Ag Geek Speak

17. Variable Rating Herbicides with Kyle Okke Pt. 3

• A Podcast for Precision Agriculture Geeks • Season 2 • Episode 17

Share episode

We map residual herbicide rates with field truth, not guesses, turning five-zone soil maps into targeted prescriptions that cut injury and hit weed spawn sites. We weigh OM, pH, texture, and landscape to protect sensitive crops now and keep rotations flexible next year.

In this episode we discuss...

• base maps from precision soil sampling and scouting knowledge
• modded zones for unique poor areas and weed hotspots
• organic matter, carbonate, and color as soil clues, not absolutes
• extreme pH swings shaping efficacy, injury, and carryover
• decision framework from damage mitigation to suppression
• variable rates to protect sensitive crops and rotations
• SmartFirmer OM layers and controller-friendly rate steps
• lidar, soil series, and as‑applied maps to refine zones
• practical limits of sensors and when algorithms help
• closing insights and where we push rates or back off

Missed the first two parts of this episode? Check out our previous episodes! https://www.buzzsprout.com/2297340


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 written product for my friend. And I can't wait to get in the fields again. No, I can't wait to get in the fields again.

Sarah:

Welcome back to Ag Geek Speak. We were having so much fun talking with Kyle Okke for the previous two episodes that we thought we'd bring him back for a third. Third times a charm. Truth be known, we were having such a great uh conversation about variable rate pesticides in particular, herbicides, that we thought we would um continue the conversation. In the previous two episodes, episode one of this series, we talked about the concept of, you know, just what this variable rate residual herbicide concept is. The second episode, we talk a lot about the equipment and the actual sprayer technology that's needed in order to make this happen. But we've concluded the second conversation. And here we make maps at GK Technology, and we haven't even talked about mapping. So let's get back into it again, Kyle. And um, first of all, help us understand just roughly like when you start to think about even putting together a map, where do you even where do you even start with trying to figure out the data that you need to figure out how to variable rate this this?

Kyle Okke:

So I guess where I absolutely started on the on the the coarsest level without getting into the fine details, is I I am still just utilizing the zone productivity maps that I soil sample off of.

Sarah:

Okay.

Kyle Okke:

So I I I am in a lot of cases using that very map still. And and especially when everything kind of lines up nice, like I was saying offline. I said the my favorite part about using ADMS is that the user has full control over what you're doing. And so there's nothing, uh not yet, anyways, that a fully automated zone making system that is gonna get it right. It takes intimate knowledge of the person doing the mapping of the field to really uh and that takes collaboration with the person that farms in some cases, or and in many cases, I should say, uh, and then or or you're the agronomist that's out four-wheeling in that field all summer, and you see how crops produce on there, and you go, well, that bad spot is bad because of this reason, and that bad spot over there is bad because of this reason. We we focus a lot on the poor areas, which happen to be the driving force behind making these variable rate residual maps.

Sarah:

Okay.

Kyle Okke:

And so, yeah, so it so you see a poor area because maybe it has a thin clay pan six inches under the ground and it accumulates a lot of soluble salts. And no matter what, that area probably isn't gonna grow field peas very well. It probably isn't gonna grow sunflowers or some of these other things really well. I personally want to put more product down in those areas because that's the respawn spot for for uh kosher as is the big driver there. And so I'm okay with it being a sacrificial to the crop area if I can try to hammer it harder with a residual herbicide in that area.

Sarah:

And reduce the overall seed bank uh for the entire field is kind of your thought process. The weed seed bank. Sorry. Okay.

Kyle Okke:

I I actually have other ideas around those areas, but I'm not gonna go there yet. Um, but but then, anyways, you know, so you have you have pore because of like the traditional where we're reducing the rate because it's coarse soils and high organic or uh coarse soils, low organic matter, high pH. Um, those areas and and those are uncovered. Yeah, once you make a really awesome zone map, because you're using ADMS, you're using your personal knowledge of the field, you're parsing out and you're doing the mod zone thing. So you're you're you're all of a sudden going from your standard, you know, five zone map or three zone map, let's call it, but I like five zones, and now you're modding things and you're going, well, this poor area is because of this reason, this poor area is because of this reason. Totally different landscape position. So all of a sudden you have your five-zone map and it turns into a six or seven or eight zone map.

Sarah:

Yep.

Kyle Okke:

Because of because of those things. And once you have those parameters separated out, and now you're and now if those extra zones are big enough, sometimes they're small. You're like, oh yeah, well, that's that's white. The ground is and all it does is grow kosher. You're like, I don't really need to know much more about that. I don't need to soil sample it to tell you that it's got a thousand parts per million sodium, and the pH is like nine, you know, things like that. But then you have, but then you'll get these bigger areas, and you're like, well, no, crop grows in them. And so then then you start, but once you have them separated, all of a sudden the results make a lot more sense when you get them. And then and then that's the power of that. So that's the base map, I guess, that I've always used for doing the variable rate residual applications because you know, went through the due diligence through your guys' help initially teaching me, you know, what what to you know how to mod those things out, and and and then all of a sudden the results make sense. And then so that's that's really the majority of the map I use is my base map from soil sampling.

Sarah:

But one of the things that I have enjoyed about when you're soil sampling in the fall of the year on your social media accounts where people can follow you, I I love it when you go out and you soil sample these different zones and you are showing just even the different colors of the soil in the buckets, yeah. Huge differences. And then when you put that with the soil sample results beside that, uh it's just amazing. So, can you in some of these fields that you manage, can you help us understand the diversity of soil parameters that would affect the activity of a residual herbicide? Like what's the variability that you're that you're finding across some of these fields that you're managing?

Kyle Okke:

So the color really stands out. The color of the color is the tail. You you can you can go from like this nice, really dark looking soil to like almost a very light tan or white in some cases, and and the color difference is actually mostly organic matter. That's that's the big difference there. And so you can generally tell high versus low organic matter, although the soil, the soil test tells you exactly how much organic matter. It's way better at telling you the true organic matter in those areas because I've had these huge color differences. I'm like, wow, this must be like a three or four point organic matter difference because I do have that big of a spread sometimes in fields. But I've had those huge color differences and still only be like a point and a half of organic matter change.

Jodi:

That's a really good observation, right? Because like one thing too, you mentioned about your high spots in your fields, like your hilltops, those tend to have a higher calcium carbonate level or higher pH, which means there's likely a lot more calcium carbonate.

Kyle Okke:

It's totally what it is, yeah.

Jodi:

It it's it's white, like it imparts a whiteness to the soil. You can see that here in the valley, um, places with high calcium carbonate. You can see that whiteness in the soil. So yeah, like you were saying, organic matter is uh contributing to the color, but there's other things too that can be a part of that that are contributing to it.

Kyle Okke:

Definitely other parameters that are affecting that. But but yeah, it's like seems like organic matter is the big one, right? But yeah, the calcium carbonate. So so there's things like I don't know, gives you your agronomous spidey sense on that one. You're yeah, you're looking at that, you're like, oh, okay, yep. You can really see the difference here, and and yeah, then when you see that like really light color, you're like, hmm, that must have more calcium carbonate in there. Because there's some that are just plain red, you know, and you get that too, and that's maybe more like parent material than it is anything.

Sarah:

So, and that's interesting because in your neck of the woods, not only do you apparently have these areas where you've got accumulations of calcium carbonate, which for the world out there that wants the layman's term, that's lime. Okay. So if you have a low soil pH, what do you do? You apply lime. So that's just areas of accumulated lime, high pH, but then you also deal with a lot of low pH areas out there. So it's interesting to me to think about this uh residual herbicide concept from um even a soil pH parameter. So what um what what are some of the soil pH differences that you can find out there across uh some of some of some of your fields?

Kyle Okke:

Well, if you like here here's the highest and here's the lowest that I've seen. So the highest I've seen into the high eights, um, like 8.7, I think, is maybe some of the highest I've seen.

Jodi:

Oofta.

Kyle Okke:

Yeah, oofta meta. Yeah, pretty high.

Jodi:

Yeah.

Kyle Okke:

On the low end. Uh I've I've been in the fours on on the low end. Now that's extreme. Like the only time I ever ended up with fours in soil sampling is diagnostic soil sampling. And so that's those are the places I've done that where I had the combination of something's not right in this field, and the these patches are like dead. They came up, but they're dead. And it's like, what's going on here? This year we did some again at uh Durham, which is susceptible to acidic pH. Or it's more, I would, it's not as susceptible to acidic pH, it's susceptible to aluminum toxicity more so or more sensitive than hard red spring wheat to absolutely low pH problems then. Yeah, to to the problems associated with low pH. There we go. And and diagnostically soil sampling, very specifically, like the spot on the spot. Yeah, we've got some four down to like the low fours. Oh and I've heard of some in the high threes. I've heard in those areas. Yeah.

Jodi:

And those diagnostic tests, was that zero to three or zero to six that you were getting those low fours?

Kyle Okke:

I I haven't uh I haven't diagnostid zero done zero to threes. It's all been zero to six.

Jodi:

So even at a zero to six, you're getting to low fours.

Kyle Okke:

Yeah, I guess that's the barometer I put myself on stuff when I'm like, hey, I'm in the low fours on a zero to six. I I could give two craps about the zero to three because most of the time you'll get, I mean, you'll see where it's lower pH in there because that's stratified. But when you're now taking your entire acre furrow slice and you're seeing that low, you're like, we got a problem.

Jodi:

Yep.

Kyle Okke:

Tillage can't fix that problem.

Jodi:

No.

Kyle Okke:

Flipping flipping the soil over isn't gonna do it. You know, this this is uh that that's called your base material doesn't even have enough calcium carbonate in it to to overcome this. You gotta add it. You know, so that's that's definitely so so diagnostically sampling, but I I would say like on a normal, like when you look at the traditional precision soil sampling that I've been doing, I do see in the low fives quite often.

Jodi:

Which is indicative that there are spots that are below five throughout those areas that absolutely and and thinking about Sarah's question and and about like how you're putting these maps together and how you're choosing rates, like I'm guessing it's probably a field-by-field basis of like Yeah, you're in a field. What do you look at first? Like, do you say, I know I need to reduce the rate for the hilltops to focus on crop safety? Or I suppose you what's your thought process? Where do you even start to make the decision on how you're gonna vary things?

Kyle Okke:

So the only farms that I've been doing this with on the variable rate is one, they have to have the sensitive crop that we've have the history of going what we've been doing at flat rates is detrimental to the sensitive areas. So it starts there and then it also kind of goes like do we have a manageable weed population? Because if we're gonna reduce the rate, are we gonna be okay doing that? You know, like even if you have perfectly clean, clean fields, it doesn't mean that you don't want to use uh residual herbicide at all, right? Especially in these specialty crops, because we do not have a post-emergent option that's very effective. The best option is the pre-emergent option. So even with clean fields, we still want to apply something to the field so we have a layer of protection. So we're we're gonna be putting something no matter what. But I've got some farms that I'm like our kosher pressure is far too great. Um, sometimes I've just like said, no, you're not planting sunflowers, not in this field. We're you know, so I I've I've I've legitimately had those conversations. And we and we joke about that. I go, you know, and I I like one of the guys was the first year I worked with them, and and I said, I'm not gonna rock the boat, I'm more here to like help you along, make sure there's no disasters, but I don't wanna I'm not gonna change a lot of what you do. I want to know how you operate first. And I remember seeing one of the first fields and it was slated to go to to Sunflowers, and I'm like, nope, this isn't happening.

Jodi:

Nope.

Kyle Okke:

I was like, not happening. Yeah.

Jodi:

So so it sounds like uh in general, right? Like you're going in with the purpose of okay, are we are we trying to reduce crop sensitivity here? Like that's that's probably the main goal.

Kyle Okke:

And then that's the that's the big driver, and then as time's gone, and and so this takes field history. So this this is you know for the field, the farms I consult for. And it's like I was saying at the you know, in the previous uh session is that we have these perpetual problem areas, and and that's where now we're looking harder, going, okay, we can identify these perpetual problem areas, know that with the rest of the parameters we have in those areas, we could run a stronger rate without without injuring our crop because we have the correct parameters. Now, now we're looking at, you know, how do we layer on top of this or how do we, you know, adjust what we're doing instead of just just being a damage mitigation to the crop, but actually being effective or more effective on our weed control basis by running stronger rates of residual where needed.

Jodi:

I also like you've oh go ahead, Sarah.

Sarah:

I I also want to throw in that this can help us manage our rotation for next year too. There's so often where where we're we're dealing with especially with specialty crops where there's not a lot of herbicide options, you know, we want to make sure that we are managing the weeds in the crop the year of because we know we're gonna be raising more of these specialty crops going forward. And that rotational restriction um going to future crops can sometimes be a challenge. So, you know, let's say you've got a soybean acre out there with self-entrazone and you want to go to, you know, some other crop out there where there's rotational restrictions. Hope, you know, even if you're applying an average rate across a field that is by the label, if you've got these variable areas within a field, that rotation can really get affected in spots. You can see the effect the the next year. So you know, yeah, we have to make sure that we're maximizing the weed control in these areas. We need to make sure that we're minimizing the injury in the year of, and we also need to make sure we've got that rotational restriction that's actually gonna work um the following year, too.

Jodi:

And it sounds like Kyle, like right now you kind of have like a basic level, like level one, let's just mitigate damage. But then, like beyond that, like you said, like wouldn't you have a feel for the crop history and how things respond? Like level two is like, okay, destroy spawn sites. Can we increase the rates a little bit and make make the herbicide more effective? And then level three might be okay. We can even push some rates further in areas that have different pH levels that we we can see, or uh what are some other things? Are there anything else that you consider to like increasing your rate?

Kyle Okke:

Um, so so base level, like level one kind of style is is using that very well thought out zone map that has the mod areas so that you have correctly parsed out, you know, zones that that are representative of the actual parameters that are making them the poor areas. Okay, so so then so then you have as accurate as possible, which that's like the big leap into it. But then there's there there's actually pretty decent equipment out there, and so one of them is I have the fortune to work with two farms right now, and they have these smart firmers from Precision Planting on their planters, and that has an organic matter screen on it, and so it makes this really nice organic matter map, and so it's not it's it's relative organic matter, but it it it's pretty close. So it so if you take the organic matter map, which it makes this really awesome granular organic matter map with a with a real fine detail of where it's high and low, and it gives you kind of a general percentage organic matter, but it's relative, you know, it's not calibrated, it's just a relative organic matter. So if you take your knowledge of okay, soil sample says this on each zone, and now I have my organic matter map from my smart firm or planter, it's super cool data. You you go you immediately see like where the lowest stuff is, you're like, that's exactly where the injury is happening the worst.

Sarah:

Are you kind of like cross-calibrating it then back to your your soil sample results that you actually get from from soil sampling, and then you can see the variability from the smart firm or map?

Kyle Okke:

So so I haven't been cross-calibrating necessarily because I I think still in the end, like unless you have nozzle by nozzle control on uh your sprayer, you can't get super granular with your application. You're still applying across your whole boom for the most part, and so you still gotta remember, like where we have this like super fine resolution kind of data with like yeah, you know, so so we can paint this data with like these really fine brush strokes, but we're like using a roller painter for your wall for the application.

Jodi:

You know, we're going to the Bob Ross episode. We talked about that back in season one of Ag Geek Speed.

Sarah:

Happy Trees, happy trees.

Kyle Okke:

Yeah, yeah. We have we have the Bob Ross of of map quality, but your sprayer is more like your commercial painter for a house. You know, like like sure, you can you you can do so much, but you can't, but that commercial painter isn't gonna be able to do what Bob Ross does. So you have to keep that in mind. So so that's back to like where those layers of information are extremely helpful. And for me, it's helping make the decision, like there might be certain like areas that I mod that I go, I do actually want to shut off self-entrazone on a couple of those because it's it's so low in organic matter, like it's it's finding the bullseye. And so then then you can cross-reference and go, hey, yep, this area is definitely big enough. This this'll actually make a few cells for the rate controller to actually catch where it could shut it off.

Sarah:

So when you have so you primarily use zones, your productivity zones, and you assign your your carrier rate to the zone, and so your variable rating, your carrier rate, and you know what your active ingredient rates are gonna be going into that carrier rate. Um once you have that prescription built, have you ever modded or changed areas within the prescription itself to do something maybe a little bit different or enhance, you know, the the prescription that's coming out of the those um those zone assigned rates?

Kyle Okke:

Yeah, yeah, there's definitely modding the whole way through. Like I said, it it like it's kind of that's the fun part about ADMS is that you can get as very detail specific as you want and all that. You know, so uh the the big one is instead of having like these nice i uh feathered rates, you you kind of um I've been going by like single gallon breaks. So so then the zones go by the the changes are single gallons at a time. And depending on the the rate controller, it seems like uh like the the John Deere and the Raven stuff, I've just gone single gallon rates that's handled it flawlessly, no issues. Um like a Pro 700 seems like and the Trimble systems seem like they're just any any way you can make it more simple, the better it performs, and then then instead of doing like you know, I cut it in half even more, so then it's gone to just like like if we're gonna go from five to ten gallons, I do a five, a seven and a half, and a ten instead of like a five, six, seven, eight, nine, ten kind of thing. And and do the rate changes like that. So the rate controllers I've played with a little bit by you know changing my my parameters within each zone. Uh that way. I also like to do the mod area thing and and I and and I'm c so this is like where you know like all of us that spent a lot of time on ADMS have multiple screens. Yep. And so so I'll have a screen of the lidar overlay with the zone map, and and I'll have that screenshotted and on one screen. I love I love using the University of California Davis Google Earth extension, and I have that on one screen, and so I'm looking at like soil series, landscape position, and then I'm in here, you know, doing like the the the zone vectorized thing, and I'm looking at those polygons and I'm hitting control or shift or what or shift and click, click, click, click, click, you know, and highlighting stuff and going, yep, these are low landscape positions. I do know that these are you know, like my sacrificial areas or whatever, I'm gonna run higher rates here. And I've gone through and I go mod those up to higher rates because I'm like, I don't want to run that lower rate in those areas, and so yeah, I'm con I'm constantly changing those things, and there's like no algorithm to do that. That's just kind of like the the agronomist's final touch, you know, right?

Sarah:

And it's your knowledge based on how you've like scouted those fields and what you know.

Kyle Okke:

Yeah, and I try to those are hard things to to teach. You just uh that's your intuition, and everyone with their own intimate field knowledge of those fields are the only ones that are gonna be able to do that is you go through, like, oh yeah, that map. I don't like that low rate over there. So I'm gonna just go through here and go highlight these sections, and I'm gonna go re-mod this area, and I'm gonna go smooth this out again, and I'm gonna reproject it. And okay, now this looks good. Like, oh, too many jagged edges on this isn't gonna work for a sprayer. You've got to remember there's like 120 feet at a time. So you keep adjusting, and and you have to see what these as applied maps look like to see how they're capturing it, because that's the that's a big eye-opener to this whole thing.

Sarah:

Good. I you know, so often I think we forget to take a look at that as applied data, and especially as we start moving into these liquid sprayers, that's probably a really important key to reflect upon so we know how to make these prescriptions even better going forward. So, what were what was the eye opener? Like, what surprised you, Kyle?

Jodi:

And maybe you're just about to say that.

Kyle Okke:

Uh well, so uh the this goes this general concept or this general idea goes far beyond just the spraying. But seeing what your as applied maps look like on a sprayer, on a on a drill, on a liquid applicator, whatever, seeing the actual as applied map is really helpful in in helping them, uh, you know, the operator. So if that's the hired person, if that's a custom applicator, if that's the farmer that's running their own equipment, you you start to see like the tails in and out of like zones. Because those tails show up in the as applied maps.

Sarah:

Absolutely.

Kyle Okke:

And and so, you know, you look at those things and you're like, hey, you got to set your look ahead times differently. Or, you know, you you start to look at how those as applied maps go in and out of your zones, and you're like looking at this one poor zone, and you're like, oh, there's only like three swaths that go through this. You're like, okay, that makes me think differently about this. Or, you know, you're like, I thought that zone is bigger than that. It was like only one little tiny grid, you know, one one swath width that hit that. So you're like, okay, I gotta think about this a little differently. And then you can make like small micro adjustments on on well basically, you know, like the cool thing about ADMS is you can get so granular on stuff and you're like, wow, this is such an awesome looking map. But you still have to go back to the it's still the roller painter versus the fine brush strokes, you know, on on some on some of the equipment. You know, and and so then you have you just you and that's okay. That's because you're still achieving what you need to achieve.

Sarah:

And and sometimes you have to think about it differently to get it done with that versus something else.

Kyle Okke:

Yeah, so there's there's so much more little nuance in this that you know, like I've I've never I've never actually sat and explained this to the farmers I work with. We just got like a just really awesome trust level, and they're like, you'll make it work, you know. And and and so they probably don't even realize the amount of like backside that I won't pay attention to the man behind the curtain. Yeah. So it's like I don't I don't try to take extra credit for that kind of stuff. I'm just like it is what it is, you know. It's like my my thing is it drives me nuts to see injured stuff as much as they they see it. So it's like, let's avoid this.

Jodi:

Um yeah, because thinking about it, like data collection-wise, like there there isn't anything that's gonna tell us where these spots are, right? Because Kyle, you're we talked about these levels of what you're varying for. It's both injury prevention and also increasing weed control. Like, what kind of data could you collect from the soil? There's not just one thing or one piece of data that could get you a direct answer as to how to change that rate. There's no sort of sensor. And like, as I think about it, having some knowledge in weed science and soils, like there's not an easy data point that can get you that answer. You need that intimate knowledge and experience to put that map together.

Kyle Okke:

And or it takes a lot of time and money to get the parameters because I was gonna say uh uh but you could have uh through the uh through the company Varus, you have their EC uh sensors, and there's one of them in particular, a couple of them that have uh a pH probe and so it gives you again a relative pH in the field, but that's a very time-consuming process, it's not like a continuous meter. You have to stop, the probe has to go into the ground, it has to sit until the pH stabilizes on the probe, and then when it comes back out, it has to get sprayed and cleaned off. And so it's it's an expensive piece of machinery, and it's very time consuming. And there's a lot of things that can go wrong when you're you're you're be bopping around in a field for well, there's another consultant here, uh, by the name Josh Hammond that owns one of those that that is doing that very thing by getting EC maps and ph maps because he has clients of his that are doing variable variable rate line applications for this. And he's discovered that the pH thing is a very granular, like a very fine change in place to place, but it's the amount of time it takes to make those kind of maps, all of a sudden, is that uh you wouldn't specifically be making that kind of map just for precision applied residual herbicide.

Sarah:

Yes.

Kyle Okke:

It's a nice byproduct if you're going to be doing Lyme applications, you know, because that's going to be the driving force to spending the money to have someone go through that kind of labor with that kind of tool.

Jodi:

But you But think multiple data layers. There's just not just one number that indicates it.

Kyle Okke:

Oh, I was gonna say in a perfect world, you could come up with an algorithm or a or a script and and do this where you have a pH layer, you have an organic matter layer, you have um a soil texture class layer, you would have to have all of those, and and you could run a script based off of those things. But then still you couldn't add your own personal intimate knowledge of the field in there and just go like, you know what? Because of the pH being so high in these areas, it kicked out the high rate. And and the algo says, Nope, you're you're maxed out at this rate in this like poor salt area. But as the ground is goes, I'm sacrificing the crap in that area, and I'm gonna just I'm just gonna punch that thing down to the ground. I don't care if the crap goes with it too. You know, just I'm putting extra herbicide in there.

Sarah:

But with that algorithm, you are going exactly the same direction as I was thinking right there. So that was kind of fun. But uh with that algorithm, rather than actually making the the rate map from that, um, from those data layers, you could actually make another zone map, a zone map that's particular for residual herbicide application. And then you could be assigning your rates for different residual herbicides based on that for different crops. And and you could still have all the opportunity of doing all of the the modding and everything else that you would want to do to your prescription. That's fun right there. I like this.

Kyle Okke:

So there's tons of, yeah. So so this whole topic, there's like we could just keep going and going and going. And so this isn't a simple topic. This has a lot of nuances and there's a lot of application potential.

Sarah:

With that, I really think that Kyle actually just put the nail in the coffin on this conversation, one that could actually go on and on forever. This has been just such a blast visiting with you, Kyle, about this whole concept of residual herbicides from a variable rate standpoint. So thank you so much for your time on all three of these episodes. Again, if you didn't get a chance to catch the first two, I recommend going back and catching uh the first two episodes with Kyle Oki on residual herbicides here. And um thank you so much, Kyle.

Kyle Okke:

Yeah, thank you both for having me on.

Sarah:

Thank you, Kyle, for the insight. With that, at GK Technology, we have a map and an app for that.