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Subsurface tile drainage is an essential no-till water management practice on poorly-drained soils. Eileen Kladivko, a Purdue University agronomist, helped conduct a 35-year drainage research study at the Southeast Purdue Agricultural Center (SEPAC) on high silt, low organic matter, poorly-structured soils that were not tile-drained prior to the 1980s.

In this No-Till Farmer Podcast, brought to you by NewFields Ag, the No-Till Innovator unpacks the eye-opening results and explains how drainage over time dramatically impacts no-till yields, cover crop growth, water quality and more.

         
           

         
           

The No-Till Farmer podcast is brought to you by NewFields Ag.

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Full Transcript

Welcome to the latest edition of The No-Till Farmer podcast. I'm John Dobberstein, senior editor of No-Till Farmer. In the latest edition, brought to you by NewFields Ag, Eileen Kladivko, a Purdue University agronomist, shares the results of a 35-year drainage study at the Southeast Purdue Agricultural Center on highest silt, low organic matter, poorly structured soils that were not tile-drained prior to the 1980s. The no-till innovator will unpack the eye-opening results and explain how drainage over time dramatically impacts no-till yields cover crop growth, water quality, and more.

So, today I'm going to talk about drainage and I'm going to try to convince you, but I'm thinking since you're in this room with all these other choices, you already know that drainage is maybe important for no-till and cover crops, but that's part of what we're going to talk about is some evidence for drainage and why it's important and what we have learned about drainage over the years. I am going to talk primarily about data from my own research study, which is in southeastern Indiana. So, actually not too far from here, but the implications from what we did are much broader about drainage in general. So, the fact that it's in one place will not limit what we've learned except in the very fine details, of course. I think the implications are much broader than just from my one site. So, drainage for the long haul.

So, you want to improve crop productivity on your farm. That's why you continue to come to conferences and workshops and interact with other farmers and conservation people and researchers. You're wanting to continue to improve your crop productivity and maybe you're considering growing cover crops or you already are, maybe you're considering no-till or strip-till or you're already using those practices and you're looking at other practices that you might use to improve soil health along with crop productivity. But maybe you have fields that look a lot like this and you go, huh, I wonder whether that affects my ability to improve soil health and improve crop productivity when I have these naturally poorly drained soils. So, I'm talking about naturally poorly drained soils, so I'm going to put that out there right at the beginning. We have soils that are inherently poorly drained that have some type of a restricting layer that's fairly shallow, that is natural that we had nothing to do with, it's not due to mismanagement on our part.

We have a fragipan or we have a claypan, or we have glacial till at two and a half or three feet deep, and the water basically gets to that level and then it builds up and it ponds and it's a high water table soil at certain times of the year, like starting about now through April for many of our naturally poorly drained soils. So, that's the soils that I'm talking about. And so subsurface tile drainage is an important management practice that we use on those soils. And my thesis to you today is that it's the first step to improving soil health if you have these naturally poorly drained soils. And it's a very common water management practice throughout the Midwest. So, why is tile drainage so important and how does that relate to what most of the talks in this kind of a conference are about, which is no-till and cover crops? And how does drainage really relate to that?

Well, the bottom line is that again, if you have a naturally poorly drained soil drainage pays, okay? It pays in a number of ways, and I'll go into more details on each of these as we go along. First of all, drainage improves timeliness of field work in the spring, drainage improves crop yields, and I'll show you some data that we have on that. Drainage improves cover crop growth. So, if you're trying to improve soil health by growing cover crops, drainage is going to help you with that as well. And drainage enables other conservation practices to work better, to improve soils. Drainage is a long-term investment, so in any given year, it may or may not be beneficial, but it's a long-term investment. So, I'm going to be talking about some specific long-term research that I've been lucky enough to be involved with almost since the first day I stepped onto the Purdue campus as a new professor in the agronomy department down here in southeastern Indiana.

So, again, not too far from where we are here in Louisville, and this is the SEPAC, Southeast Purdue Ag Center. So, you'll hear me keep talking about SEPAC, it's the agricultural research field of Purdue that's in that particular location in the state. And the research that I'm talking about was motivated by questions of farmers in that part of the state well before I got to Purdue. I just happened to come at the right time to be able to be involved in this research. So, the original goals of the SEPAC's drainage studies were to take this poorly structured, very low organic matter soil, highly erodible soil, and naturally poorly drained, the Clermont silt loam and to first of all see whether we could improve drainage. I need to bring you back a little bit to the early eighties. And when was plastic perforated tile drain tubes really becoming common?

They really started to become common in the seventies. That's when farmers in that part of the state were petitioning to the state legislature to have Purdue do some drainage research with modern plastic tile drains because typically they did not tile drain those soils for two reasons. One is the water didn't move very fast through the soil anyway, and maybe it wouldn't get to the drain, and if it did get to the drain, the drains got silted in pretty quickly because there was very poor structure. And so they would basically get clogged in a short period of time. So, the farmers were asking Purdue to do some research with modern plastic drain tubes in the seventies, and when I got there in '82 was when they finally decided to do it. And so I had the opportunity to work with three very experienced researchers, two ag engineers and one soils person, and I was the by far junior member of the team at that time learning about drainage.

So, the goals were to first of all, test whether we could improve drainage, and then secondly, could we improve soil physical properties? Crusting and erosion was a big problem for that soil because low organic matter, poor structure, and could we increase the infiltration and the permeability? And of course, could we, and how much could we improve crop growth and yield? So, just the drains were installed at four spacings. So, the ag engineers wanted to know what the optimal spacing would be. They encompassed what they thought the optimal spacing would be, and we had some that were closer together and some that were further apart. The four spacings that were used were 5, 10, 20, and 40 meters or 16, 33, 66, and 132 feet. The last one, the 40 meter or 132 feet, was considered by them to essentially be an undrained control. They basically assured me, this young person, they assured me that this soil is so slowly permeable that if the tile drains are that far apart, they won't have any effect and we can assume that it's like an undrained field.

And they were mostly right, not perfectly, but mostly right. The tiles were installed at a two and a half to three foot depth. Our fragipan on that field was at three and a half to four feet. So, we needed to stay above that. And we used standard four inch plastic drain tube and no sock or filter. The arrangement of these tiles was basically in sets of three. So, we had a set of three drains that were 20 meters apart and then three drains that were five meters apart, three drains that were 10 meters apart. And that comes into play towards the end of the talk when I talk about the water quality aspects of the study that we did. All right, so if we're going to consider drainage, it's not just a yes or no that we're asking. First of all, we're asking yes or no, but if we say yes, then we want to know, well, what's the drainage intensity that we need?

How close together should we put those drains to be most effective for crop yields, for economics? So, we're designing these systems differently based on how fast we want to remove the water. So, if you're growing vegetables or some other high value crop, you're going to place them closer together, because you want to get rid of that water faster. If you're growing corn and soybeans, not quite so intense. And so typically what we're designing based on is how close together to put them and what depth to put them. And most states in the Midwest, because we have a lot of soils that require drainage, most states have some kind of guidance to get people started. Soil properties affect the design. How permeable is the soil, where is the restricting layer and so on. So, the drains were installed in 1983. Actually in February and March, it was a dry February and March. Turned out to be a dry year, a drought year.

And so the drains were installed using laser guided equipment. Our main drain was parallel to Highway 50 for those of you who might know the North Vernon Seymour area. And then we had the laterals that went up into the field. We used wheel trencher machine to put in the laterals. And because this was an experiment, we wanted to be able to tap into the drains and measure their flow and measure chemicals in the drains. So, the laterals emptied into a metal culvert where we could sample them, and then from there they were routed to the main drain, which then went out to the ditch.

All right, so now let's take a look at some of those things where I said drainage pays. Let's take a little bit harder look at those, more detail. So, the first thing is that drainage improves timeliness of field work. So, this study ended up being like 36 years or so. During the first 10 years of that study, we were doing tillage. That was the standard management practice in that part of the state, we did spring chisel tillage because if you tilled in the fall, it didn't really do anything because the soil melted together over the winter. So, spring chisel tillage was the standard, and we were growing continuous corn because the first question had been, does drainage pay for corn? Okay. So, during those first 10 years, the different drain spacings were chiseled and planted when the soil for each treatment was ready. So, Don Beely, our farm superintendent, went out on April 15th, whatever date it was that year, looked at the field, decided whether the narrow spacing, the five-meter spacing was ready to till or not.

If he said it was ready to till, they tilled it today, planted it tomorrow. He also looked at the next spacing, the ten-meter and said, is this ready to till or not? If it wasn't, then he went out tomorrow and did the same thing. So, every day basically going out and seeing whether the next treatment was ready to be tilled and then planted. Well, of course what would happen in some years is the five-meter was ready today, the ten-meter was ready tomorrow, and then it rained. So, the twenty-meter was not ready the next day, because it got set back again. So, what that meant is that in that first 10 years, the undrained control plots were delayed between one to 15 days compared to the narrowest drain spacing. So, some years was a dry year. That week in April it was dry, everything dried up, you could get everything planted within a week.

Other years there were numerous rainstorms and it got delayed. So, somewhere anywhere between one and 15 days. So, of course for farmers, more timely access to the field is a major benefit in most farming operations. I can get in today, we're going to get a rainstorm tomorrow, that's really of benefit. This is just one aerial photo to kind of show that first obvious question. Does drainage work? Does tile drainage work on this soil? And this is illustrating very clearly, yes. You can see this is actually an aerial photo from the end of February, but you could see the lighter gray colors, meaning that the soil has been drained. And he superimposed the blue lines on there to illustrate where our tiles were. And you could see where our tiles were close together. The soil has definitely been drained. Where we had the undrained control, where you see no tile, you can see it's still dark, so the soil is still quite wet. So, the first question, does the plastic perforated drain tube work on this soil is clearly answered, yes, it does. Okay. It does drain the soil. It's effective in removing excess water.

All right. This slide has a lot of data. I'm just going to walk you through a few examples of it. I do have some extension publications, which I'll have a slide at the end that points you to where you can find those if you're interested in more details. So, the first thing is that the effects of tile drainage, of course, just like any other management practice that we have are going to vary from year to year. So, on average, over that first 10 years, we had a 10 bushel benefit of the narrow spacing compared to the undrained control. 10 bushels on average over the 10 years. I was very disappointed, but one of my mentors told me that actually he told me after the drains were installed, before we even had the first bit of data, he said, "Now, Eileen, you understand we have just started a long-term drainage project. You understand that the next three or four years are going to be dry."

Now I understand. Okay, so during that first 10 years, we did have two years where we had that really significant planting date difference, but most of the other years were only a few years. Most of the other years were only a few days. So, it wasn't a particularly wet ten-year period. And so we did have yield differences, but just not as much as I had hoped. If you look at some individual years, you'll see some years that have the stair step that we would've predicted, right? The narrow spacing had the highest yield and its stair step down to lower yields as the drains got further and further apart. And as we got to that situation where we said it was undrained. Other years the middle two drain spacings were the best yield. In seven of the 10 years we have the lowest yield in the undrained control.

Seven out of 10 undrained was the worst. We never had any years where the undrained was the best. So, we've had a benefit just not quite as large as we had originally hypothesized. We have bigger effects later. So, hold on. I wasn't disappointed for my whole forty-year career, just the first 10 years. Patience. Yeah, I think we've heard that. Patience. There you go. Okay. Of course, if you are growing corn, another consideration with drainage might be the grain moisture content at the time you harvest it. And so again, averaged over that first 10 years, the narrowest spacing averaged about 21% grain moisture at harvest, and the undrained control was two points higher. And so of course this is also an economic benefit for drainage that you don't have to spend as much energy in drying the grain. All right, so another aspect of timeliness is after you've planted, do you have to replant? Because then your early planting was not very timely because it didn't do any good.

So, after 10 years of continuous corn, we did change our management practice. We switched to no-till because they were having a lot of success with no-till and other parts of the farm at that point. And because we switched to no-till, we also got rid of the timeliness part of the study because it was difficult for them to be able to manage while they were doing work on the rest of the farm. And because we were no longer needing to wait until the top six to eight inches was suitable for tillage, now we just had to wait until the top inch or two was suitable for planting. We ended up just planting all the plots on the same date from this time on. So, we did not have any planting date timeliness test. But if you get it planted and it continues to be wet and you have an undrained control, then maybe you have a different version of timeliness.

And so this is one example, and we had this a couple of years where basically the undrained control, they got it planted, but it didn't make it. Okay, so then they had to replant. So, in this case, what you see in the center here is the undrained control 10 days after a second planting. So, on either side we have the drained plots and they were planted originally on May 16th, and this photo was taken about a month later, and you can see the corn doing quite fine, but the center part had to be replanted on June 2nd because there was no evidence of anything. And so now what you're seeing is that replanted corn. So, yeah, they all got planted on a timely basis, although some would argue whether May 16th was timely, but for that year, that was the best that could be done. So, it got planted on May 16th, but it didn't make it so then it had to be replanted again. So, that's obviously a big benefit if you don't have to replant.

Okay, so this was in the latter part of the experiment. So, these are some of the corn, well, they're the corn yields from 2007 to 2017, and the experiment actually ended in 2019. So, this is the last of the main data that we have to share. And we moved into primarily a corn, soybean rotation, but a couple of times we did a corn, corn, soybean. So, these are all the corn years, and you can see that there's a couple of years, 2007 and 2011 that had a modest yield difference among the three drain spacings and the undrained control. But the rest of the years had a huge difference. The undrained control was much, much lower than the three drain spacings on the order of 50 bushels or more lower than any of the other drain spacings. So, that's a pretty significant yield difference, much more like what I had hoped for earlier in the study.

And if we take the average then of the entire 35-year project and look at all the corn years, so I think there was about 24 corn years in that whole length. Our undrained control averaged 144 bushels and all of our drain treatments were in the 160s. So, clearly a much bigger yield benefit to the drainage. And this is again, averaging those first 10 years that weren't that much difference along with the later years where there was a lot of difference. So, that's kind of our bottom line on the yields. Now, I want to dive in a little deeper to look at those yields trends over the course of that 34 year period. But basically what we found is this black line, this undrained control did not have a trend with time or a very weak trend with time. And the drain treatments were all very similar and really increased with time during the last 15 years or so of the study.

So, the undrained control was close to flat. The drained treatments were increasing with time, as we would expect from just the improvements in genetics and technologies, right? I had been asked that a lot. Well, did you see the standard 1.9% corn yield increase per year over time? And the answer yes, for the drained plots, no, for the undrained plots. The soybean yields, basically there are no lines there because there was no trend with time over that. Please note we didn't start soybeans until 1994, so we don't have as many years of soybean data as corn data. This is the same data, but presented in a different way. In this case, we calculated what we call delta yield or the difference in yield compared to the undrained control. So, the black dashed line here for the corn, that's your undrained control. So, set at zero. Okay?

And then the delta yield, sorry, this is in metric units, not bushels, but the delta yield, you can see the difference in the yield between the drained treatments and the undrained control in that first 10 or 12 years wasn't that big, which we talked about. It was much bigger in that later period for the corn than it was early on. Soybeans, again, there was no statistical difference. My takeaway from that is you need drainage to reap the benefits of any other kind of practice that you're doing, improve genetics technology and other improvements. We did switch to no-till. We did start putting in a cover crop, and of course there were genetic improvements, and we didn't try to separate out how much was due to each of those things, but we did see an improvement where we had drainage. The delta yield was greater in later years. So, what we finally came up with was, well, it seems like we had soil health improvement over time because we had no-till. We now had cover crops. We had long-term drainage that the drainage system matures with time.

And so we were seeing that yield, that greater yield difference because of those treatments. But the undrained control couldn't benefit from any of that because it was undrained, it had the wetness issue and it was not improving, right? So, we used those practices, but they just weren't nearly as effective where we didn't have drainage. Basically the undrained was too wet to benefit from the improved genetics or any of our other practices. And again, we did not try to separate out how much of that yield trend as genetics and how much of that yield trend was because we now had cover crops and no-till. Drainage enables improvements in other areas to be felt to be realized. Whereas lack of on a soil that needs drainage, you're just not going to benefit. Okay, we'll get to that for soil physical properties and earthworms in a little while. The soybean yields, I don't have a good explanation for it, but we basically found no significant difference in soybean yields.

The average over all the soybean years from '94 to 2018, basically no difference. Michael Langenmaier in our Ag Econ department did an economic analysis and he did the gross revenue per acre, and he compared the wider spacing to the undrained control. So, the 20 meter or 66 foot spacing to the undrained control over time. And again, in the first 10 years, the blue line, the 66-foot spacing was a little bit higher than the undrained control, but not a whole lot different because we didn't have that much of a difference in yields. Whereas later on we had big differences in gross revenue. And of course, part of the up and down on these is that some years are soybeans and some years are corn. So, the gross revenue's going to be very different. Okay, so on average over the entire experiment, it was about $60 per acre, average difference in gross revenue where we had the drainage versus where we did not.

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Switching gears a little from cash crop yields to soil conservation practices that you folks might be doing or contemplating doing. Drainage improves cover crop growth. So, we started using cover crops after the first 10 or 12 years, and it varied. The cover crop that we grew varied based on the year. This particular year we were growing cereal rye and we were going to be going into soybeans, and so May 13th, if you look at the tiled plots, you can see a good stand of cereal rye, looks like pretty good growth. We sampled 3,100 pounds of above ground biomass per acre, and then they terminated it to plant soybeans the next day and great growth. The untiled area, so this was that undrained 40 meter spacing. We had a good stand, right? So, it's not like we didn't get it established. You can see we've got a good rows and good spacing of plants, but they're just kind of puny, right?

They're just not growing very much. And they had less than a fourth of the amount of biomass where we had the tile drainage. So, the bottom line of that is, again, if you're planting cover crops, you're doing it for some reason or reasons, build soil health, take up nitrate, provide biomass. You're doing it for some reasons, and so you want it to grow. And this is basically saying if you have a poorly drained soil and you don't have tiles, it's just not going to grow very well, or there's a chance that it won't grow very well. I work with the Midwest Cover Crops Council and we have a selector tool, and certainly the fact that certain cover crops don't grow well with wet feet has been known for a long time. So, most of the time, and what I've already talked about has been the main drainage experiment, the spacing experiment.

We also had a second drainage experiment in that part of the field that had the 50-foot spacing where I showed you surface versus subsurface. That's where we were focusing on how can we improve soil. Physical properties was our major goal at that point. And we looked at chisel versus no-till. This was still pretty early in the no-till era. We looked at five what we called agronomic practices to see if we could improve soil physical properties. In this case, CC is not cover crop, it's continuous corn. So, continuous corn only was our control. And then we had either a winter cover crop of wheat or cereal rye depending on the year or a winter cover crop of the annual ryegrass or dry manure chicken litter from Rose Acres egg production down the road. And we had a three-year rotation of corn, wheat, and then a orchard grass, red clover meadow. These were 100-foot plots. So, we hand broadcast the seed into the standing corn. They were small enough that we could manage that. So, I'm going to make two major types of points of the corn yield.

So, this first, these percentages here are the increase for tiling. So, the blue is tiled, the red is untiled. So, for continuous corn, we had a 12% greater yield for tiling compared to the untiled control. For all of our other agronomic management practices, it was about a 20% increase. So, that's one way to look at the data that where we had the tiling, we got more benefit from our agronomic practices than where we just had continuous corn. The other way to look at this is to just look kind of straight across at the blue bars. Those are the tiled. Our agronomic management practices were equal or greater in yield than our continuous corn, whereas where it was untiled, our yields were equal or lower than our continuous corn. So, again, those practices didn't work very well or did not work nearly as well where we didn't have drainage versus where we did. So, our average continuous corn yields were somewhere between 16 and 25 bushels per acre higher in the tiled versus the untiled.

And this is what I just said. The cover crops rotation and manure had equal or greater corn yields when it was tiled, but equal or lower corn yields when it was not tiled. So, this is kind of my bottom line, and I talked to a number of different groups including lay groups. And so I try to stress that a good drainage system really is necessary as the first step to improving crop yields. And the agronomic practices alone, they're not likely to make up for an inadequate drainage system. And again, this is where a number of people don't necessarily understand our terminology of naturally poorly drained, naturally poorly drained, meaning a high water table soil, natural. You can improve permeability with cover crops and no-till, but the water still has to go somewhere. And so basically we're saying in order to improve that soil health, you need to have an adequate drainage system first.

Some of you know I've worked with earthworms, earthworm populations were generally higher. This study as well as many others that I've been involved with where we had no-till versus chisel where we had tiled versus untiled, where we had some of these other practices versus a control. And soil physical properties, we measured certain things like aggregate stability that you hear a lot of people talk about, and it was generally improved by cover crops and rotation as well, particularly where you had the drainage versus where you didn't. This was a very interesting study. So, we had a lot of these night crawler channels in the narrow drain spacing, but in the undrained control, there were very few, if any. So, over the course of time, and these were not little babies, I was amazed at how fat and happy they were. Now, they were smart enough to be down at the bottom of the pit, and we were stupid enough to be up at the top of the pit on this hottest week in July.

But that's okay. So, the earthworms are also going to be very much affected by having adequate aeration. All right, so drainage pays. It enables other conservation practices to work better, and it's a necessary first step. I do want to have a little time to talk about water quality. So, switching gears, water quality, nitrate leaching. We study nitrate leaching into the tile drains, as you know, is not held by the soil. It's an anion. It's not held by cation exchange sites. It's not adsorbed to organic matter. It moves with the water that goes down through the soil profile. Because we implemented cover crops and we also changed our fertilizer practices over the course of this long-term experiment, we had, without going into all the details of our management, we had high fertilizer, no cover crop, tillage. We had high concentrations. The red line is 10 parts per million. That's the drinking water standard.

We had concentrations between 20 and 35 parts per million at the beginning of our experiment, which was typical for the time throughout the Midwest, but pretty high. Then we started changing the fertilizer rate. And then when we went to a corn, soybean rotation, we could change it. We could reduce it even more because now we had soybeans in the rotation, plus we started using a cover crop. And so we ended up with having our concentrations basically at or below 10 parts per million consistently once we changed all of those practices. So, we have the ability to reduce those concentrations, and then we calculate, well, how many pounds per acre do we lose? So, I'm illustrating three time periods. This is the early time period with high fertilizer, no cover crop. And you can see this is nitrate-nitrogen load in pounds per acre per year.

The first thing to think about is if you bring drain spacings closer together, you do that so that you can remove more water faster, right? That's why you put in drains closer together is because you want to get rid of water faster. Well, if you do that, then whatever the water's carrying with it is going to come out, more of it's going to come out as well. So, that's what we have here. The yellow is the wide spacing, and it lost about 23 pounds of nitrogen per acre per year during that early period. And by the time we got to our narrowest spacing, were up at 44 pounds of nitrogen per acre per year lost out the tile. Again, typical for the Midwest at that time, but a big loss to the farmer as well as a water quality issue. I reduced my fertilizer nitrogen.

I started using a cover crop. I got a corn, soybean rotation instead of continuous corn. So, the limitation of my study is I can't tease out how much is due to each of those practices because I only had two replications. I couldn't split it all up. But I can show you data from Iowa where they have cover versus no cover, and it's very clear, it's very common that people in the Midwest when they implement cover crops will reduce those nitrate concentrations and those nitrate losses by using cover crops. And that alone usually reduces the nitrate loads in half, usually. Because essentially you have something growing during a time of year that we typically don't have anything growing, and it's taking up any nitrogen that's either leftover from fertilizer or that is released by organic matter decomposition.

So, this is what was a little disconcerting to me, was that in the next 15-year period, we still had the low concentrations. We still had the low concentrations, but we had five inches more rain, and almost all that rain came in the winter, which is when we have drainage, not in Minnesota, but in Indiana. We have drainage in the winter primarily. So, we increased our losses compared to this period, and we have that stair step effect. So, if I'm putting tiles in closer together, I'm going to lose more water and I'm going to lose more nitrate. And so this is my plea to farmers that I'm a big proponent of drainage. Where you need drainage, you need drainage.

But if we're going to start putting tiles closer together, which a number of folks have, when economic times are good, then we also need to increase the intensity of some other aspect of our nitrogen management. Cover crops is one of them, but you see here, I had cover crops as well. So, cover crops do not mean we're not going to lose any nitrate, but we're going to reduce it compared to what it would have been. So, my emphasis is if this is what I'm losing with cover crop, if I didn't have a cover crop, it would be way more like what I was losing early on.

Well, that's it for this episode of the No-Till Farmer Podcast. We'd like to thank Eileen Kladivko for this revealing discussion about subsurface drainage and its importance to no-tilling on poorly-drained soils. We also want to thank our sponsor, Newfields Ag, for helping to make this podcast possible. A transcript of this episode in our archive of previous podcast episodes are both available at notillfarmer.com/podcasts. For Eileen and our entire staff here at No-Till Farmer, I'm John Dobberstein. Thanks for listening. Keep on no-tilling and have a great day.