A 2,000 L mist blower moves a lot of air. That is the point of the machine, and also the reason most calibration problems start with it. If the air stream is stronger than the canopy can absorb, the spray leaves the far side of the tree and lands on the next row or on the drive.
Set the air before you set the pressure
Start with the blower at half throttle and the deflectors angled at the lower third of the canopy. Walk 20 m downwind and watch the drift. If the spray plume is still visible above head height, reduce air volume or open the top deflector. Repeat at full working throttle once the shape is right.
- Air volume carries the droplets; pressure only breaks them up.
- Match the air outlet height to the fruit zone, not to the tree height.
- Reduce air on the upwind pass, increase on the downwind pass, never the reverse.
Reading the deposit
Water-sensitive cards placed at three heights on the near and far side of a tree tell you more than any pressure gauge. A good pattern shows medium coverage on the outside leaves and a light film on the inner ones. Saturated cards on the near side with dry cards on the far side mean the air is too strong for the volume of water you are applying.
With a 2,000 L tank at 250 L per hectare, a 40 hectare block takes eight fills. Every point of wasted spray is multiplied by that number, which is why an hour spent with cards is the cheapest hour in the season.
The blower does not spray the tree. It delivers the spray to the tree, and that is a different job.
Working with a trailed unit
On a trailed blower, the PTO speed sets the fan and the tractor forward speed sets the dose. Keep the PTO at rated speed and change the forward gear to adjust litres per hectare; slowing the PTO to reduce air also reduces the pump output, and the two effects cancel in a way that is hard to diagnose later.
A worked example: 4 m rows, 5 m trees
Take a block with 4 m rows and trees 5 m tall, canopy 3 m wide. Start with the top deflector closed and the middle one at 30 degrees, fan at two thirds of rated speed and pressure at 12 bar at the head. Walk the row and place cards at 1.5 m, 3 m and 4.5 m on both sides. If the 4.5 m cards are dry, open the top deflector one notch before touching the pressure.
Adjust one variable per pass and write down what changed. Two passes with cards will teach you more about a specific canopy than a season of guessing, and the settings carry over to the same block next year.
The 2,000 L mist blower runs with adjustable deflectors and a two-speed gearbox on the fan. Ask us for the deflector settings that suit your canopy.
