One of the most overlooked items in the calibration process and especially in boom sprayers is how the nozzles are aimed.

Generally, we just point them directly downwards or at right angles to the plant (in the case of laterals) and expect the fog they produce to travel in and out of the canopy and cover all the foliage on both sides.

If we make a big enough fog, this will be very true, but constraints on the amount of fog we can make in the future (drift) are going to cut into the efficiency of our coverage, which we took for granted, until now.

Aiming the nozzles so that their pattern penetrates the canopy will greatly improve our coverage and reduce drift. However, we cannot follow a rule-of-thumb on this except to try to get the spray to drive into the plants as low as possible at an angle which will make it "bounce upwards" and travel to most of the areas of the canopy, without producing great amounts of drifting fog.

Each crop has to be looked at with that in mind: how to get the spray down into the canopy before it becomes a fog.

One approach is to use narrow angle nozzles. These would be spaced closer to each other on the boom to make up for the loss of pattern produced by the wider angle nozzles, and the narrow pattern will propel the spray deeper into the canopy, especially if it is aimed forward at an angle of 35 degrees or less to horizontal.

The narrower pattern will travel farther before it begins to "break-up’ and, if you regulate your boom height accordingly, you should notice practically no drift or fogging above the canopy.

Putting more nozzles on the boom because of closer spacing will require you to use smaller orifices to maintain the volume. This you can calculate and calibrate yourself.

In order for this to work, you must use Disc/Core type nozzles. Get away from the Teejet type fan nozzles, they are for herbicides and banding, not for under-leaf coverage. The disc/core nozzles will give you angles as small as 15 degrees. (you have been used to 80 to 90 degree angles until now.)

We are giving you the basic idea and what to look for. It’s up to you to decide how you want to aim your nozzles, but please give it some thought.