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To ensure that grape growers can achieve good coverage and maximum efficacy with agricultural plant-protection products and to assess Drift Reduction Technologies (DRTs) to minimise spray drift potential.
Abstract
Studies were conducted in wind tunnels and vineyards to show the performance of various factors that affect spray coverage on different canopy regions and losses through runoff and drift. These factors included different combinations of nozzles, adjuvants, electrostatic charging, recapture systems, air targeting, barrier vegetation and netting. The best system for any given application will depend on the target. For example, for herbicide applications, coarser sprays can be achieved using the droplet size data, whereas for foliar-applied sprays, the finer sprays can be optimally directed to their target including inner canopy areas using lateral air or radial air with deflector air at the top. Recapture-recycling sprayers offer an additional benefit to those listed above in that the small amount of spray that misses the target is caught and can be reused, reducing losses to almost zero. Electrostatically-charged sprays offer excellent coverage on all leaf surfaces but can drift under adverse conditions due to the very small size of the droplets. Barriers are very effective at capturing most drift, so electrostatic sprays may be safer where there are barriers downwind of the vineyard.
The data from this project support new national regulations that will offer applicators greater choice to achieve smaller no-spray buffers than they would otherwise have had, with previous regulatory reliance on the U.S. AgDRIFT model. By introducing an Australian reference sprayer, this project provided a bridge for comparison of all Australian sprayer performance data, through this project and any future research, to gain credit in the upcoming new national drift regulatory scheme. The droplet size and drift potential data from the wind tunnel are provided in a format ready for loading into a novel spray calculator coverage and drift performance App following the finalisation of this scheme, which is expected by the end of 2017.
The research showed that canopy wall area-based calibration is superior to ground area-based calibration.
Simple tools are available for the assessment of spray performance in vineyards, such as fluorescent tracer dyes and image analysis. Appropriate resolution of at least 4800 DPI is required for the latter.
Objectives
To ensure that grape growers can achieve good coverage and maximum efficacy with agricultural plant-protection products and to assess Drift Reduction Technologies (DRTs) to minimise spray drift potential.
Background
Pesticide application technology underpins all rural industries in Australia. Until recently it was an area of agricultural science that operated from research that was mostly conducted several decades ago. There has been very little research in new spray technology and although most spray applicators have some basic accreditation there is an urgent need for rigorous research to improve spray practices in Australian viticulture. Information in the literature shows that when vineyards are sprayed, up to 60 per cent of the applied material can end up on the ground rather than on the canopy. Also, there are challenges in achieving uniform coverage on the target without off-target wastage of product. The project will address these issues and show how to avoid product wastage by spray adjustment for the canopy and spray optimisation for efficacy.
Approach
Wind tunnel experiments will be conducted at the University of Queensland. This facility is equipped with laser-diffraction instruments, a copper-vapour laser imaging instrument and a phase-Doppler particle analyser. All droplet sizing work will be conducted using these instruments and a number of spray nozzle types, nozzle pressures and chemical formulations will be evaluated. The wind tunnel experiments will guide and complement field trials in South Australian and Queensland vineyards, which will optimise spray application using Light Detection and Ranging (LiDAR) and sensor sprayers on a range of grape canopies of different heights. Various spraying systems will be evaluated utilising recapture and recycle techniques to reduce spray volumes, losses to the ground and drift as well as electrostatics and optimisation of conventional airblast and rotary fan systems.
Sector benefits
Through this project, growers will be able to achieve good spray coverage and optimised chemical efficacy while simultaneously reducing overdosing that often occurs with small grape canopies and the under dosing of larger canopies. The project will drive innovation in the industry with DRTs that reduce buffer zones.
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