Spray planning a must for growers
Author: Toni Somes | Date: 23 Feb 2018
Targeted and effective chemical spray applications start well before the spray rig even leaves the shed.
That’s according to Nufarm Australia spray application specialist Bill Gordon who will discuss the importance of adjuvant selection and using nozzle spray quality data during presentations to the Grains Research and Development Corporation (GRDC) Grains Research Updates in Dubbo on Tuesday, February 27 and Wee Waa on Thursday, March 1.
With herbicides and pesticides accounting for up to 30 per cent of variable input costs in grain production, Australian grain growers are eager to ensure that applications are effective and spray drift is minimized by accessing the latest product information and best practice recommendations.
“Advisors and growers need to critically evaluate the claims made on adjuvant labels or in technical literature about the products they plan on using, as well as the spray quality data for nozzles supplied by their manufacturers for legal compliance, efficacy and drift control,” Mr Gordon said.
Adjuvant selection plays a key role in herbicide performance and can modify the physical, chemical and biological activity of the herbicide on the target.
The most obvious effect of adding an adjuvant to the spray solution is a change in the dynamic surface tension, according to Mr Gordon.
Lowering the surface tension causes droplets to spread on the leaf surface, which can increase contact with the leaf surface, improving uptake.
However, reducing surface tension of the spray solution can also modify how the droplets themselves are formed as they leave the nozzle, typically reducing their size (compared to water alone).
“One of the main factors influencing the droplet sizes produced by a nozzle is the nozzle design itself, that is, some nozzles are coarser or finer than others,” Mr Gordon said.
“The spray solution also has an influence, where products with a lower dynamic surface tension tend to produce finer droplets than product with a higher dynamic surface tension.
“Other factors including viscosity and solution temperature can also impact on how droplets are made through various nozzles.”
Mr Gordon said that nozzle selection was a critical part of spray management and urged growers to base their decisions on current spray quality information such as the GRDC Spray Quality Guide 2017.
Spray quality is not a direct measure of drift but a measurement of the range of droplet sizes produced by a nozzle.
Spray quality data may be reported by nozzle manufacturers against a couple of different standards including the British Crop Protection Council (BCPC) or the older American Society for Agricultural Engineers (ASAE) Standard S572, which are both mentioned on some Australian labels.
Both the BCPC and older ASAE standards report spray quality based on water alone being sprayed through the nozzle.
Mr Gordon said some changes to the standards for spray quality had recently been adopted, requiring that testing of pre‐orifice and air induction nozzles include the addition of a 40 dynes/cm adjuvant to water as the test solution.
“This has been designed to provide data that better reflects the spray quality that a typical tank mix may produce, rather than water alone,” Mr Gordon said.
“As a result, recent nozzle charts may show spray qualities that may appear to be finer than older charts that may still be in circulation. It is important that nozzles are selected based on the best available data.”
The two-day Dubbo GRDC Update is being held on February 27 and 28 and incorporates a range of topics and presenters including Cam Nicholson who will discuss the use of temperament typing to encourage practice change, Andrew Smart of PCT on how to turn NDVI and yield maps into profitable decisions, Peter Hayman from the South Australian Research and Development Institute on understanding and managing frost risk, David Lamb from the University of New England on setting the farm up for automation, and Melbourne University’s Paul Umina on managing insecticide resistance in Helicoverpa armigera.
The Wee Waa Update is being held on Thursday, March 1 at the Imperial Hotel and speakers include Felicity Harris from New South Wales Department of Primary Industries (NSW DPI) on using phenology to manage frost risk in wheat, Andrew Verrell from NSW DPI on factors affecting flowering, pod set and yield in chickpea, Kerry McKenzie from the Department of Agriculture and Fisheries Queensland on chickpea water use efficiency and Moree district grower Nick Gillingham on setting up the farm for broadband connectivity.
For a full list of speakers and to register for the Dubbo Update, go to the events page on the GRDC website, for a Wee Waa program and to register follow this link or contact ICAN on 02 94824930 or firstname.lastname@example.org.
Bill Gordon, Nufarm
0418 794 514
Toni Somes, Cox Inall Communications
0427 878 387
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