This video appears in modules 2 and 10.

Bill Gordon: We're looking at weather monitoring in the field for when we're spraying, so I've got a handheld weather meter here. This will tell me things like temperature, humidity, wind speed, and when we're recording these things in the paddock, it's a legal requirement to measure those at the site of application, so a portable meter like this is really handy.

When measuring wind speed, that should be done at about 2 metres in the air. That's the height at which they measure wind speed to judge or calculate the no spray zones or downwind buffers on the label. The other things I need to measure are temperature and relative humidity. That should be done at 1.25 metres and ideally, these little sensors would be shaded, so we don't want to get direct radiation on them. I'd probably turn that away from the sun while I'm doing temperature and humidity, and I need to record those measurements—wind speed, wind direction, temperature, humidity—and generally every load, so with the start of the day, each load and at the end, and I need to make a record of them.

If I'm going to make a decision about whether I keep spraying or not, particularly based on temperature and humidity or delta T. I also want to take a measurement at the target, so I'll take my handheld weather metre and I'll place it down in amongst the weeds or the crop canopy. Because I've got soil moisture or the plants aren't stressed, quite often the humidity will be lower down there, or the droplet survival will be better.

So handheld weather metres are a really useful tool for recording those things out in the paddock, but if I'm going to make a decision about whether I keep spraying as it gets to higher temperatures, I'll measure it down at the target.

This video appears in modules 4 and 21.

Bill Gordon: We're looking at assessing spray deposition in stubble, particularly in summer time because one of the issues we have on most machines is problems in the wheel tracks and issues with dusting around the wheels, so what we've been doing is positioning water sensitive paper down in amongst the stubble, but also in the inter-row. It's important to have a reference point when you do that, so when checking across the machine we'll start out on the boom and see what the deposition should be without interference, and then we'll come back into the machine.

So what we'll do is check some deposition in the standing stubble out on the boom here. Okay we're about the midpoint of the boom out from the machine, and we placed the cards in the inter-row or between the standing stubble but also at the base and what we're looking for is comparing the deposition between the two areas, so looking at where the droplets have landed, seeing if there's enough coverage there we're going to use this as a reference point. The things we're looking for on this water sensitive paper or card is how even that is between the two. If we get to the point where these are pretty even it's a great reference point, so on this we can see fairly uniform droplets, you actually use the core spectrum here at about 80 litres of water and the two cards look very similar.

Now we can use at base programs like snap card to actually measure that deposition as a percentage coverage and we can see how close it is, cos quite often with the naked eye they'll look similar but you might not pick up the subtle differences, but these two to me look pretty even and they'll form our reference point for comparing the other cards in closer to the machine, so whatever happens here out on the boom we'll be comparing other parts of the boom particularly around the wheel tracks in the center of the machine to see if it is as good as it is here. Now if we see any issues between these, like differences between what's happening in the inter-row and the stubble line, particularly reductions in the stubble, that should be a cue to us that we need to change something either volume or pressure, maybe manipulate droplet size a little bit, so this is our reference point. If we get this right across the boom then we can go and have a look at the center and see if there's anything also we need to adjust to tweak the wheel tracks or manipulate for dust.

We're moving into the wheel track area of the machine now and it's really important focus for summer fallow spraying, not only for dust but looking at what's going on around the wheel track, so we're looking at either outside the wheel or inside the wheel and coming down to the cards, this one placed on the outside of the tyre, so we're comparing what's going on in the inter-row to the standing stubble and I can see in the standing stubble on the outside of the tyre the deposition is quite a bit lower on this card. If I come to the inside of the tyre over here, again if we look at what's going on here in the standing stubble you can see the deposition is a lot less there in the standing stubble, so what we're going to do is have a look at the setup on the machine, see where the nozzles are and see if we can make some improvements.

We come in to look at the nozzle setup on this machine, I can see it's a dual boom and that in and around the wheel itself they've actually got a larger nozzle on here to increase the flow rate, which is very common for most operators, they'll increase the flow on the wheel to try and deal with dust and wheeltrack issues, but what we've seen is that the problem is actually also on the outside of the wheel, so rather than just increasing the flow rate in one spot by in this case including a bigger nozzle, what we should do is probably spread that flow, at least look at outside of either side of the wheel to try and even up that deposition and then run those tests again to see how well we've done.

Once we've done that we can look at other areas on the machine, so while we're doing the same test, I tend to not only focus on the outside of the boom or in the wheel tracks, I'll take a measurement in the center on these particular wheels inside and outside on the other wheel and also out on the center of the boom and make the same comparisons. Remembering that our reference point is what's going on out in the boom, if we see any differences in the center around the wheels this is where we're trying to improve things to get our fallow spraying to be a little bit better.

Bill Gordon: Behind me is a single row of casuarinas. They're quite tall, and as you look behind me you'll see there is approximately fifty percent light and dark as you look through them. That's the best indicator of porosity or the amount of airflow you can get through the trees. The thicker that canopy is, the taller they need to be to compensate. So with this sort of porosity or amount of light and dark, you need to be about one and a half times the release height of the spray.

One of the great things about casuarinas is that, because they're drought-adapted, they tend to have a thick, waxy cuticle, which helps resist the uptake of chemicals. This means if you plant a species like this in a vegetative barrier, they're more likely to survive and keep doing the job they're designed for, which is to filter the droplets out of the air.

Bill Gordon: Many people would have heard of the term DRT or drift reduction technology. From a grower's point of view these are the things that allow us to minimize the amount of product or droplets of that might get into the air while we're spraying. The things that can help reduce drift are things like boom heights, so lowering the boom height as low as practical when you're operating, but still maintaining double overlap
that's one way of cutting down how much product could get in the air.

Another thing that you could do is with your nozzle selection, so choosing nozzles with larger droplets or coarser spray qualities also reduces drift potential. There's other things as an operator you may be able to do for instance your formulation choice or the addition of adjuvants to the tank may also affect droplet size which could cut down drift and all these things when reduced drift reduce the amount of product that can move down wind or away from this sprayer.

When it comes to the APVMA - the guys that aprove products for sale and determine what goes on the label, DRT or drift reduction technologies have a very specific meaning, so on the label there will be approved DRTs which will allow growers to potentially reduce their no spray zone or that downwind buffer distance that's required for some products. The things that may be acceptable on the label in reducing a buffer may be operating at reduced wind speeds, again lower boom heights or changing droplet size. They will also recognize certain formulations as reducing drift.

So from a growers point of view it's always important to check the label and see what technologies or drift reduction technologies will be acceptable if you're looking at reducing a no spray zone.

This video appears in modules 4 and 10.

Bill Gordon: One of the things we can utilise when we're spraying is the visual clues and things happening around us, and certainly clouds are a great indicator of what's going on. When we see fluffy clouds—the cumulus ones that start to form in the morning—that means the inversion is generally broken up to about that level. Later in the day, they're also a good indicator of the onset of an afternoon inversion. So when we look at those clouds and they start flattening out on the ends, particularly in the distance, I'd expect we've probably only got another 20 or 30 minutes before the wind speed tends to drop off.

When the sun gets below about 20 degrees, the clouds are flattening out, and the wind speed drops, it becomes very dangerous for spraying because we can't predict what's happening. So, using visual clues as well as monitoring the weather is very important for spraying operations.