Benefits of 250mm Spacing with Air Pro
The above graph represents the weed kill at 14 and 42 days after treatment. Focusing on the 42 days after treatment, it is clear that the standard 500mm nozzle spacing has relatively poor results compared to the two other examples which use different nozzle techniques but both operate on 250mm nozzle spacing.
This trial was conducted with 04 nozzles and standard spacing on the left hand side of the sprayer and the 250mm nozzle spacing were positioned on the right hand side of the sprayer. This means that exactly the same speed and nozzle pressure across the length of the boom was applied, eliminating these factors as variables.
There are many reasons for the better results achieved by the 250mm nozzles spacings. The first and most straightforward is that by having twice as many nozzles penetrating through the crop and remaining stubble, shadowing is minimized and crop penetration is improved. Although the 04 (orange bar on Fig. 1) and 02 (red bar on Fig. 1) nozzles both produce coarse droplet spectrums, the 02 nozzles produce a wide span of droplets better suited to smaller grass targets and achieve better vertical droplet capture. Below you can see examples of the 04 droplet spectrum on the right hand side being relatively large in comparison to the droplet spectrum provided by the 2 x 02 nozzles on the left. The important thing to recognize is that the water volume of 2 x 02 nozzles and 1 x 04 nozzle are exactly the same, however if we halve the size of some of the bigger droplets produced the 04 nozzle we can create up to eight times more droplets with the same water volume.
½ Drop Size = 8 x amount of droplets
Larger nozzle orifices (as present in an 04 nozzle) often have larger droplets which retain speed and energy. While this can be very good for penetrating canopies and broadleaf targets, they are not ideal for small vertical grass targets. The results that you see in Fig. 1 in either the red or blue bar indicate that 250mm nozzle spacings, improve coverage resulting in better kill.
Smaller droplets provide better vertical capture. Larger droplets provide better penetration
To achieve the best results with 250mm nozzle spacings, Croplands use air operated nozzle switching, known as Air Pro - a system allows for three tiered spraying. As the boom spray takes off from the corner of the paddock Air Pro will switch to the smallest nozzle at 500mm spacings. As speed increases, to maintain optimum pressure range the next nozzle size will be selected and switched on. Once the ideal speed is reached the third tier is switched on, meaning that all nozzles at 250mm spacings are operating to achieve the optimum penetration and spray coverage.
The Air Pro system also incorporates boom priming and Air Flush for decontamination. Air Flush offers the opportunity to blast the boom lines, eliminating the majority of chemical and boom cleaning agents in the system creating for a simple and effective decontamination process.