Ground Cover Supplement : GC Supplement - Spray application 2016
21 Applicator toolbox TIPS FOR GETTING THE BEST RESULTS FROM WSP AND THE SNAPCARD APP The amount a droplet will spread on water-sensitive paper is known as the spread factor. This is influenced by formulation and humidity, and when these factors are known, the size of the original droplet can be calculated. FAST FACTS ¢ Download the SnapCard instruction manual from the website (http://agspsrap31.agric. wa.gov.au/snapcard/#manual) before you start and practise using the app before commencing any trials. ¢ Water and oil-sensitive paper (WSP) cards are available through TeeJet distributors such as machinery dealers. ¢ Always use disposable gloves when handling WSP cards, even fingerprints and sweat can produce a stain on them. ¢ Consider the position of the WSP cards in relation to the sprayer. It is a good idea to set an A–B line for the sprayer, or note the wheel tracks and then place pegs in the ground where the cards are located. Even in fallow WSP cards can be hard to locate. ¢ Do not try to use WSP cards when the relative humidity is above 70 to 80 per cent, as the cards will turn blue. Place out a single test card to assess this before commencing any trial. ¢ Place several cards out at each location you wish to collect coverage data from. After measurements of spray coverage are completed, record an average for the group of WSP cards at that location. ¢ Allow the cards to dry fully before collecting them. ¢ Label the back of each card with a pencil for future reference and store them separately in snap-seal bags to avoid exposure to moisture or humid conditions. ¢ After collecting all the WSP cards, go to a place out of the wind where you can use SnapCard to take individual pictures of all of the WSP cards in one session, keeping the smartphone camera height at a constant distance from the WSP cards, and under uniform light conditions. ¢ Once they have been measured with SnapCard, the cards can be photographed or glued to a sheet of paper and scanned. It is a good idea to include details of each treatment and the sprayer set-up in the photograph or scan. ¢ Keep the results of all of your tests in one book or folder for future reference, making sure you record all of the application parameters and conditions for each test. Measuring spray coverage with SnapCard to identify areas of improvement Many operators may not have considered the number of situations where an accurate measurement of the coverage could be useful for improving the sprayer set-up. While the following examples may not include every possible use of SnapCard, they do provide a useful guide for how to look at specific situations. Assessing penetration into crop canopies Placing WSP cards directly onto the crop canopy using staples or paperclips at various heights throughout the canopy can demonstrate how much penetration into the canopy can be achieved with different application set-ups. The images in Figures 2 and 3 and Table 2 are from an example of using WSP cards and SnapCard provided by Bill Campbell of Farmanco Management Consultants in Western Australia. In this example, Mr Campbell worked with one of his clients to improve the spray coverage in canola for Sclerotinia sprays. Figures 2 and 3 show the difference in coverage on WSP cards that a change in spraying speed with the same nozzles can produce, with the results summarised in Table 2. Assessing spray deposits into standing stubble To assess if the sprayer is set up to provide good spray deposition into standing stubble a comparison needs to be made between the spray deposits in the inter-row space and at the base of the standing stubble (within the stubble row). If a sprayer set-up can produce good spray coverage that is equivalent between the two locations, it generally indicates that the spray operator has selected an appropriate spray quality and application volume for stubble load and the spraying speed tested. Determining wake effects and wheel-track issues Placing WSP cards at different positions across the boom sprayer allows spray operators to look at the impact of changing travel speed on the amount of spray that deposits in the centre of the sprayer, adjacent to the wheels and out under the boom. This information is useful for looking at wheel-track issues and adjustments that can improve coverage. Fine-tuning pulse-width modulation -- highlighting coverage and duty cycle Placing WSP cards at regular intervals, usually with a 2.5-centimetre gap between the cards, onto strips of timber that are at least one metre long can highlight possible coverage concerns if the duty cycle of a pulse-width modulation (PWM) system is too low to provide even coverage. Aligning the strips of timber with the direction of travel and spraying at different speeds will show the impact of low duty cycles, particularly with coarser spray qualities. Identifying suitable travel speeds and sprayed widths with target-selectable sprayers Placing cards on strips of timber aligned with the direction of travel, as described for PWM (see page 18), can quickly illustrate when the individual sprays turn on and off in relation to the position of a weed for target-selectable sprayers. Often it is useful to ensure the area for the trial is free of any green vegetation that might trigger the cameras, and to deliberately transplant weeds into the test area. Often when the spraying speed is not correct the spray droplets will deposit onto the WSP cards well before or well after the position of the weed. The same timber strips, but this time aligned perpendicular to the direction of travel (parallel to the boom), with the centre of the strip aligned with the weed can show the sprayed width when the machine is operating at its usual spraying speed.
GC Supplement - Tactical cereal agronomy
GC Supplement - More profit from crop nutrition II