have assembled this data into the new Australian Spray Performance Calculator. This tool has been developed to provide reliable information to take some of the guesswork out of spray performance and help operators improve their drift-management strategies. Some of the data used to develop the Australian Spray Performance Calculator has also been supplied to the Australian Pesticides and Veterinary Medicines Authority for inclusion in tools that may be approved for use in calculating modified downwind buffer distances as a part of proposed label changes. The Australian Spray Performance Calculator is able to show many of the key performances of a spray in relative terms: ¢ potential coverage in number of droplets per square centimetre; ¢ areas covered on the target after droplets have deposited; ¢ spray quality, in terms of droplet size classification; and ¢ spray-drift potential, indicated as percentage of fines produced. There will also be other features to provide additional information about spray output, supported by images of what spray deposits may look like on collectors such as water-sensitive paper. The new tool is available as a spreadsheet (supported by a regularly updated database of information) that can be run on any computer and smartphones or tablets equipped with an Excel reader. Users can select from a list of drop-down options to enter all of the parameters about their spray, including: ¢ nozzle type: the nozzle types and orifice sizes cover 10 manufacturers, with all data tested independently by UQ using a single test system to ensure comparisons between nozzle outputs are consistent; ¢ pressure and fan angle: the user selects the spray pressure and the spray angle (for example, 110º for a 110-02 nozzle); ¢ tank-mix properties: details of the tank mix (water or a pesticide selected from a list of active-ingredient products in Australia and adjuvants); and SOURCE: UNIVERSITY OF QUEENSLAND The Australian Spray Performance Calculator main screen for data input: having access to a tool that can provide coverage information, droplet size data and drift potential specific to the nozzle, tank mix and operating parameters is a leap forward for spray applicators.
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