Ag Geek Speak

4. Gridding the Zone with Ag Genesis Part 2

• A Podcast for Precision Agriculture Geeks • Season 2 • Episode 4

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Kurt Turner and Lane Bothwell from Ag Genesis share their innovative "gridding the zone" approach that combines traditional zone mapping with targeted grid sampling to address pH variability in eastern South Dakota fields. They've discovered that their most productive field zones often hide significant pH problems that can be economically addressed through this hybrid sampling method.

• Field topography in Eastern South Dakota creates extreme yield variability (corn yields ranging 100-240 bushels per acre)
• Traditional zone sampling works well for most nutrient management in their variable landscape
• Low pH problems tend cluster in high-productivity zones, not poor-performing areas as might be expected (this is not always the case, check your soil test results!)
• Selective grid sampling within problematic zones can reduce sampling points by 60-70% compared to whole-field gridding
• Lime application becomes more economical when precisely targeted to actual problem areas
• Cost savings benefit both the service provider (fewer samples to collect) and the farmer (less lime needed)
• Limited lime sources in the Dakotas make efficient application especially important
• pH improvements are visible within 2-4 years of targeted lime application

If you're interested in learning more about Ag Genesis, check out our previous episode where we dive deeper into their business model and precision ag philosophy.


Sarah:

And now it's time for a Geek Speak with GK Technology's, Sarah and Jodi, friends and I can't wait to get in the fields again.

Sarah:

No, I can't wait to get in the fields again. Welcome back to Ag Geek Speak. We are excited to have our friends Kurt Turner and Lane Bothwell from Ag Genesis down in the Brookings South Dakota area and we had a great conversation last time with them. If you want to learn a little bit more about the Ag Genesis business, I suggest going back and listening to that episode. We talked a lot about how Kurt really does a lot of the mapping in the office and Lane is actually the guy that does a lot of the stuff out in the field doing the ground truthing. It's really an interesting business where you've got that aspect of people really doing the things that they really enjoy the most and it brings out their best characteristics to add to the precision agriculture business that they've got going.

Sarah:

On this episode we are going to talk about gridding the zone. Kurt and Lane are doing something that's kind of unique. I know I've given a lot of presentations on where do grids fit and where do zones fit and it seems like most of the time in normal precision agriculture we're doing either or either grids or zones, but not an aspect where we would do both. So we're going to just dive in and have a little bit of a conversation about that today. First of all, to get things started and just to kind of give a little bit of a conversation about that today. First of all, to get things started and just to kind of give a little bit of reference to where you are and how things are kind of done in your area. I think it's a good question to ask what crops are you raising?

Kurt Turner:

Oh, we're mostly corn and soybeans. There's a little bit of alfalfa very little, but some small grains and then some some forage crops. So but it's, it's 90 percent, 90 to 95 percent corn and soybeans.

Jodi:

Yeah and is uh, is there some silage corn in that too, and like is the alfalfa or dairies yes okay, yep, so you're very I-state. It sounds very I-state or like very Minnesotan of a crop mix.

Kurt Turner:

Yeah, I would say yeah, we have. Our cropping system probably has more in common with Minnesota than it does the rest of South Dakota, but our ground is probably more common to the rest of South Dakota than it is Minnesota more common to the rest of South Dakota than it is Minnesota.

Sarah:

So explain that a little bit. Because obviously when we're working with precision agriculture, we're trying to address the variability of our landscape and how we can raise different crops within that variability. So explain to me when you're talking about how your ground sort of works maybe is more similar to South Dakota, if you were going to describe your ground there, how would you describe it?

Kurt Turner:

Most of our soils are very good soils here but we do have rolling ground and we have some clay hillsides and clay knobs and gravel knobs and we have bottoms that are wet. So we probably have a more percentage of poor ground what I would say poor to moderate type ground in our fields, like most of South Dakota does, than say when you go into some of the areas of Minnesota, Iowa, where 95% of the field is very good soils. So our soils are more similar. We have some of the productivity soil productivity capacity that the high states have in our fields, but we also have more poor ground in our fields.

Jodi:

So it sounds very much like the prairie pothole region where you've got glacial features.

Lane Bothwell:

Topography really is the driver, I think, between the good productive areas of the field, which again, I think I can confidently say that we can grow crops you know that are southern Minnesota, iowa type crop, I mean very good yields. But then with topography comes low wet bottoms and hilltops that then can show some fairly poor productivity zones. So we have the potential in a lot of areas, but with the topography that we have in a lot of our fields there are going to be some lower productivity areas.

Kurt Turner:

So a typical map for us for corn yield we will run a low of, let's say, 130 on yield, 130 bushel, up to 230 to 240 on the high end. So that's a lot of variability and we have some fields where we have the bottoms at 100 bushels. So yeah, it's a lot of variability.

Jodi:

That's really interesting and thinking about variability and like your specific cropping system. So you're in eastern South Dakota, you are in a corn and soybean system. You are in dairy country, which means there's manure applications, but you also have a lot of topography. You are in a corn and soybean system. You are in dairy country, which means there's manure applications, but you also have a lot of topography. You are in like the prime mix of gridding or zone mapping for your fields. Do you have any fields that are fully gridded, or what would you say your mixes is of like full grid versus zones. Because the reason I bring that up when I think about manure application, that is a man-made introduction of fertility and so the landscape is no longer driving the soil fertility on that, you've got how much manure you've placed over there over time as being your driver. So, yeah, what does that mix look like for you guys? Grids versus zones?

Kurt Turner:

I would say we're 99% zones. There's a few fields that we should grid and those are fields that are behind the barn, kind of fields, where the manure spreader goes out and they just head out behind the barn and when they're empty they turn around and go back, so the far end of the field doesn't get any. And those are to me, those are fields that are grid candidates. Otherwise we're mostly zones.

Jodi:

And I think back to our discussion about landscape, and I am guessing that's because your yields are so landscape driven that zones just make sense for you guys to implement it that way versus grids.

Kurt Turner:

Yep, yeah, and we have some fields we don't do variable rate on because they're really quite uniform. So we haven't done any zones on them because there just isn't any uniformity, especially when you get in some of the soils and fields around down in the Big Sioux Valley there that are completely flat. It's all one soil type across the field. And yeah, some of those we don't't. We haven't, we have not zoned out.

Sarah:

So out of curiosity and those do you usually go back and soil sample those like flat rate fields in the same place every every year. Are you still soil sampling the same point every year on those?

Kurt Turner:

Currently we're not doing that. Originally I was doing that, but we've kind of gotten away from that. If we're going to pick up changes or variability within the field, that maybe is real, I think you would miss that if you're going to go back and do the same points all the time.

Lane Bothwell:

I think, as long as they're not doing major changes again, let's be getting back to manure applications. Everything's quite consistent year after year after year. We haven't been going back to those same points. I think you know, if you're taking soil samples consistently and accurately, regardless if you're going back to those same points on those flat, consistent, non-variable rated fields, we're going to find some significant changes, whether we go back to those same spots or not. Usually they're just very consistent, Yep.

Sarah:

Yep, I think that's an important thing for the audience to know as well, because I have run into that myself right here in the Red River Valley around Halstead and in Hillsborough. It is flat, we have the same soil type for miles and it just there are times and places where I've seen it appropriate to make zones in these areas, especially for places where maybe the surface drainage hasn't always been great and you've got potholes where things have drowned out. But kind of once you get that figured out, it's flat and it just doesn't change a whole lot. So that's an interesting conversation too about where is precision agriculture? Maybe not always the right answer, or zone sampling, or precision soil sampling, I should call it. So let's ask the question how are you guys gridding the zone? You've been experimenting with this and, just from a logistical standpoint, how are you actually gridding these zones?

Kurt Turner:

pH. Those are the zones that we are trying to grid, and that way we can get and figure out where are the pH issues within that zone that need to be taken care of in the form of lime, and so for us, right now, it's pH driven.

Sarah:

Okay, the purpose, the prime purpose for your gridding the zone is pH and and remediating acid soils. You're not using it right now for phosphorus or potassium or anything any other non-mobile nutrient.

Kurt Turner:

Okay, no, the first ones we have done now, not to say that we might not do more of that in the future, but right now. So the ones that we have done. We just go out and sample for pH and that's all we're doing. And then from there we build a LIME application variable application map based on what the pHs are within the grids in that zone. So, for example, if you have a field that has a green, yellow, red zone, right, you got three productivity zones. I think, as I look back at some of last fall's samples, some of the problem zones have been green zones, some yellow, but there's more green zones than yellow zones from what I have seen. So we would set up grids within that green zone and then we would sample those grids and then, based on our pH, build a lime application map based on that.

Sarah:

And Kurt, just to ask, your green zones are usually indicative of a high productivity area, then yes, they are yes. And so you're actually seeing these issues in your area and the high productivity areas.

Kurt Turner:

Some in the yellows too, but more I would say. It's been about two-thirds green, one-third yellow.

Sarah:

Interesting.

Jodi:

Which makes sense, because when I think about your areas, so like your red zones, like we were talking about in the previous episode and this episode too, your red zone seems to be either your gravel hilltops or maybe around your sloughs Is that right? Or like what are? Your red zones, typically in your area.

Kurt Turner:

Yeah, that's typically where our red zones are and those are typically higher in pH. Okay, yep, and those are typically higher in pH, so okay.

Jodi:

Yep, and thinking about like pH, right. So if we think about like a gravel hilltop and this is not the case for every single soil, but typically when we think about the prairie profile, you've got like an A horizon, your nice beautiful dark organic matter level, and you've got like a BK horizon, which is again very common in prairie regions. But that BK horizon, that next level down, typically has an accumulation of calcium carbonate and so on our hilltops. Typically, you know it's an area of really high erosion, that A layer is probably gone and we might be hitting a higher level of calcium carbonate and probably getting higher pHs on those hilltops. Again, that's not always the case, right, hilltops can be made of clay, like we've mentioned before, and also sand too. That's really interesting in your area that those highest productivity zones are where you're seeing the lower pH. There are stories in North Dakota too, where that's the case, where the higher productivity areas are really where we're starting to see some of these low pH soils.

Kurt Turner:

first, yeah, we had a case where we had we actually had a. It was a fairly it was a fairly new client for us and they had a. We gridded the green zone but there was an area down in the in the corner of the field that it was very poor productivity and it didn't really make sense from a topography standpoint why that area was so pure. So we did actually sample that for pH 2, and it turned out to be the lowest pH of all the grids. And so sometimes it's not just well, we're just going to do the green. In this case we did that red spot too, because it just didn't make any other sense why it was poor productivity. But it was as we suspect. We suspect that the poor productivity was because of the pH. So that zone, if they get it limed and I don't believe it's been done yet, but in that case that area may turn into a yellow zone or a green zone if we get the pH correct.

Sarah:

So a guy has to use their brain a little bit too on this stuff. So when you run a zone sample and you get your soil test back by the zone, do you have a pH that you're kind of looking at for the whole zone to try to decide? If yeah, I should really think about gridding that particular zone.

Kurt Turner:

Yeah, four below six. Four below six pH Yep, okay yeah.

Jodi:

And when you're putting your grids together. What size are you typically putting your grids? Does it depend on how big the zone is? How are you approaching that?

Sarah:

Or how many soil samples Lane actually wants to pull that day.

Kurt Turner:

Yeah, so I call Lane and I say how busy are you anyway? But as the ones we've done so far, I've tried to try to fit the grids into the areas and so they have been in that three to yeah, I'd say, an average of three to three and a quarter acres grids is what they've been, just kind of trying to fit them in now, not saying that's how we're going to keep doing it, because we're still trying to learn too. Not saying that's how we're going to keep doing it, because we're still trying to learn too.

Jodi:

So, yep, I'm really curious, like with the fields that you have gridded so far, how variable have those grid pH levels been? Has it been pretty variable for each of those, or has each grid kind of come back to the same level?

Kurt Turner:

What are you seeing with that? Well, I would say that in the cases we've done, we're probably averaging half of the grids are low in pH and some are high. I mean, I've seen some that are, you know, 7 on pH in that same zone yeah, in that same zone. So they have ranged from, I think, 5.4 up to 7 in the zone. So there's a lot of variability there.

Jodi:

Yeah, that's always. It's so hard to think about. Okay, when you're looking at a soil test result like that is, you're trying to collect an average for the area that you're covering and, yeah, it's important to remember. You know, an average there's typically, or a median, there's half the data that's above that point and half the data that's below.

Kurt Turner:

Right, exactly.

Jodi:

Yeah, when we're looking at an average, we're not seeing the whole picture of what that value might be in that area.

Kurt Turner:

Right.

Jodi:

And for some areas, like you know, where the soil is the same type across the whole field, then that median or that average might actually represent a big majority of that field.

Lane Bothwell:

Right no that's.

Kurt Turner:

That's really interesting to hear you know what your results are and what you're seeing with that and digging deeper into that variability within your field and I have found that to me, this, this I think it helps to justify a little bit about what we're doing, in that when we find the pH areas that are low, they kind of tend to be clustered and near each other, next to each other. So I don't know, it gives me a little more confidence, I guess, in what we're doing, yep.

Jodi:

It's not like you have like a 40-acre zone and you go out and it's checkerboarded across that they're all low in pH or like every other one is low in pH. You find like clusters of where this whole 10 acre spot in the middle is low pH and the other areas around it aren't.

Kurt Turner:

Right.

Jodi:

And you find it in clusters, not just randomly across that zone.

Kurt Turner:

Correct yeah.

Sarah:

How small when you've been making your variable rate Lyme prescriptions? When you've been making your variable rate Lyme prescriptions, what are some of the smaller, lower pH areas that you've tried to address? From a variable rate, Some zones can get to be pretty big, right? I mean, I've had 40-acre zones or 80-acre zones, even if I'm on a half section, Right.

Kurt Turner:

How small? Are you able to identify those low pH areas and get a successful prescription to work to address those smaller areas within the zone? Well, I think you can probably go as small as you want, as long as the applicator knows where to go. But I tend to also round them off. I mean I tend to expand them a little bit. I tend to also round them off. I mean I tend to expand them a little bit and then if I got a cluster of two over here and maybe I got one over here, I'm going to put lime in that whole area and kind of round it out and square it off for the applicator.

Lane Bothwell:

Logistics is probably one of the biggest factors that maybe comes into lime application. The biggest challenge I think we have with a lot of our growers is liming is very different than fertilizer, the attitude and the way you know. It's a whole different process and fix right. So we had to find a way to get our growers to really take liming and pH seriously, our growers to really take liming and pH seriously. And high cost of fixing pH was not really a way to do that. So we had to find a way to, you know, make it economical as possible. So that means less work from us, which means a lower cost from us, lower acres to cover, which means less application costs and less lime to be hauled.

Lane Bothwell:

And that was, I think, our best way of trying to get guys to take this a little bit more serious, you know, but again, logistics is the biggest part of it. So we tried. We wanted to have to cover the least amount of area as possible with lime, Not just because of, you know, not only did we want to only cover the areas that needed the lime, but we wanted to make it as economical as possible as well. So our goal was to cover the least amount of areas we could with lime.

Jodi:

Absolutely. I mean, that's why we're having this conversation in the Dakotas now, right is because it's expensive. We don't have the lime quarries like they do in Indiana and Illinois, et cetera. And speaking of that, I mean where are your growers able to get lime right now? What are their sources and what have you seen being applied for lime?

Kurt Turner:

They're getting it from the municipal water treatment plants Brookings and Watertown, brookings and Watertown. They can also go to the sugar beet plant in Renville to get lime and I think there's a place down by, there's a company down by Trent, south Dakota, that actually has a lime pit and that they mine it from.

Sarah:

I didn't know that from.

Kurt Turner:

I didn't know that. Yeah, so there's some sources around, but the sources are very limited, so it's kind of a battle to get it to, because the municipal water treatment plants are only doing so much and beyond that. If you're hauling it beyond that, well then it just becomes so expensive that guys don't want to do it as it is. You know, you talk to guys about liming who've never done liming before and their eyes just roll in the back of their head and they immediately change the conversation. How about those jackrabbits?

Sarah:

Well, you know what I'm going to say to that Kurt. How about those bison? Yeah, that's right. Well, you know what I'm going to say to that Kurt. How about those bison? I'm sorry, I had to get that in?

Kurt Turner:

Yeah, so anyway, it's a bit of a challenge to get them interested as well. So there's different ways guys are applying it. Some have hired somebody to variable rate, other guys they'll haul it themselves. And I know we had a grower a few years ago that had some fields Actually there was multiple fields, multiple zones. It was green and yellow in some fields that were low in pH, so he hauled the lime himself and he got his manure spreader and he went out and spread it himself. So that's a pretty economical way of doing it too, and that's a conversation a person can have with their clients about the economics of things. Sometimes it might be cheaper to spread lime in a larger area than they need to if they can do it themselves. And so those are all conversations that we have with guys, yep.

Jodi:

So how many years have you guys had Lyme applied in your customers' fields? How long has the longest Lyme application been since application?

Kurt Turner:

Four or five years, I would say.

Jodi:

And are you seeing improvement in that pH since application?

Kurt Turner:

Yeah, there's definitely been some improvement. It seems like it takes a couple years for that pH to adjust back, but yep.

Sarah:

So, logistically, I just have a couple of questions. So, Kurt, when you're setting the maps up in ADMS, generally, when we're merging grid results, you need to have grid points and you need to have a boundary of some kind.

Kurt Turner:

Yep.

Sarah:

And so are you. How are you doing that? Are you actually like taking out the boundary, like creating contour polygons and then taking that boundary out or that polygon out, and then that becomes the boundary for you? Or how are you working that?

Kurt Turner:

Well, yeah, creating contour polygons based on the soil testing map, where we have the different zones are actually colorized. So you end up with well, of course, the way we soil sample is for nutrients is we use a five zone map, but we only sample three, and so this is the other thing I guess I'm still kind of playing with or have to work through. Do I convert that into a three zone and then make the contour polygons, and then I've got a boundary right, I've got a boundary for the yellow zone, so then from that I create grids.

Sarah:

That's really fascinating. So that's the logistics of making that happen. And then my next logistical question is actually for Lane, as far as it goes for the actual soil sampling. You know, when I've given presentations on gridding and the cost difference and the labor intensity of gridding versus zones, it's a pretty big difference if you were going to just grid an entire field. So, Lane, have you gridded an entire field yourself ever?

Lane Bothwell:

Have I gridded the whole entire field? Yes, by myself. No.

Jodi:

As podcast listeners, you can't see this, but Kurt is laughing, and rightfully so.

Sarah:

I have gridded an entire section by myself. Before that was, it was actually in two half sections. I will say and it's a lot. It's a lot, it's very labor intensive, and so can you tell me a little bit about what you think about the labor and the cost savings of doing gridding the zone type situation versus gridding an entire field to glean the data that you're looking for glean?

Lane Bothwell:

the data that you're looking for. So I guess, on the cost part, I mean of course we're grading a smaller area and we're you know, which would probably mean we're taking less samples, which means the cost of that is a lot lower. I believe we set it up differently on how to charge. Instead of a per acre cost, it's what's it costs us per grid which then gets passed on to the grower. So the less grids we have to take, of course, the less that it's going to cost to grow. But as far as labor intensity, again, my attitude towards grids becomes very different when I know the value of the grid that I'm taking. So gridding whole fields in our area for productivity wise purposes, my attitude towards that would be very poor and I'm not having a lot of fun. But knowing I'm going out there and that I'm gritting a smaller area and it's for a purpose that I know is going to have some value to the grower, you know that makes the day a lot better and we can get it done a lot faster and again, the value of that is a lot different than gridding the whole field.

Lane Bothwell:

We are not set up very well to do grids. You know we go to do it, do it on a four-wheeler. You guys know my attitude on that. Doing stuff on a four-wheeler early spring, late fall, that's not a lot of fun. That takes time, you know. And then we're using hydraulic probes and pickups. That's not a extremely fast process when you're. There are better ways and ways to set up units with faster machines, but we're just not set up for it really. So just being able to have to do less grids, less acres, the cost of it for our growers and the logistics on our side, we can actually get it done and, again, that value that we're bringing in is worth it.

Kurt Turner:

You take a typical, let's say, 100 acre field and you're going to do two and a half acre grids. That's 40 grids, right, and the way we're doing it with kind of targeting pH, so if I grid the yellow zone I may only do 12 to 15 grids rather than the whole 40.

Sarah:

It's a huge, I think, a huge time savings for us and some cost savings for the grower yeah, are you soil sampling zero to six, six to twenty four on this grids, or are you only doing?

Jodi:

zero to six, just a zero to six yeah anybody that's done grids, I think would agree that going from 40 to uh 12 is a it's amazing that's a win for everybody, it's a w W.

Kurt Turner:

Right.

Sarah:

Kind of like the bison.

Kurt Turner:

The other thing is we're still learning, and a year from now, our attitude and what we're doing might be totally different. We're just still an experimental stage here, but so far that's what we're seeing, yep, and I think that's something else that's really important.

Sarah:

So far, that's what we're seeing, yep, and I think that's something else that's really important. Who would have ever thought that, when it seems like the debate has always been grids versus zones, that you could combine them and just be more efficient and get better data for the grower to make really good, informed decisions? But along the way, we're just learning. I mean, precision agriculture does not look like what it did, Kurt, I would imagine, at the beginning of your career, and it's probably going to keep changing, and so it's okay to keep learning and keep adapting things until you figure out what really is how you want it to be. But boy, it sure seems like this is a great way to be going forward and getting growers a really nice data set to be working with and address some real issues in a very efficient way.

Lane Bothwell:

Like you said, addressing those issues. I mean, we've seen this in the past where you get your zone results back and, yeah, there's a zone that is low in pH. So then you go to the grower and you have a conversation. You have this zone that's pretty low in pH. Okay, well, what are we going to do about it? I don't know. Let's just spread lime on that zone. So that's kind of where maybe it started right and then it's well, maybe, maybe we only need to spread lime on parts of the zone.

Lane Bothwell:

Well, the only way that you're going to figure that out is by breaking that zone down, and of course gridding is is the best way to figure out pH differences. So we just kind of evolved into doing that.

Kurt Turner:

Yeah, and even before you do grids, before you start setting up grids and doing grids, the conversation with the farmer is how is he going to apply it and so forth. Because if he's going to haul his own lime, if he's going to use his manure spreader, there's probably no point really gridding it, because he can probably do the whole zone cheaper than us gridding it and getting a variable spread and all that stuff. It's not a system I would say that everybody's going to utilize.

Jodi:

There needs to be consideration of logistics and the specific grower and both of your time to figure out what the best fit is.

Sarah:

But it's precision agriculture, that's the point. Be precise with what the guy needs. So if one guy needs this, great, let's roll with it. If another one doesn't, let's not.

Kurt Turner:

It's the concept of precision agriculture.

Jodi:

This has been fantastic. It's so great to hear from you guys in South Dakota, pretty much pure corn and soybean cropping system how you guys are addressing these pH issues, and I think this has been a really insightful conversation that's going to be really helpful to growers not only in South Dakota, north Dakota, but probably across the country, and so thank you guys so much for sharing your insight on this and your experience. It's been invaluable. So thank you guys again for your time.

Sarah:

Thank you to the gentlemen at Ag Genesis, Kurt and Lane, and with that here at GK Technology we have a map and an app for that in the fields again. No, I can't wait to get in the fields again.