Bill Gordon: Just going to have a quick chat about auto section control. Now, that can be arranged in a number of different ways on different machines. If you have traditional plumbing that's feeding a whole boom section, then you're relying on a valve to turn that section on and off. The width at which it's plumbed becomes the width that you can turn on and off in auto section control.

Where we're turning on and off at the nozzle, we get down to individual nozzle control, which reduces overlap and can cut down your chemical bills. In situations where you've got uneven paddocks or irregular shapes, moving from a standard seven-section setup to even individual or one-metre sections can save an extra five to seven percent on your chemical bill by avoiding overdosing.

Section control is one of those options that's really worth considering. The more sections you have, the less overdosing or waste you'll experience in areas you've already covered. When we get down to individual nozzle control, you can achieve even greater precision. It's worth considering the investment.

Bill Gordon: So this particular system here, where we've got the two nozzles fitted, is turned on and off by an air valve connected by this tube to an air solenoid back at the sprayer. This allows us to get almost an instant on and off at the nozzle, and it's very good for switching between the two.

Once you've fitted control at the nozzle, whether it's with an air valve or a solenoid, turning off here allows you to have flow in the line or a return line back to the tank. That can mean the boom is fully primed or charged when we go into the paddock, so you're not waiting for that to happen. It can also, when you have the nozzles off, reduce settling in the line, which helps minimise blockages. So that flexibility of having a valve like that or an electric solenoid to control this particular system can be very useful.

Bill Gordon: It's very common on a lot of trailing rigs to have a pressure gauge located near the front of the machine, where they're reading pressure close to the manifold. The only problem with that is it's not really representative of the pressure that's going on in the line back on the spray rig. If you actually measure pressure in the spray line, you might find it's quite different to what you're reading here, particularly near the extremities of the boom.

So I try and look at a remote pressure sensor in the line near the back if you want to read accurate pressure or read pressure in the spray line itself. You can then remark this gauge up here to make sure it's reading accurately if you want to know what pressure is going on through the nozzle. This is really important for knowing what droplet size you're producing.

Bill Gordon: Ok, this is a trailing rig fitted with a diaphragm pump. You can actually see the piston heads here. This may look like a large pump, it's quite a big size. We want to read the tag – it only does 250 litres in a minute. When you compare that to a hydraulically driven centrifugal pump or a snail shell sort of design about that big, some of them will punch out up to 800 litres a minute, but some of them in the same size will only do 150 litres a minute, so the tag is very important.

When I look at this particular one, this diaphragm pump, what we call positive displacement. When it shifts the liquid, all of it has to go somewhere. So if I look at a 36-metre boom at the back of this sprayer and say, well, that's 72 nozzles. If they're doing a litre a minute, then seventy litres a minute are going to the boom. If this was operating at full capacity, that's only leaving me, what, about a hundred and forty litres to return to the tank if everything is operating at full capacity.

This machine has a six-and-a-half-thousand-litre tank, and ideally, we want to shift about two to three percent of that volume per minute. In other words, we want to turn over the whole tank volume within 15 or 20 minutes. So we start at six and a half thousand litres, that's 3 litres in a hundred or 30 in a thousand, and six and a half times that. My rough math says about 200 litres a minute is required for agitation. Now, if the boom is taking 70 litres a minute, even with a lilac nozzle, we're not returning enough volume to the tank.

This pump is probably a little bit under capacity for this size tank, and the thing we need to be aware of is that these diaphragm pumps will lose about three percent capacity each year. So if it's six or seven years old, it might have lost twenty percent of that capacity, and the agitation is going to get worse over time. So when we think about the chemicals we're putting in the tank, make sure we've got enough capacity in the pump so we can turn over the volume.

So if you're ordering a new sprayer and you're going to a larger tank to get more productive, think a lot about the pump and the capacity that it has. So what you're putting out the boom, what's left will go through the tank. But think about how it's going to perform in five or ten years because that capacity will go down.

Bill Gordon: I'm standing in front of a trailing rig. This particular machine is plumbed into five sections. Now, we can trace the hoses, but I can also see that there are five control valves up here, one for each section. These are manually switched on and off in the cab. Because it's a 36-metre boom, we're looking at somewhere between five and seven-metre sections. We have one in the centre here, another one as we're plumbing out, plumbed as a single section all the way out to here, and then the final section feeding to this point.

Now, if I wanted to convert this to auto section control, I'd probably have to dramatically change the plumbing. With just five sections, turning on and off a six-metre section would lose some of the benefits of trying to run auto section control. The more sections we can plumb in, the more precise we can get it, and the higher the savings would be.

Graham Betts: We're on the Matrosses' property near Maitland in South Australia, and originally the sprayer was plumbed at 20-inch nozzle spacing and poly plumbing. We've chosen to go stainless steel for two reasons: it's easy to mount and also it doesn't have decontamination issues as much as poly. The other thing we've chosen to do is match the nozzle spacing to the crop row width, and in this case, it's 15 inches. The Matrosses have chosen to go with the Seletron system. What this gives them is the flexibility to have every nozzle body turn on and off, and every nozzle body is virtually a boom section.

Also, to give nozzle choice a bit more flexibility, they put the triples on to give them a three-nozzle option. The other thing we took advantage of is to install boom recirculation. What we do is feed the liquid into one end of the boom section and, obviously, we've got this fitting on the other end of the boom section. This gives us the ability to remove the fitting there and flush the line out, or while they're spraying, they can have boom recirculation happening.

On the end of this line at the top of the tank is a boom valve, and when the master switch is turned off, the liquid goes through there. So we're having no residue issues. Also, the other benefit of this is we can prime the lines with chemical and don't have to flush the whole boom out. There's no need to waste 100-150 litres to flush the lines.