Episode 10 - Getting Sprayers into Tip-Top Shape for 2020

Arkansas Row Crops Radio, providing up to date information and timely recommendations on row crop production in Arkansas.

Tommy Butts: Welcome to Arkansas Row Crops Radio. My name is Tommy Butts, Extension Lead Scientist for the University of Arkansas System Division of Agriculture. And joining me today is Jason Davis, Application Technologist for the University of Arkansas System Division of Agriculture. 

Today wed like to discuss with you a few ways in which we can get our spray equipment into tip-top shape to improve the safety, accuracy, and effectiveness of our pesticide applications. So, burndowns are really gearing up across the state. Some have already went out but there are many more applications to come for the 2020 growing season. And with some of the weather forecast here in the near future with a lot of the rain that's coming, we figured it was a good time to discuss some of these spray equipment safety and equipment checks so that we can take care of it during this rainy period before our season really kicks into high gear. 

So, the first thing that we wanted to discuss was to basically do a very thorough inspection of all sprayer parts. So, that includes the spray tank, hoses, connections, the spray boom, nozzles, everything. So, we wanna be able to check for leaks, obstructions, cracks, all those kinds of things. And if we see any of these issues arise, immediately correct those situations so we don't have problems in the fields when were trying to make our spray applications. Another thing that we can check over and make sure are in operational condition are filters throughout the spray system. So, we wanna make sure that those filters are cleaned and installed, and we also want to make sure that there are no major holes or cracks that can allow large pieces of debris to flow through the spray system. So, if we have any issues with those filters, those should be replaced as well and make sure that they're in great operational condition. 

The next thing that we should look over are any of our electronics, and especially the wiring harnesses to make sure that there's no disconnections, that everything is in operational order there. And then also, just that we didn't have a mouse or something get into the system over the winter and chew through one of our wires causing us to not be able to use our electronics. So, we've seen it several different times and its one of those things that if we can correct now, it's not too big of a deal but if we get out into the field and all of a sudden, our electronics aren't working it could be a big issue and cause us some pretty big delays, especially when ya know, most of our pesticide applications are pretty timely. So, making sure to check that that's all working ahead of time can be a pretty big positive as well. 

One of the other things that we wanted to be able to look at and investigate before we get into the field too far is to check the size of our spray tank. And so, the reason this comes into play is most of the time we assume that those markings on the side of the tank are fairly accurate, and in reality, we found that those markings can be pretty far off from what that tank is actually going to hold. And so, there's actually been some research that's come out of the Midwest where they investigated a few different spray tanks and what their markings said versus what they actually held. So, for one example one spray tank they measured was marked for 1000 gallons, they used a flow meter to measure how much water actually went into the tank when they filled it to that 1000-gallon marker, and it actually only held 950 gallons. 

Well, there's 2 problems with that, we're off by about 50 gallons on what we thought was in that tank. So, the first problem with that is if we're spraying at say 10 gallons per acre, were assuming with 1000 gallons we can cover 100 acres. Well, we actually only had 950 gallons in the tank so we can only cover 95 acres. So, we've lost efficiency there. We now have to remix, we have to cover that 5 acres or ya know, something else. Maybe we don't end up spraying that and we get weeds that end up taking up that 5 acres, so that's not good. The other issue is that we're applying more active ingredient product per acre there because we mixed for 1000 gallons but we only actually had 950. So, if we're applying more product per acre, we could lead to some crop injury concerns, maybe carry over concerns for the next year, some other issues like that. So just because we didn't know how much actual water was in the tank, we could see some crop injury problems. 

Now on the opposite side, they also had an example where they measured a tank, it was marked 750, they filled it up to that line, the 750 line, and what it actually held was 875 gallons. So, that's 125 gallons off. Now, the problem with that situation is that were actually applying less active product per acre. So, there's more water in there then we mixed for, which means our product is more diluted and so with that less product per acre we could actually see things like loss of weed control because were applying a lower rate, or actually contributing to herbicide resistance development or other pesticide-resistant development simply because we applied a lower use rate then what is actually labeled. So, there's some real instances here where we need to make sure that we have what is actually marked in that tank. 

Now, the first thing that I always like to tell you to look at just to see if you think your spray tank markings are correct or not is to just look at the spacing between markings. So, if you have a round or an oval tank, your marking should not be equally spaced going up the side of the tank. If your markings are equally spaced on a round or oval tank, they're wrong. There's no if, and, or buts about it, they're wrong because if you're on a round or oval spray tank, you have more volume in the middle of that tank and your markings should be closer together, they should have less space between them. If you get to the top or the bottom of that spray tank, there's less volume in those areas and your markings should have farther spacings between them, bigger spacings between them. So, if you have a round or oval tank and those markings are equally spaced, it'sits automatically wrong. And so, we can automatically assume then and make the corrections we need to for that spray tank. 

So, there's a couple different ways that we can make these corrections. One would be simply through weighing the sprayer. So, we would want to weigh the sprayer completely empty, record that down, then we can go backfill up our spray tank to our designated line, say its 1000 gallons, we fill it up to that 1000-gallon line. Then we go back and we weigh the sprayer again, now water weighs about 8.34 lbs. per gallon. So, if we go back and we filled it to 1000 gallons, our sprayer should now weigh 8,340 more lbs. then it did when it was empty. Now, the other way that we can do this and the way that I like to do and think is a little bit more accurate is to use a flow meter. Now the first thing that we need to do with a flow meter is make sure that it is calibrated but if our flow meter is calibrated, we can take that and actually mark different amounts all the way up our spray tank, and so then that would help us if we're doing different size loads. So ya know, maybe a quarter load, a half load, a three-quarter load will have a specific marking on our tank for each one of those. So, when we use that flow meter maybe we fill it up to 250 gallons and we can mark on the outside of the tank with a sharpie. Then we go to 500 gallons, 750, and then finally the 1000 gallons and we have accurate marks of how much that spray tank holds and where those lines are on that tank. So, this can be a really big deal, we've had numerous instances like I mentioned that have popped up and had either losses in control or maybe more crop injury due to these tank markings just simply being incorrect. And so, during these rainy-day periods,, it can be an excellent way to improve the overall effectiveness of our applications. Now, after we've done all those other checks for any leaks and obstructions, our filters, electronics, and the size of our tank, and we've made any necessary corrections, the last thing we should check and probably one of the most important things that we need to check are the nozzles that we have on the spray boom. 

So, first things that we should check is making sure that there are no obstructions on any of the nozzles, there's no exit or phystamformaty and they're forming a good spray pattern that we expect for the type of nozzle that we have on our sprayer. Making sure that all that's inadequate condition is pretty important, and if any of that is not the case then we need to replace those nozzles immediately. Finally, along with those nozzles checking for obstructions or any deformities, we want to check to make sure they're not wore out. So, the best way to check to see how wore those nozzles are is to do a flow rate test. And for this, I will turn it over to Jason Davis, and he'll give you some information on checking for our flow rates out of our nozzles and then a few other details as well so take it away, Jason. 

Jason Davis: Thanks Tommy. Ya know, most ground applications in Arkansas and the Delta are made with electronically rate control equipment, which means that as the equipment speed increases or decreases, flow to the boom automatically increases or decreases to maintain spray volume. And this leads a lot of applicators to assume that they're automatically calibrated or that their nozzles are in pretty good shape, and unfortunately this isn't always the case. Our spray monitors do a pretty good job of managing flow to the entire boom but they are limited. They assume that product is distributed evenly throughout sections and between nozzles, and so as nozzles wear this even distribution can be compromised and lead to both pressure and flow discrepancies. Although, traditional calibration procedures are not necessary, with rate-controlled systems, a nozzle catch test and a pressure test is important to ensure an even distribution throughout all nozzles. So, this nozzle pressure test should be completed at least annually as part of troubleshooting kind of like we're discussing today and anytime modifications are made to the field computer or equipment just to verify that the information on your screen is accurate. 

So, step 1 you need to verify your pressure. Because the plumbing of our modern spray equipment is pretty complex, the product as its pumped through the system often has an appreciable amount of pressure drop and so when doing a nozzle test, its really important to get an accurate pressure reading at the nozzle. The easiest way to do this is by assembling a pressure gauge that can be quickly and easily mounted onto a nozzle body. So just put together a pressure gauge ya know, with a quarter-inch threads and do a quick connect nozzle cap with quarter inch feambell threads that fit your t-jet or wilger nozzle bodies. Most the time these parts are pretty easy to find at most AgRetail stores, and in the context of this conversation, a nozzle mounted pressure gauge is the only way I'd recommend to do your nozzle testing. 

The next step is to confirm your flow rate and so a nozzle catch test will confirm the even distribution of flow across a boom by identifying worn, damaged, or plugged nozzles. And so, identifying these worn nozzles is pretty easily completed by comparing a nozzles measured flow to what its rated to flow or its design flow. And so, a nozzle flow rate or its designed flow is measured in tenths of a gallon per minute at a standard measured 40 psi and these flow rates are listed on the nozzles nomenclature. So, for example, if you've got a 11004 or a 10004 that nozzle is rated at .4 gallons per minute measured at that standard 40 psi. And so, at the end of the test, you would compare the output of the nozzles that you measure with this designed flow. 

So, lets talk about taking the actual measurement. So first off, as Tommy already mentioned, be sure to have clean strainers, make sure your tips are cleaned to ensure an accurate flow measurement, you're going to add just water to your spray tank, it's gonna be pretty important to make sure there's not a lot of foaming going on so if you've got antifreeze in your tank get it flushed out properly. We want to again, set the boom pressure to 40 psi and we wanna confirm that pressure at the nozzle using that assembly I mentioned earlier, so not on the pressure transducer up the system. Use a stopwatch and a container measuring in ounces or milliliters to carefully catch the flow from each nozzle for one minute. Another handy tool is to use a spot-on spray calibrator, makes this job much faster and easier. Typically, you can get a gallons per minute reading for nozzle in just a few seconds instead of minutes. And so, since it's important to measure each nozzle multiple times, to check for consistency, that's a pretty handy tool, and I'll talk about how you can get access to one of those here in second. If you're measuring in ounces or milliliters per minute be sure to convert that over to gallons per minute. The next step is to compare your measured gallons per minute flow from each of the nozzles to that design flow that we mentioned earlier. Design flow is again the last two numbers stamped on the nozzle and so nozzles should be discarded if there is a measured flow of 10% of the design flow or higher. So, in our example, if the design flow was to put out .4 gallons per minutes at 40 psi, 10% overflow would be .44 and so an easy rule of thumb to remember is that if you're measuring flow at 40 psi when you calculate or measure a double-digit flow rate or higher relative to design flow, you need to replace that nozzle. If several nozzles are worn out throughout the system, its recommended to replace all the nozzles on the boom. And so, these procedures are equivalent to the calibration of just a standard speed pressure system and again recommended to be completed as part of regular equipment maintenance. This test can also be performed on any pulse with modulated sprayer simply by turning the duty cycle to 100% and then again finding that 40 psi to do your test measured at the boom. 

It's worth mentioning that in every county in the state, the county extension office has a sprayer calibration kit that we've put together that includes all of the necessary tools to perform this test. In these kits, it includes the handy spot on spray calibrator that I mentioned earlier as well as the pressure gauge assembly that should fit your sprayer. So, be sure to contact your county agent because they're going to be more than happy to come out and help you do the nozzle testing, or provide access to the kit for you to do on your own. So be sure to go visit with them before the season gets kicked off. 

Tommy Butts: Thanks a lot, Jason. And thank you for joining us today and learning more about sprayer equipment and checkups, and hopefully improving our pesticide applications for the 2020 growing season. As always, thanks for joining us on Arkansas Row Crops Radio. 

Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information please contact your local county extension agent or visit uaex.edu