Ag Geek Speak

16. Variable Rating Herbicides with Kyle Okke Pt. 2

• A Podcast for Precision Agriculture Geeks • Season 2 • Episode 16

Share episode

We sit down (again) with Kyle Okke of Agile Agronomy and explore how to make variable-rate residual herbicides actually work, from nozzle physics to dual-tank setups, and why agronomy must lead every tech decision. We also talk PWM (pulse width modulation), drift control, and mapping weed hot spots for smarter applications.

Additionally...
• Limits of conventional pressure-based rate changes
• Why droplet size, pattern, and drift control matter
• PWM and duty cycle basics
• Turn compensation for consistent coverage
• Mixing residuals with post products without losing efficacy
• DIect injection timing challenges at boom length
• Dual-tank, dual-boom systems for split strategies
• Cost and scale drivers for adoption of certain spray systems
• Green-on-brown paired with variable-rate residuals
• Drone mapping kochia and wild oat patches for targeted residuals
• Reducing passes, resistance pressure, and carryover risk

Stick around for the final part of our discussion, part 3!


https://gktechinc.com/

Sarah:

And now it's time for Ag Geek Speak with GK Technology's, Sarah and Jodi.

Theme Song:

In the fields again. I just can't wait to get in the fields again. The life I love is spread in product for my friends. And I can't wait to get in the fields again. No, I can't wait to get in the fields again.

Jodi:

Welcome back to another episode of Ag Geek Speak. We are in the second part of our conversation with Kyle Okke of Agile Agronomy out of Dickinson, North Dakota. And in the first part of our conversation, we really talked about, you know, what were the circumstances that prompted Kyle to start thinking about and implementing variable rate herbicide applications, specifically residual applications to help reduce crop injury. And now we're getting into the nitty-gritty details of how we actually do this because it's not as simple as just varying your urea rate. There are some other considerations that uh that uh have to be made too. So with that, Kyle, we were just talking about, you know, uh conventional rate controllers and being really cognizant of droplet sizes when you're changing pressure. What is the ideal system like? If how have you made this work? What are you varying? What's been successful? And yeah, tell me more.

Kyle Okke:

Sure. So the last the last time I spoke, I think we kind of cut it off around uh talking about like how conventional spray systems work and and why they don't work that great in in a variable rate spraying application, because you're you're you're going way outside of the parameters of normal operation for spray nozzles when you're doing that. So that the conventional system, even though a variable rate controller does adjust your applied rate through there, nozzles really weren't meant to go through those biggest swings. So so what'll happen, especially in these tank mix scenarios that I was talking about before, where you're having post-emergent and residual products together, which isn't ideal, but we can do it. And there are a lot of nuances in where to make that work. But um if you drop to say like 15 pounds of pressure to get your rate down low enough to reduce injury in these, you know, poor soil areas where you know you're gonna see crop injury, well, you're reducing your tank mix partner too, and you're collapsing your pattern, you're getting way smaller droplets with that lowered pressure, and you're not gonna achieve the post-emergent weed control you're after in those areas versus like going to the areas that receive the high rates. Well, you have the potential for over-pressurizing the system, and now you have a lot of fines, which coverage is fine, but when you produce a lot of fines, you have a lot of off-target movement. And so now you're running the risk of off-target movement. And I'm not just talking like going along a bordering field that maybe has a sensitive crop and you're you know concerned about that. I'm talking about off-target movement where you're trying to apply this applied rate to this very area, and then all of a sudden you get a gust of wind and it pushes a lot of that applied particles that you were trying to get to land to the ground. Now they're not going to the ground. So there's a lot of you can variable rule apply with a conventional system, at least mechanically. Now, agronomically, does it make sense? Like once it leaves the sprayer, that that's where that's where it kind of lacks. So so in enters pulse with modulation.

Sarah:

Okay, before you say pulse with modulation, which is super fun to say for everybody out there, say it with me. Pulse with modulation. That's so fun. Anyway, I want to remember remind everyone that whenever we are doing there, there's so much that we can do mechanically with precision agriculture. There's so much that we can do with computers and precision agriculture. But if it doesn't make agronomic sense, there's no point doing it. So I just want to hone that back in again. Um, there's there's no point in variable rating if it doesn't make sense agronomically. That's the whole thing that we're trying to do. So, okay. Just had to get that in.

Kyle Okke:

Um, that's a great point. I've actually had uh so so my one of my well, both of the the farms I work with in Montana, they've they both have big fields, but I've had them asked before uh to this exact point you made. They'll look at a map like this one doesn't variable rate at all. Why why is that? And I'm like, do you want me to variable rate it by 10 pounds so you have a pretty map?

Sarah:

Yeah.

Kyle Okke:

Or or you just go, you have really high phosphate in this field. So all we need to do is run a basic starter.

Sarah:

Yes.

Kyle Okke:

Across everything. And and so it's in starter fertility. Uh and and as soon as I explain that, they're like, oh, oh, okay, well, it's good to know. I just want to know. It just it didn't, it didn't, it it was in the it was in the prescription as no rate change. I'm like, nope, that was on purpose. Like we don't need to make it variable rate if it doesn't need a variable rate, but you'd make it a map still because the standard practice is you're used to uploading that stuff for fields.

Jodi:

So sometimes the variable rate answer is a flat rate.

Kyle Okke:

Yes. So so yeah. So great point.

Sarah:

But not when it comes to residual herbicides with a lot of changes and a role. See how I brought that all back?

Kyle Okke:

Yeah, yeah. So yeah.

Sarah:

So pulse with modulation.

Kyle Okke:

Yes.

Sarah:

Super fun words to say. Talk to us about that.

Kyle Okke:

So this was probably uh case IH through the AIM command uh trade name is probably where this has been the most popular. But although every piece of equipment has it, I think actually the original uh pulse with modulation system that existed was from Capstan. And they called that a sharpshooter. And and then I believe Case IH just has licensed that from Capstan, or at least their original rendition of that. And now, and now just about every brand of sprayer has their own like brand-specific version of it. Like John Deere, the other big one in the game, has has exact apply. Um I was gonna say Precision Planting has their own system now, Capstan continues to do their system, and there are others that exist out there. But what that is doing is is decoupling the change in pressure to the rate that's being pushed through the pump. So pulse width modulation is decoupling the pressure change. So the pressure change remains static, but what is actually happening in pulse width modulation, and I'm sure that I know this is this isn't something specific to agriculture. This is definitely like an engineering thing, and and I think this gets used a lot in like pulse width modulation, if I'm not mistaken, is more about like electricity delivery than it is about anything else. But what it means to us and agriculture is that there is an electrical solenoid on every nozzle body, and it is controlling a plunger that's acting like a gate valve for water flow. And so this pulse width modulation is like intermittent electricity that's that's coming into the solenoid and it's activating and deactivating a plunger. So it is stopping and starting the flow of water coming through the nozzle body, and and how it adjusts the applied volume as you speed up or slow down on traditional spraying is that you're you're setting a uh a duty cycle, they'll call it, of how many times that electric pulse turns on and off and turns that plunger on and off on all of those solenoids uh a second. And so it'll be uh in hertz. Uh it'll say like how many hertz are you gonna run? And and but they'll say you need to run from somewhere between like 50 and 70 percent uh duty cycles, saying that like let's say if the nozzle turned on 10 times a second at 50% duty cycle, it's it's plunging in and out five times for for easy figuring, but it happens a lot faster than that. So it's like a lot of times a second. It's not just 10 times a second, it's like 50 times a second or something like that. Um it it's crazy fast.

Jodi:

It's it's so cool. And like let I want to paint a picture quick because I this whole concept of like what is pulsive modulation, what does it look like? That really made sense in my head, right? Because Kyle described it in a really, really great way, right? There's these plungers that turn on and off, allowing that water to flow through. But what does it actually look like in person? I mean, if you think about a sprayer like turning a row, right? And you've got the inside of that sprayer, like if it's turning right, you've got that right hand side of the sprayer that's kind of just staying in place while the outside side of that sprayer is moving really fast as it whips around that corner, right? And so with like pulse with modulation, the inside nozzles that aren't moving very quickly, like where you're turning, they're gonna turn on and off less quickly than the ones on the outside. So that even though you've got different speeds at different sides of the boom, you're still applying the same amount of water volume over the acreages that you're covering. So, like if you're going slower, you're gonna have slower pulses. Like you're gonna, you can see like the droplets coming out of the sprayer. And then like as you speed up, you can hear those like solenoids going on and off, and you can hear it go faster. Like, is that painted picture? It it's you can see it in action when you speed up and slow down.

Kyle Okke:

Anyone that uses that sprayer and is applied with it or watched it go, you you see exactly what it is because you can you can hear the spray turning on and off. Yeah. Um, you you see it. What you just explained, Jody, is turn compensation. Yeah, much like using using using pulse width modulation. And there are pulse width modulation systems that only work by the boom section. So they don't necessarily have nozzle by nozzle control. And so you have to the that's on unfortunately to the farmer, that is technology you have to pay more for to have, but it it it does, it's there and and all that. So depending on, but but the overall, let's just pretend the whole boom is using pulse width modulation still. When when you speed up and you're applying your static rate, you need to increase your pressure on a standard system. Well, now it's just it's it's already pressurized, and all that's changing is the duty cycle increases. So it's just turning on and off more times a second to get that extra water volume applied so that it's still applying the target rate. When you slow down, and this is where anyone that uses a sprayer with the system really sees it, you get into that classic field border situation where you lower your booms and you slow down because you don't want to drift, it's automatically compensating when you slow down to a crawl. All of a sudden, you see those you can see how many times it's turning on and off because it it's like, whoa, okay, we got to go down to like 10% duty cycle to get our water volume right, and then you just see these poof, poof, poof, poof, you know, like it's going in slow motion on the on and off of the nozzles. And and then that's generally also where you see uh poor control like your field borders and some because you're not getting the coverage you you need to get out in that situation. So those those nozzle bodies are all they're designed to be run at least, you know, at like that 40 to 70 percent duty cycle. I mean they have to.

Sarah:

But at the same time, your spray pattern is always going to be consistent. Yes, because you've got that consistent pressure of going through the nozzle every time.

Kyle Okke:

Yes, the pattern on the nozzle is consistent because it's always running at the pressure you set it for. So it's never lowering, it's never going higher, so you don't get the driftable finds, you don't get the collapse pattern. So so that's so that's that's the concept behind that. And so when it comes to variable rating, then the herbicide, where now we're talking from five to ten gallons, we don't have this crazy like slow down, speed up kind of thing that happens when we're lowering the applied volume or raising the applied volume. The duty cycle is compensating there, so you can still just maintain for the most part your average speed, and the duty cycle is what's changing when it's variable rating to compensate for that.

Jodi:

Beautiful.

Kyle Okke:

So that's so that's how it's accomplishing that. And then you don't change spray quality, pattern quality, and you're still achieving as good of a post-emergent spray pattern as you possibly can get. And and then less strain on equipment and all that of it, the speeding up and slowing down and all that kind of stuff.

Jodi:

So in this case that you're talking about with pulse with modulation, you are changing the rate of your tank mix, whatever you've got in there, whether it be the residual herbicide or a that and a partner, you're changing the rate of that application based on gallons per acre applied.

Kyle Okke:

Correct. Yep.

Jodi:

And then you can keep a consistent pattern with the pulse with modulation.

Kyle Okke:

Yep.

Jodi:

So Do you have any or go ahead?

Kyle Okke:

Or no, you you ask, and then we'll go.

Jodi:

Do you have any sprayers where you have direct injection where you can change the rate of what that herbicide is?

Kyle Okke:

Unfortunately, I do not. Because that uh I'm glad that you brought that up because that was kind of the direction I was gonna go. There is uh direct injection where that is tied to a rate controller, and you could have uh, you know, where the sprayer is constantly doing the target rate. So let's just say it's 10 gallons per acre or 15 gallons per acre, whatever the standard target rate is. It will keep that standard target rate, and then it's going to direct inject at variable rates into the spray boom. Now, I don't have the the fortune of working with anyone that has those systems. That type of system should work. I've certainly thought about that too. Um, I'm sure there's kind of growing pains with learning what to do there because I'm sure there's like a look-ahead time that you really have to be focused on on that because it it does take time if a direct injection system is hitting like your main hose coming into the boom, and you have a hundred feet, 120 feet, or hell, some of these sprayers are out like 160 feet now. So it takes it takes time to get that rate all the way up to the end of the booms, and so that's I I wonder how well variable rate would work on a direct inject system because of the amount of a lot of sprayers are going 15 plus miles an hour. Is it going to compensate it it takes it's gonna take seconds to well, probably more than seconds, maybe like a dozen seconds or something like that to get spray from the center of the boom all the way to the out to the edges, and so barrel barating something you might end up with like these weird like of the pattern triangle patterns coming in and out, and so that might not be the the answer, and and you don't see those systems necessarily used too streamlined, anyways, but I'll bring up another system, and and John Deere's the one that's paving the way there, but they are not the only one that's out there. There are other sprayer manufacturers that have dual tank systems that could have dual plumbing, could have dual wet booms, all that. But oh, so now you're talking about actual dual dual tanks and dual um so so let's let's talk like a John Deere C and spray ultimate, not not none necessarily the C and spray part of it, but that's what they call it. Okay, so when you buy a sprayer with the C and Spray Ultimate kit installed in it, that has two tanks, it has two tank fills, it has two live booms on it, and so on that whole boom, there's two wet kits, two sets of nozzles, everything on that sprayer. And so I think those tanks are set up in like a 60-40 configuration. So let's just do for easy figuring. If you're running a thousand-gallon tank, which I think they're a lot bigger than that, but you're you're running a 600-gallon tank and a 400-gallon tank, and then they have dedicated plumbing to go out to individual nozzle bodies. Now you have the ability to keep something like sulfentrazone in a tank by itself, and that can variable rate your water volume as as you're going through the field, and you don't have to worry about the tank mix partner because a tank mix partner can be in their very own tank and be independently run.

Sarah:

And you could maintain that con if it's a post-emerged herbicide, for example, you could keep that constant um water volume in there. That that sounds like a system that could actually work out pretty darn good. That's pretty fun.

Kyle Okke:

Yep. And so I think uh I think that's something that could work out really, really well. And and then you could take that a step further too. And if if you're going after the green on brown, you know, kind of thing, you could have you could have that, you know, running at a static rate, at a static pressure with a tank mix that you're doing an on and off green on brown sea and spray, and then you're just on the whole background side on that second tank, be running a variable rate residual. So, so that's like the ultimate tech that that comes there. And and so uh, you know, I think John Deere on the equipment side is so focused on just the the sea and spray part and like a static residual. And they're and I think they've been focused heavily on like the in-crop part of it, but I think what you'll see come into play, especially is like I mean, these systems are expensive, right? And so it and so interestingly enough, um, we have more of those types of systems in North Dakota now, but actually the place that adopted a a heavy use of those is Western Kansas.

Sarah:

Really? Yep, and you're talking about the C and spray technology, just C and spray in general. Okay, yeah.

Kyle Okke:

Um, I don't know necessarily the the ultimate, okay, but no matter what, like you're you're talking a pretty substantial upgrade. Like the cost of that system, you could buy a used sprayer in all that.

Sarah:

Right. Absolutely.

Kyle Okke:

That that you know, you couldn't buy a brand new sprayer, but you could buy a pretty decent use, high, high, high clearance self-propelled sprayer for the cost of these upgrades, but as but it's all an economy of scale, and so why I say like you know, like it was uh oh uh I'm trying to think of who was talking about this.

Jodi:

Uh Josh Sherman.

Kyle Okke:

No, we yes, we've uh we've all talked to Josh. I know you guys have. I've listened to your podcast with Josh on on these things, but um uh Sarah Lancaster from Kansas State.

Sarah:

Oh sure.

Kyle Okke:

Um Ed actually Ed actually showed up to uh our Wild World of Weeds seminar, talked about this and shared about those systems. And basically, as you travel west in any state, you have uh the farms get bigger, the scales bigger, and then like we talked in the previous section of this podcast, that the bigger the fields are, the more variability you do inherently end up seeing, and where variable rate ends up making more sense. Well, just the bigger the farm, having those it it just makes financially more sense if you have more acres around across on that piece of machinery, and all of a sudden you see the savings, you know, to running that type of a system, you know, where a where a traditional smaller farm or or maybe just more of your traditional farm size can't stomach you know that that kind of a cost initially. So so I think I I think those systems will probably come online more with some of these bigger farms further west, and we'll see more use of like these dual tank systems and what was the big cost-saving driver for the Kansas farmers?

Jodi:

I mean, I remember a couple years ago when John Deere and I think there was another company that introduced like the picture-taking capability on um booms in order to do like the the green on brown. And I think farmers in Montana at that time were saving, you know, thousands of dollars on their acres covering summer follow, um, just doing the green on brown. And I quite say cost at that time was really expensive too. So really did a great job of saving. What is the driver down there that helps them get that saving for I I think there's plenty of like fallow situation that they have there?

Kyle Okke:

Or well, you think, okay, so lot like Kansas right now, a lot of their harvest is happening right now. Well, they're they're not necessarily double cropping soybeans into those acres, especially western Kansas. It likely sits idle now the rest of the year until they plant corn the next spring. And so that's very similar as you get north to like a Montana area, and they do a lot of summer fellow. Or you get, you know, parts of Western Canada and they do summerfellow. Um, the cost savings are probably more from not having to make repeat trips. So those dual tank systems, you have the ability to run a green on brown spray. So you're only spraying glyphosate where it needs to, but you don't have to make a second pass on those acres as you're laying down residuals to try to reduce the amount of passes you make. Because that's that's a big chem fallow play, is let's just not keep spraying glyphosate over and over and over again. That's a great way to make it not work, which unfortunately they've discovered that that yeah, it it's already like that. And and same thing if you're adding like dicamba and all those, like the the original dicamba resistance in kosher actually comes out of Montana, out of farms in like that that uh uh you know, just like north of Great Falls, Fort Benton, Haver, that area. Um, it it wasn't from people applying it to Dicamba toller and soybeans here. Although they're finding out that too, you know, that camba is building resistance a lot. Probably already had some selection pressure exposed to it. But I think that's I think that's the driver for the these western uh if I'm gonna speculate, these western Kansas farms, because that's how I would see it with anyone I work with, is if we had a lot of chem fallow or post winter weed, where we want to keep that weed free, you know, for the remainder of the season, which they're they generally don't see that much snow in the winter because of how much further south they are, and so you're you're just trying to keep any kind of weeds from growing and pulling through. So you you have to rely, and you don't want to do actual tillage in a lot of cases if you don't have to. And so it's chem fallow. And so you're applying a residual to keep the amount of passes you make. So if you're able to do green on brown spraying and laying a residual at the same time, and that reduces the amount of times the sprayer has to be in the field, that's a big win. That's a pretty that's that's my speculation why it's more popular.

Jodi:

Yeah, no, that's that makes a lot of sense. And I think what I'm hearing you say is that folks that are looking at doing getting into these bigger systems, the CN spray systems, etc., and if they do have the two wet boom kits, don't sleep on the variable rate capability for the residuals, because not only would you be able to potentially cost save for chem thallow rate like overall herbicide reduction, but and pass reduction, but you could be reducing the amount of carryover for and crop response from herbicide applications if you variable rate that too, the residual side.

Kyle Okke:

Yep. So here's here's some bonus stuff for you guys. In in so I'm coming out of left field here, but you're gonna like this, and it's not gonna surprise you. Um so this still falls under precision application of residual ingredients, but I I think there's one one another use or another future in in this that's not just a row crop situation, okay? So the C and spray systems are focused on corn soybean row crops. Eventually they're gonna get into like real-time detection on wheat, I think, and some of these other crops. But I think there's a good like utility use of drones when you uh run into certain situations, okay? So here's here's kind of two situations that come to mind for me. Okay, first one where uh even though kosher is a tumbleweed, everyone that deals with kosher as a problem could probably all agree with me on this general sentiment, is that it seems like it comes up in the same places over and over and over. Like there's always perpetual problem areas, even though in the winter time that's mechanism of dispersal is tumbling across the countryside and dispersing its seed. That's how it spreads new stuff. But where it is a perpetual problem, it always is a problem.

Sarah:

Yeah, like in the salty areas. I you know, I see it in a couple of salty areas and it concentrates in there in a couple fields.

Jodi:

So okay, you have it in a video game, it always spawns in the same place.

Kyle Okke:

Yes, and and it's not and and and sometimes those salty areas aren't visibly evident, you know. Like I've had these very good discussions with uh the farms I work with too, and I go, these show up in the same spots every year, and they're like, oh no, I don't think that zone's as bad as it is. And I'm like, no, no, it is. It just just because it's not white doesn't mean that it doesn't produce a poor crop. And and there's a really good example of that. So we actually put a uh a corn hybrid trial, just a small strip trial. We just we just took the the three hybrids he was growing on his farm, and then I added uh two other hybrids from another farm and that that they had that he was interested in, and we did it in a strip trial. Well, as we're putting stakes in the ground, we were at the headlands of this field, we're in a poor area based on the zone map. Well, I had the damnedest time punching stakes into the ground. The ground is so hard, visibly doesn't look that bad. Those are the same areas that we have a lot of the perpetual kosher issues. Guess what? You have higher elevated soluble salts. The ground is like very just like the soil structure is degraded where you don't get good water infiltration, so you get this buildup of salts. It isn't physically white, but the crop never canopies very good, the roots never grow good, the the crop never yields that great, and so it leads these perpetual kosher spots year over year for-wheeling these fields. I see them in the same over and over and over again. So uh now I own a little DGI Mavic 3 Enterprise with a multi-spectral camera. One of my goals with that is to fly over these fields when there's no crop and those weeds are coming there. I want to map these populations with the goal of having an or of potentially just even a variable rate fall residual map. So and so fall residual, we haven't been variable rating. Fall residual, we've just been putting out a static rate across everything. And there on fall residual, everything else is dead. So all we're doing is water residual, variable rate, the the water volume, no real like implications to that. But if we know where we have the issue areas, and we also know the other parameters involved, and then plus it's fall, like we got a long time for things to kind of you know cool off and and not cause as much crop injury. I want to hammer on those areas even harder with with higher.

Jodi:

Yes, spawn sites.

Kyle Okke:

Yes, try, yes, trying to get rid of the respawn sites because those are the point sources of the damn weeds.

Sarah:

I love it.

Kyle Okke:

Yeah. So so that's that's that's one use. Another one that I wish I would have had this year is think about every time in a wheat crop when wild oats come out.

Sarah:

Yes.

Kyle Okke:

It's the grass that falls in between the rows of the rest of the grass that's growing in the field. That with good high resolution imagery would be extremely easy to detect. And wild oats, their mechanism of dispersal, they're not necessarily going into the combine, getting ground up and spit back out. They're dropping before harvest. And so wild oats typically don't end up being super duper widespread across the field unless it ends up getting really, really bad over time. But if you get it on earlier detection, you can you can get these wild oats patches where they don't grow and they just keep staying in the same spots. And so now we take like your products like Zidua that have really, really awesome or Fargo, yeah. Yeah. If if tillage enters the chat and you can do incorporation, um, but but you take okay, so there's multiple residual products for wild oats, and and for us in you know, 50 bushel wheat country, um a $20 application across the board of a wild oats residual is is a tough pill to swallow at the price of wheat right now.

Sarah:

Yeah.

Kyle Okke:

But if you could identify where those wild oat patches are at and predict where they're going to come up because they are predictable where they'll come up. And now you can apply that to only 20% of the field where it needs to be, and you could do it at a higher rate. Not only can you put it at a higher rate to prevent that patch from you know getting out of control, but you can also do it at a higher rate to really prevent that from happening and do it uh economically across the acres. So you're still applying less than you would have to begin with. So maybe you can take that $20 application and make it a $10 application.

Sarah:

So this has been a fabulous conversation with Kyle about a lot of the actual equipment concepts that go into um making variable rate uh herbicide applications actually work both from an agronomic and an equipment standpoint in the field. And and so we've talked of this this podcast has actually gone quite a bit longer than what we thought it was going to. You know, we started talking about in the previous episode about general concepts of the whole residual uh variable rate residual herbicide concept, and this time it was all about the equipment, and we haven't even talked about mapping yet. So we're sitting here and I think we're going to have Kyle back again because we're already about the end of this uh end of our time here, and we'll we'll come back and and chat again about actually mapping this stuff because hey, that's what we actually do here at GK Technology. Um because at GK Technology, we have a map and an app for that. See ya next time.