MSU Extension Irrigation

Hello, my name's Lyndon Kelley. I work for Michigan State University and Purdue Extension on irrigation issues. Today we're talking about some of the label requirements for chemigation purposes. You can find additional materials on chemigation and other safety factors when using pesticides within a pivot at the Ag Engineering site at Purdue or Michigan State University or MSU Extension Service at Michigan State University. Today we're drawing information from the chemigation labels from either Headline AMP or Trivapro. These are fungicides commonly used for tar spot have been in the press recently. But remember, that we have to have a chemigation label on whatever products that we're putting through the pivot to be legal. And remember, that's part of the whole label requirement, that three-legged stool that we talk about, as far as labels being in agreement between the registrant, the Environmental Protection Agency, and the applicator, that's you, to make sure that this is a safe and effective use of the pesticide. The purpose of these pesticides is that they coat the leaf with a fungicide that decreases the rate of growth of or inhibits the rate of growth of a disease. There are some side benefits to like the Headline AMP label that has actually a growth-promoting effect. Those happen if we can get the concentrations, of the pesticide, high enough in almost a half an inch of water per application. But, for most parts we're looking at the fungicide application with these two products. And, to protect the leaf from a foliar disease say-- such as a TAR spot, we need to get a high enough concentration. We do that by keeping the amount of water application pretty low. So if we look at the Trivapro label, they'd like to see a tenth of an inch to no more than a quarter of an inch per acre for the highest effectiveness. And then, there's actually some more warnings given here that they may not be effective if we're at higher levels or un-uniform levels. Because this is actually coating the surface, it really doesn't do any good to put this product through subsurface drip, drip, drip or trickle irrigation or flood irrigation, because we're not coating the leaves. So we need a pivot that can move pretty fast. The way you know if your pivot is capable of doing of these applications that fast is to look at the application chart. The application chart at 100% would be the fastest or the smallest application the machine can go at. If we look at the upper right corner, this machine is capable of putting on 1700. So it's right in the middle of the recommendation for the fungicide we're talking about using 1700 at 100%. But, the application chart for the machine at the lower left, little older machine, it's capable of putting on three-tenths as the smallest application; it can make three-tenths at 100%. So it's actually quite a bit of a product that is going to wash off the leaves and not be effective. We know that machines designed for this purpose are being designed to put on seven hundredths, so less than a tenth of an inch because that's what we believe is effective, or the ability to hold about seven hundredths of an inch of overhead application water in the foilage at tassel or after is pretty commonly accepted. So the labels that we look at, the Trivapro says that we need to watch our wind direction so we're not making applications out of the field. That's a law, or requirement within the Indiana and Michigan pesticide regulations that the pesticide not leave the field. That's also on the GAAMP requirements in Michigan. But, what we see probably more common than wind drift is actual off target from end guns. And these are machines that probably should not be used for the purpose that we're looking at for today. A good effective application of water will mean we'll also get a good and effective application of pesticides, in this case, fungicide through our chemigation system. There's some words of warning here in the Headline AMP label it actually says you may have crop injury, lack of effectiveness or illegal pesticide residue in the crop if you have a non- uniform distribution. And then, in the Trivapro label, it actually says somewhat the same but also adds, do not use the end gun when chemigating with Trivapro fungicide. So within this label, they've actually ruled out the use of the end guns. And, in the lower right picture is a good example where maybe that would be a little bit more than you could tolerate. You may choose a pesticide based on whether you can use your end gun or not. So the starting point at a good uniform application is the repair of leaks and other parts of the machine that would potentially cause more water in one area than another. So here we have a water supply at the stem in the upper left corner. Flange that needs repaired in upper right corner. In the center we've got a missing sprinkler, giving us that fountain of youth look. We already talked about watering the road. That's usually an issue of maintaining the control system on the end gun. And then, last but not least, a little harder to see until you understand a little bit more about it, but the cornering arm on this machine is all folded back, so it's all traveling over the same portion that's already been watered and every one of the sprinklers are on and the end gun. So this makes a tremendous over application and is an issue of maintaining the control system that regulates the on and off on those additional areas when the machine is folded back. The next thing we need to think about after we got all the repairs is that we have a uniform application. We've done a lot of work over the years and there's a number of a system for putting those together and graphing those. In the graph, here you have a dot. Each of those dots represents a Taco Bell cup. You see the picture in the lower right. In a perfect world, every Taco Bell cup from the center pivot point to the nth row of the, furthest row of the end gun should be the same. In a perfect world, we don't do that, but our most of our equipment should be capable of about plus or minus 10%. So if I thought I was putting on an inch, most of the field should have between nine-tenths and 1.1. inches. A typical problems that we have, yes, we have some sprinklers or something missing and you can see one at 220 feet. And again, at the seventh tower where we have lows and then highs. But, a lot of times the greatest impact as far as acreage is on the end gun. So straightening out or correcting those end gun is a important thing before we think about using chemigation. Some of you would say, well at this point, well is my machine really capable of getting that fast of an application and that uniform? Well, sort of what we consider to be the minimum, the speed we've already talked about. It needs to be able to cape a little to get below that two-tenths of an inch or somewhere in that range, 85% or better on the Christiansen's coefficients of uniformity would be ideal. There's a number of pivots that have been tested by the Michigan Environmental Assurance Program and by the conservation districts in both Michigan and Indiana. If you have those tests and things have been kept up since, you're probably in good shape. If you don't have those tests, you probably ought to look at everything being repaired and that the sprinkler package is within 10% of the pressure on the sprinkler package specifications. So if it says it's supposed to have 30 pounds of pressure on the at the center point. As long as we're within 27 to 33 pounds, we're probably in good shape. If we're above or below that, then we know that there's something wrong with the supply going to the sprinklers. We're going to talk about the required backflow protection that's needed. Major repairs. We talked about we'd like to make sure we don't have any runoff issues that we aren't applying water faster than it can go into the soil and that we're not having water that has a pesticide in it leave the field. We'd like to see a minimum of areas that are double irrigated where two pivots are covering the same area. So we'd like to shut end guns off where we have those double covered areas. And then, we're going to talk a little about interlock systems for safety. The main component for safety is this backflow chemigation valve. Its purpose is to make sure that once we've mixed the pesticide with the water, it does not seek its way back to its source, the pond, river, stream, or well that it came from. That's very important for producers to protect the environment, but especially important when we think about this is also the water source that your family and employees drink from. So, this chemigation valve is different than a backflow valve. They both share the same floppy valve. Spring loaded 5-pound spring flop valve. But, the chemigation valve has an added component that relieves the air vacuum created when the well shuts down. This drains that cavity between the flop valve and the water source. So, that's done with a floating ball. The top of the component as the water fills when the pump comes on, it seals that off. When the pumps shut off, the floating ball drops down allowing air to come in. And, we'll hear the huge vacuum suck air, [whoosh] you'll see. And then, we actually want to drain that, that section between, behind the floating ball and the flop valve. And, we do that with that lowered drain valve, which is also set at five pounds. It's important to remember there's an inspection port designed into these. Before we start any chemigation process, we want to depressurize the system, open up that chamber, and reach in and make sure there's no debris or anything clogging the valve. We usually know this pretty quick because when we shut the system down, the drain would be running continuously. A few of you may be using water sources that are also shared with the human public or with the human-- human homes or other things. It's important to remember that anytime we're using a irrigation system with public water supplies that we need to be using a RPZ reduce pressure zone valve. This is written into both Mi-- Michigan and Indiana's well code. The only alternative to these systems where we're irrigating or using the public water as your water supply is to use a makeup tank or a supply tank that is not directly hooked to the water supply and has an air gap. So, the air gap needs to be six inches or twice the diameter of the fill pipe from the upper portion of the tank. So there's no chance that the tank can be overfilled and sucked back to the water supply. So, this air system is the only alternative to the reduced pressure zone valve if you're using water from public water supply. Also, an important factor in protection of groundwater is the concept of interlocking. And, all of our pesticide labels are requiring interlocking of systems. Center pivots lend themselves very well to this industry for a long time, has had designs that allow the center pivot itself to shut off the water supply, both for electric pumps and diesel pumps. A little more complicated with diesels. These systems can be then upgraded. When we add the injection pump so that if the injection pump shuts off, it shuts off the well and the center pivot. If the water supply shuts off, it shuts off the center pivot and the injection pump and vice versa, so that basically everything's tied together so that if one component goes down, they all go down safely. This prevents contamination to the groundwater. It also protects over application onto fields and greatly improves our ability to safely and effectively use the pesticide. New to some of the chemigation valve labels that are there is a solenoid valve added into the system. Some of our older equipment will need to be updated to meet this requirement. What they're asking for is a normally closed solenoid valves. So, when there's no electricity going to it, it's closed between the injection pump and the supply tank. What this is gonna do is it's not going to open up the supply from our chemical tank until the electricity's on and the pump is pumping. If the electricity shuts off to the pump, it's going to shut that solenoid off. So it's going to cut off the pressure from the supply tank to the pump when the pump isn't running. So that's a requirement now in many of the fungicide labels. So, some of you are going to decide at this point that applying the chem-- the fungicide through a chemigation system or through irrigation may not be all that effective. But, there's still some things we can do with out pivot to not increase the disease potential. Many of our foliar diseases are exasperated or increased by the number of times that we irrigate or when we irrigate. If you look at the first two green arrows on this chart, this is a leaf wetness chart. Lower one is the lower third of the canopy and top chart is the top third of the canopy. If you notice the first two irrigations, are marked by the green arrows did not increase the amount of time it was wetted. Less than two hours. And we know tar spot, it takes about seven hours to further the disease in progression. But, if you look at the third application, that application went on in the evening and caused eight hours of wetted time period. So, it did increase the potential for disease. Notice several of the rainfalls also got into the time period where they were greater than the seven hours. It'd be ideal to be able to irrigate only during the morning and afternoon so that the crop could dry off. But, this would take a lot more water capacity than most of us have. Most of us are designed to run 24 hours a day during the peak uses of water. But, this would, may be a potential for someone who has a diseased area in the field, make sure you're watering that in the morning or early afternoon so it dries off before the wetted period or the dew period in the evening. Making sure that the irrigation is actually beneficial is another way of minimizing the increase in irrigation related disease potential. There's good information that comes from Michigan State University or Purdue Extension. Or now, the National Weather Service are all publishing data on reference ET. Corn from tassel through early dent uses a 115% of reference ET. And then, each application we lose the first 10% to the foliage and upper surface. So we do those multiplications. If I had a reference ET for the weak of 1.2 inches, that's how much grass would need-- I would need to apply 1.65 inches to keep up with that. Applying more than that, just increases disease potential. Less than that, we're drawing from a reserve and may increase yield lost to drought. So we've determined that we do need to irrigate. But now, how much do we put on per application? This is an excellent way of controlling our risk for foliar diseases. If we have that typical August and we need to apply three, 3.1 or three inches of water to add to that typical August 3.2 inches of rainfall, that three inches of water could be put on in as little as three, one inch applications. In other words, wetting the leaves only three times. And...or it could be put on as many as 12 quarter-inch applications, wetting leaves 12 times. So you'd have four times more wetting events and exposure to increase our disease. Important also here is that you get more effective water when you use larger applications because the first tenth of an inch or so of each irrigation or overhead application, is tied up in the foliage and the upper surface. So we get more effective water and less disease potential Not everyone can do this because some of our pivots supply water faster than the soil can take it in. And we need to do small applications, but try to keep your applications up to the greatest amount that you can use, within reason, inch, inch and a quarter, as long as we don't have runoff issues. So that's what we have for today as far as information on chemigation and fertigation and safety aspects and how to reduce potential disease progression from irrigation. If you have any questions, please give me a call or email me. I'd be glad to help. Have a good day.