Here we are in 2025. Today on the Nutrient Management Podcast, our panelists talk about how the practice of nutrient management has changed over the last quarter century. How have precipitation levels - and perceptions about precipitation - changed? What came before the current Maximum Return To Nitrogen management model, and what did the change address? How has U of M research contributed to sulfur nutrient management understanding? How has awareness of ground and surface water quality evolved? Finally, how has tech changed (or not changed) the practice of fertilizer management over the last quarter century? This and much more on today's show.
Guests:
Daniel Kaiser, Extension nutrient management specialist (St. Paul)
Carl Rosen, Extension nutrient management specialist (St. Paul)
If you have questions or comments, please email us at nutmgmt@umn.edu.
Support for the Nutrient Management Podcast is provided by Minnesota's fertilizer tonnage fee through the Agricultural Fertilizer Research & Education Council (AFREC). Learn more at MNsoilfertility.com.
Chapters
- Welcome, and introductions
- Precipitation has increased. How have each of the 4Rs been affected by this increase in precipitation?
- The Maximum Return To Nitrogen rate model (MRTN) wasn't around 25 years ago. What prompted that change?
- How has UMN research contributed to sulfur nutrient management understanding?
- Water quality awareness is top-of-mind in 2025. What do we know today versus 25 years ago?
- How has technology affected - or not affected - fertilizer management over the last quarter century?
- The Nitrogen Conference and Nutrient Management Conference both are right around the corner. Register today at z.umn.edu/2025conferences
Here we are in 2025. Today on the Nutrient Management Podcast, our panelists talk about how the practice of nutrient management has changed over the last quarter century. How have precipitation levels - and perceptions about precipitation - changed? What came before the current Maximum Return To Nitrogen management model, and what did the change address? How has U of M research contributed to sulfur nutrient management understanding? How has awareness of ground and surface water quality evolved? Finally, how has tech changed (or not changed) the practice of fertilizer management over the last quarter century? This and much more on today's show.
Guests:
Daniel Kaiser, Extension nutrient management specialist (St. Paul)
Carl Rosen, Extension nutrient management specialist (St. Paul)
If you have questions or comments, please email us at nutmgmt@umn.edu.
Support for the Nutrient Management Podcast is provided by Minnesota's fertilizer tonnage fee through the Agricultural Fertilizer Research & Education Council (AFREC). Learn more at MNsoilfertility.com.
What is UMN Extension Nutrient Management Podcast?
Welcome to University of Minnesota Extension's Nutrient Management Podcast. Each month we bring you the latest research in nutrient management for crops and how you can incorporate the latest tips and best management practices to your farm.
Jack Wilcox:
Welcome back to University of Minnesota Extension's Nutrient Management podcast. I'm your host, Jack Wilcox, communications generalist inside of Extension. We're now in 2025, and we thought it'd be interesting to take a look at some of the more sizable changes that the practice of nutrient management has gone through in the last 25 years. We have 5 panelists here with us today, and they have experienced these changes firsthand. Can you each give us a quick introduction?
Dan Kaiser:
This is Daniel Kaiser. I'm a nutrient management specialist at the Saint Paul campus at the University of Minnesota.
Carl Rosen:
Hi. I'm Carl Rosen. I'm also a nutrient management specialist. I've been here for 40 years, so I've got the 25 years plus a little bit more.
Jeff Vetsch:
I'm Jeff Vetsch. I'm a research supervisor at at, Southern Research and Outreach Center in Waseca, and I don't quite not quite to where Carl's at, but I'm not too far behind.
Brad Carlson:
Brad Carlson. I'm an extension educator out of the regional office in Mankato, and, my extension time is 30 years, but I was looking at my HR web page the other day. I think my first date of being an intern at Waseca was in May of 1990. So that, that puts me at 35 overall.
Fabian Fernandez:
And I'm Fabian Fernandez, a nutrient management specialist based in the Saint Paul campus working on nitrogen management for corn cropping systems and environmental quality. And I am a transplant to the Midwest, and to the US. I I grew up in the Pampas region of Argentina, which is kind of like the Midwest of of Argentina, but, I've been in the Midwest for over 22 almost 23 years now.
Jack Wilcox:
Jeff Vetsch let's start with you. Precipitation has increased and perceptions about precipitation have changed. That means that in fact, each of the 4 r's has been affected by the increase in precip.
Jeff Vetsch:
Yeah. Exactly. You know, when we look at, here in Waseca, we have a 114, 15 years of other records at the research center. So we're kind of a good place to take a look at this, and we've also been kind of the the center stone or the the key area for increased annual precipitation. We go back about 50 to 60 years.
Jeff Vetsch:
We were used to be around 30 inches of annual precipitation from our 30 year normal calculations. We're now nearly 38 inches in our last 30 year normal period, which runs from 1991 to 2020. But, you know, annual precipitation alone, it affects the amount of tile drainage in fields, the need for tile in marginal fields, things like that, but also a recent study or a recent analysis of our precipitation patterns have shown how the southern third of the state or southern quarter of it when we break it down into quarters is really getting the wettest or wetter, and it's primarily in the spring. That includes southeast Minnesota counties, south central, and southwestern. And we think about the factors that drive nitrogen loss.
Jeff Vetsch:
I think that that spring precipitation, which is April through June, is probably the most important. And the thing that's changing our management perspectives and how we're managing nitrogen, Certainly here in south central Minnesota, we've seen fall applied anything is becoming more and more challenging and less and less predictable than it was earlier in my career, certainly earlier and back in Carl's days when we were when fall anhydrous and fall application in this region was pretty commonplace, and this is also affecting Southwest Minnesota as they're getting wetter in the spring. So some of the practices there that were pretty conservative and pretty successful historically are also having more challenging years.
Brad Carlson:
We did a whole, curriculum on adapting nitrogen management to climate, back a number of years ago and had a lot of different analysis done on on various climate factors. I mean, the temperature was part of that too and so forth, but we pretty much found the same thing, Jeff, particularly across the southern, the really the southern third of the state. It it was consistently wet all the way to the South Dakota border. We looked mostly at growing season precipitation and where a lot of our nitrogen BMP zones, particularly when we looked out on the western side of the state, some of that stuff was defined by climate. It's made us have to kind of relook at that because of how wet it's been.
Brad Carlson:
Really, the only part of the state that's been kind of immune to that has been the northwest. If you look at the data, the precipitation data, in the Red River Valley, it really doesn't look very different now than it did back then, and so there's probably not been a lot of change there. But the the rest of the state's seen a lot of that. You know, and the other thing that we've seen, Jeff mentioned early spring, but we've also seen a great increase in fall precipitation, particularly in South Central Minnesota. That's created some different stresses as far as the ability to get fertilizer applied, get field work done.
Brad Carlson:
The only other thing is is the physics of temperature change in the soil, is that it takes more energy to change the temperature of water than it does of air. And so when we we see the soils going into the fall wet, they're also staying frozen longer into the spring. And so that's another thing that we kinda picked up, when we did our analysis is is actually a trend to the the frost out being about a week later than it had been, maybe 20 or 30 years ago. And and, you know, obviously, that all changes from 1 year to the next, but, you know, we do tend to want to have deal on averages because there's really nothing better to go on.
Fabian Fernandez:
The other thing that I was going to mention too was in terms of the temperatures. I think most of the the changes have been, with with water, but I I think also the, the temperatures that are increasing in the winter are also impacting some of the the changes that we are seeing. You know? I think mineralization continues on longer into into the fall. That nitrogen that is mineralized from organic forms to ammonium may stay in ammonium, may even go into nitrate, but then the next spring is when we we have more potential to lose some of that if it's already in in inorganic form.
Jeff Vetsch:
Yeah. I would add to that that when we look at our data, November February are months that we've seen are have trends that are increasing for annual monthly temperature. And some of it is related to warmer highs, but some of it is related to not nearly as cold lows for the day. And that can be attributed to more cloud cover or more moisture in the air, other factors just prevailing jet stream flow. But that is certainly driving those months in particular.
Jeff Vetsch:
Our summers really are not getting much hotter, but we're seeing this tail end of the growing season, the beginning and the end, or the end or start of winter and the end of winter, definitely warmer.
Dan Kaiser:
Yeah. And being a transplant here in about 2007 I mean, Jeff, Brad, I mean, I kind of surprised me a a few questions coming in the last few years about nitrogen loss from December rainfall events. And, I mean, I assume that you kind of look back, especially if we look at, the winter of 20 3, 24 having, tile lines flowing for longer. I mean, it's just something that just didn't really happen before. So it's just kinda one of the things that get start getting into more questions now in the fall, particularly with fall nitrogen applications in terms of availability in the spring just with some of the things that have been occurring more recently.
Brad Carlson:
Yeah. I think some people that know me personally know that I'm a hunter, and I've I've done a lot of trapping in my life and so forth. So one of the things I tend to be kind of in tune with is when the lakes freeze over and, historically going way back to my teenage years, early November was pretty much the time we would expect in southern Minnesota, the lakes to freeze over. The last 15 years or so, that's been pushed way into December. And so if it takes that long to freeze the the the lakes, it's also taking that long to freeze the soils.
Brad Carlson:
And so we are definitely seeing a later fall season. We're seeing things happening in the soil in the fall that didn't used to happen, you know, and all that's gonna have a ripple effect on how we manage.
Jeff Vetsch:
And to elaborate on what you said, you know, I we we've got the drainage study here at Waseca since the the mid to late seventies. And, historically, I would say maybe 1 out of 10 years, we would see some tile flow in the winter months. And when I'd say winter months, you know, probably either in either in December, January, or mid February up to mid late February. Typically by late February, it's not unusual to see tile flow, but usually in the past, those events were usually associated with wet falls that had a lot of early snow cover that protected the soil from really freezing to great depths. But in the recent years, especially 23 winter 23, 24 that you mentioned, it was a bare winter, and it was just that mild that we just did not see the soil freeze to any significant depth throughout most of the winter, just maybe for a week or 2, and that was it.
Jeff Vetsch:
And it was very shallow. So, yeah, it it that is a really unique change, and it's probably much more typical of central Iowa or the, you know, Ames area than it is here in southern Minnesota.
Jack Wilcox:
The maximum return to nitrogen rate model or MRTN wasn't in place 25 years ago. Nutrient management functioned under a different system. Fabian, walk us through that change process.
Fabian Fernandez:
The MRTN calculator approach came about in 2,005. That was right when I was starting as an assistant professor at the University of Illinois and Illinois, Iowa. They were kind of the the 2 states that push this quite a bit, and then, of course, many other states in the Midwest also were part of this this work. And so prior to that time, what most people were using was a yield goal approach, kind of a factor multiplied by the yield that you expected, and that was, what you would apply for nitrogen. The impetus behind looking at some other ways of of of, recommending nitrogen rates was that, when you plotted the amount of nitrogen and the yield that you needed, it was just there was no relationship.
Fabian Fernandez:
It was kind of like a gunshot pattern, all over the place. And so that's where the researchers that were first involved, and I was not involved in the first in the first part, of of the development of this, approach. I came in right at as it was being put in place and, being used as a guiding system across many of the states in the Middle East. The impetus was to to do that change because there was no relationship, and, there was a lot of research done to to look at this relationship of, okay, how how much nitrogen you need to optimize those those yields. And then the other part too is with fertilizer costs going up.
Fabian Fernandez:
And one big change I think that has come about in the last 25 years or so is the fact that corn prices are tied to energy prices more because of ethanol. And so with that, it became important to start looking at some economic variables. And so this calculator was kind of the first time that, as a region, we were starting to look at, okay, corn prices, nitrogen prices, and finding a relationship that we would not be looking at obtaining the highest possible yield, but looking at the most economic yield. And, basically, the approach is to apply enough nitrogen that the increasing yield that you get for that last pound of nitrogen pay for itself. If you're applying nitrogen that doesn't increase the yield sufficient to pay for itself, then that's where you will cut it off.
Jeff Vetsch:
One thing that I would add to that, Fabian, and is, you know, I was involved in a lot of these early years of collecting some of this data as a as a assistant scientist here at the, not only the Southern Experiment Station, which is now the Southern Research and Outreach Center, but also at nighttime as an undergrad on campus working for different faculty in the department. And when they looked at that data, what was unique is that this economic return or the MRTN approach was also not just here in Minnesota, but in other states also seemed like a good environmental, you know, compromise where we saw n rates that were much greater than what was economically optimum is where we also saw a lot of n left in the soil, higher nitrate concentrations in tile drainage, higher nitrate concentrations in suction samplers, and in studies that were done all across the Midwest. And so I think that the public has to realize it's not purely about corn growing corn and economics. It was also a great balance for economics and water quality and not leaving that extra nitrogen out there in the field to be lost.
Fabian Fernandez:
Yeah. That's that's a really good point. And if you look at the nitrogen applications historically, you know, 50, sixties, it kind of really ramped up, increased quite a bit. And I think at that point, it was probably kind of a 1.2 per bushel or so. You know?
Fabian Fernandez:
It was kind of like that at your certain up to a certain point, and then, the yields really started to increase substantially. If we were using this approach today, if you're yielding 300 bushels, there certainly, you don't need 300 plus pounds of, you know, nitrogen to get you that yield. So that was the other part is that the yields, because of a lot of the genetic improvements, have been improved substantially. They are they keep increasing every year, but it doesn't mean that you need the same amount of nitrogen as you did back with all hybrids.
Carl Rosen:
And I just wanna emphasize, this was not just a Minnesota model that we used. This was a regional model. There were at least 5 or 6 states that initially were involved, and there were many meetings up in Northern Minnesota in the beginning, in the spring where it was discussed, for for many years before we we switched over.
Fabian Fernandez:
If I remember correctly, I think I think some of the first discussions on on this approach started in Northern Minnesota, Marcelin, in the conference. Did.
Carl Rosen:
At the Marcell conference, that's where it all started. And there was a lot of discussion, and it it was basically, based on what you said, there was really no good relationship between yield, the nitrogen rate, and and the yield goal. And so something else had to be done, and taking the economics into it was, I think, a step forward because, and as just Jeff mentioned, if you follow that model, you're not only going to be more economical in the use of nitrogen, you're also going to be more efficient and less, susceptible to losses.
Fabian Fernandez:
In the world of nitrogen, with all the variability that is out there, one of the things that I look at the most and that I feel most confident about is when I see a certain pattern being fairly stable throughout all the projects that I have. And this is one that I've seen that consistency in in different kinds of ways that you measure, environmental impact, whether it's residual nitrogen or whether you're actually looking at, losses is where you apply that economic optimum. You will be losing some nitrogen to the environment, but the the footprint of that, environmental impact is way lower than if you go above that MRTN value. And so it it does help with both the the economic, the production side of things, as well as the environmental aspects.
Dan Kaiser:
And I I mean, just to kinda not get completely lost on this. I mean, you look at about 25 years ago. I do remember I mean, really what spurred a lot of this was just large increases in the price of nitrogen, which before that time, nitrogen had been relatively cheap. So I think when you start looking at it in terms of the the recommendations, I mean, there really wasn't a whole lot of emphasis in that. It's it's the economic side until we started seeing I mean, I mean, if I remember right, I mean, anhydrous was, I don't know, Jeff, Brad, if you can remember, about a1000 a ton or so it was pretty high if you start looking at that.
Dan Kaiser:
So that spurred a lot of this on was just trying to get a better way to do this, and I guess the the thing I really like about it is the fact that it's a database approach. So we're using the real world data where you start looking at a lot of these these yield goal based systems. We're we're doing a lot of assumptions just based on certain things. And if you look at, you know, a lot of what we term to be NUE or that pounds of N per bushel, you see a lot of variation that it's the consistency of it becomes an issue, and I know there's a lot of pushback from growers when it comes to variable rate nitrogen that the MRTN really isn't, anything that we can use widely to really fine tune things, but it just gives a good starting point. And I think that's really if you look at it, really the main goal really of that is to give you the starting point to know you to where to kind of manage around.
Dan Kaiser:
Then, I mean, we can talk about maybe technology later, but then it's looking at kind of what we can do in terms of technology. Because really, I mean, nitrogen, there's just really no perfect system with it. If you look at it with p and k where we have soil tests, where we can do a risk assessment before we apply the fertilizer, you know, nitrogen to some regards, we might, but it's it's just not a real perfect system.
Brad Carlson:
You know, another aspect of this that that was kind of stressed at the time we went to the system as being somebody who was somewhat involved with the the rollout of this was that that it wasn't just simply a matter of that we had some different recommendations from one state to the next because we expect that. There's differences in soils and there's differences in climate, but really the different states, a lot of them were actually using different methodology for determining their their nitrogen application rate. So if you came about things differently and then came up with a different number besides, it was starting to to draw a lot of questions from from not not even probably so much farmers as Ag professionals saying who's doing this correctly. So I think it was very valuable that the the states in the north central region all decided to use one method. We do see different recommendations, you know, higher nitrogen rates as you go south where there's less organic matter in the soil, higher nitrogen rates as you go east as we see higher amounts of precipitation.
Brad Carlson:
And, of course, there's differences in in the other application practices too. But but it really was a a way a way to kind of, make this all be done in a uniform method and be able to justify it really to as far as how you're coming about those recommendations. Another aspect of that, and and this kinda comes from my personal, role as a historian that's not official and, but but it's kind of my personal interest. When we were, putting together some of the stuff for nitrogen smart, I investigated where we were at with recommendations in Minnesota, and we did formally recommend, determining nitrogen rates, by taking 1.2 times yield, minus a soybean credit, up until 1974. And at that point in Southeast and South Central Minnesota, we went to the yield goal system, probably because there wasn't enough research data, was what my understanding was we didn't have that for the rest of the state, but the rest of that came about.
Brad Carlson:
And then then in the mid eighties, about 1982, 3, 4, somewhere about there. You know, so the extent to which people are still trotting out that 1.2, you know, remember that was, that was something we, we walked away from 50 years ago. That's a long time. In Minnesota, we always struggled with the term yield goal. In fact, we formally changed that to expected yield, somewhere around 1999, 2000.
Brad Carlson:
So for the last few years that we use that system, we called it expected yield instead of yield goal. And then, I gotta remember the exact year we came out, I think was it, was it 05, that we came out with the MRTN. So now we've been there about 20 years. We've had the MRTN method.
Jack Wilcox:
Let's switch gears and talk about sulfur. Dan, how has U of M Research contributed to sulfur nutrient management understanding?
Dan Kaiser:
You know, that's, you know, one of the interesting things, Jack. If you look at the start of my career, I never really thought I'd get into the amount of sulfur research that I had moving into Minnesota. And a lot of that just because, you know, some of the consultants up here having some that have been really interested in that for a number of years. And, you know, Minnesota itself has had a long track record of sulfur research. I mean, my predecessor, George Ream, he, did a lot of work in the past.
Dan Kaiser:
But if you, you know, you look at a lot of the data, it wasn't always really positive unless you're in some of those sandier areas with low organic matter where we tended to see more of a a response to sulfur. But, you know, you look at the clean air act, cleaning up some of the atmospheric deposition. I mean, that certainly had an impact where we're seeing, some more issues with that, but it's, you know, I think not the only factor that's impacted things. I mean, and then you look at, I think, one of the major things, and it's one thing that we didn't really talk about in the MRTN discussion is one of the bigger changes that I've seen with nitrogen rates in the last, you know, since in 2000 have been in continuous corn nitrogen recommendations because of the residue that's there. And I think that's also changed some of what we're seeing with sulfur, particularly from corn residue.
Dan Kaiser:
You get more corn residue, seeing some potential for tie up of for sulfur as well. But, you know, Jeff, I mean, you can kind of attest to this as well as I can. I mean, what's nice to have something to work on that's relatively new, although it wasn't exactly new, that we're seeing some of the yield differences that we're seeing, especially some of the early ones, with some of the the sulfur fertilization trials we had where you're getting, you know, some situations where it looks like nitrogen responses in really high returns on investment. So there's been some advantages of that. I mean, but, you know, you look at it since I've been here since 20 2007.
Dan Kaiser:
I mean, I've learned a lot too in terms of sulfur, in terms of some of the issues, and in terms of how it cycles in our in some of our systems that, you know, we've got a, I think, a pretty good understanding of things moving forward. Although, you know, we still have a lot of pushes for higher and higher rate applications from some people that just don't think we can get enough. But it's it's been interesting, you know, the early stages is kinda developing. You're trying to figure out some rudimentary recommendation philosophies for most of our fine textured soils. That's kind of when we went to the organic matter as just an indicator of the sulfur availability because, you know, the organic matter historically has been the major pool of of sulfur availability into where we're at now with a lot of the work with different sulfur sources.
Dan Kaiser:
And, know, I could go on probably for half hour, 45 minutes on a lot of this, but it's been just interesting looking at that. And then some of the data that we're getting at it, it's it's been some of the best data I've had, especially some of the more recent data. Once I've kinda figured out how to minimize, some of the the sulfur carry over and some of the sulfur in the system. Because I think that's one of the biggest things to me that growers, consultants, when you consider that sulfate is an anion, so it should be leachable like nitrate that it doesn't necessarily leach as fast. So, you know, a lot of that's one of the things I struggled kind of midway in my career here in Minnesota is finding good field sites on grower fields just because we've done a good job of educating people and that there was, you know, threefold increase in the sulfur sales early on.
Dan Kaiser:
I don't know where it is now, but, a lot more usage in there where it was harder to find, field sites that would respond because of that carryover. But, you know, Jeff, I think you can talk a little bit about that. He's you and Giles worked a lot on it at Waseca, you know, but just before I got here too, and it's it's kinda some of the interesting things kinda seeing. It's really, again, nice to have something that we at least something that it can, you know, show growers some positive benefits from something. Because a lot of the product testing work we do, it's it's it's to be a little bit of downer when you get talking about nonsignificant data.
Fabian Fernandez:
I was looking at historically where where we start seeing, sulfur deficiencies. And, actually, it was in the 19 twenties. The first, report of sulfur deficiency in the Midwest came from Minnesota in the 19 twenties, so a 100 years ago when it was first, observed. And and then the other thing that was kind of interesting as I was kind of looking through historic records and historic publications back in the early eighties during work in the late seventies, early eighties, Bob Haft in Illinois did a a project looking at, response to sulfur in the greenhouse, and he couldn't even get response in the greenhouse because there was enough sulfur in the air that you could just now get a deficiency even under a greenhouse condition. So, things definitely have changed with with sulfur.
Jeff Vetsch:
Yeah. That's you know, there certainly, Dan, the emission thing is a huge thing from the the Clean Air Act in 1990 and then the engine diesel fuel acts in 97 and then the heavy duty diesel engine rules that went in place in 2004. When you look at cumulative tons of emissions of sulfate, we're we've reduced it by 90% in the last, like, 30 years or 25 years. That's a huge number. But going back to the the research, Giles and I kinda stumbled upon it and then certainly throw a shout out to Brian Lang, who was a northeast Iowa extension educator at that time.
Jeff Vetsch:
And he was seeing it on the the rolling, hills and fields in northeast Iowa that were similar to southeast Minnesota where these eroded knolls that had lower organic matter were pale, and it was in alfalfa and it was in corn, and all you had to do was go out there and put a little bit of gypsum in those spots, and then they greened right up, and the yield responses were huge. And certainly, as you mentioned, Dan, you know, nothing makes you feel better as a sole fertility person when you can put on a treatment that costs $10 and give somebody a $100 net return. And we had some that were way larger than that. Was like you said, it was almost the effect of a nitrogen response. But looking forward at sulfur, I don't think we know everything yet.
Jeff Vetsch:
Our colleagues up there in North Dakota state are really doing some interesting things looking at the effects of saturated, poorly drained soils and the sulfur chemistry and how that determines whether or not we should be getting, we will be getting responses in some of these fields on those types of soils, even though those soils typically have inorganic sulfur compounds in the subsoil. So that's an, I think that's really interesting. And then the other factor is, as we see cover crops and maybe more soil health type cropping systems come into play, we're going to see things like cereal rye interact with sulfur again in crops that we wouldn't expect to see a response. And that's starting to show up in some of our neighboring states that they maybe have more no till and and better cover crop growth than we have, but that, again, will be something that we'll have to be keep an eye or keep a watch on and and maybe adjust our recommendations based on those types of things in the future. Yeah.
Dan Kaiser:
I think some of those, guys in North Dakota have been listening to me a little bit because I've been kinda harping on some of this poorly drained soils. You know, there is something called if you look at when we we talk about denitrification, I mean, sulfate goes through a similar process, and I think we see more of that than we think we I mean, in the past, a lot of the soil chemists really haven't really considered that important because technically, the reduction of nitrate should occur before sulfate, but I don't think it's that simple. I think it's occurring at the where we're getting lower availability in some of these poorly drained soils because I've seen it, you know, pretty widespread. But going back to 2008, I mean, it was interesting. We had a study down by Thielman.
Dan Kaiser:
It had been a grower that hadn't been applying sulfur, and he did a lot of strip cropping where he had strips of alfalfa, corn, and soybeans. It was incredible. You kinda look across all these crops and look at some of these areas that are more affected and just seeing some of the differences that were there. But, Jeff, you talked about the atmospheric deposition. I mean, I think the other thing that people don't think of either is just the lack of livestock agriculture on the landscape too, and I think that's made a big contribution as well.
Dan Kaiser:
I mean, some of this organic sulfur that more growers, more people had livestock that were was getting cycled in this ground that that's gone too. There's just a lot of contributing factors there, and there's still some things to look at. But I think we've got at least got a good understanding of the sources we have and the rates that we we're recommending, you know, kind of fine tuning them right now where I'm pretty comfortable with a lot of the data, but there there's still a little bit of work to be done.
Jack Wilcox:
Let's talk about water quality issues since they're top of mind in 2025. Brad, walk us through what you see today versus 25 years ago.
Brad Carlson:
It's been said a lot that we're now a global community and that really is kind of impacting how we approach a lot of environmental issues. Because if you go back historically in Minnesota, water quality, really amounted to people being concerned about what they were drinking and probably what the lake looked like that they spent a lot of time at. And so if we you know, look at what impacts particularly the, the, the water we can see surface water, you know, a lot of that was phosphorus based, phosphorus drives algae blooms in, lakes and rivers and so forth, and that result in low oxygen, fish kills, and so forth. And so a lot of our attention environmentally, if you went back beyond 25 years was really just phosphorus focused and because nitrogen nitrate is not a limiting nutrient in the water, we didn't really concern ourselves with that a lot because we, we attributed improvements in water quality with reductions in phosphorus in the water. And so for that reason, I don't wanna say we were irresponsible with our management of nitrogen so much as it just didn't seem like it mattered.
Brad Carlson:
And when nitrogen was cheap, over fertilizing didn't seem like it was that big of a deal. So the whole concept of insurance nitrogen, just adding some extra 20, £30 extra because it didn't cost you that much and maybe the weather would be extreme and you needed it and so forth. You know, some of that mentality, kind of developed. Well, flash forward, go back maybe about 30 years ago when issues with hypoxia in the Gulf of Mexico started to show up. A lot of the investigation that was done on that discovered that nitrate was actually creating a lot of the algae blooms and the, the other issues in saltwater in the Gulf of Mexico and the way we managed nitrogen in the Midwest, because that ultimately was ending up running down the Mississippi River and discharging into the Gulf of Mexico was having an impact.
Brad Carlson:
And so, it took an awful long time and all the issues started cropping up in the mid nineties. It wasn't really till about 2010 till we finally had a, a Gulf hypoxia action plan that was prescribing how to deal with this from the states. But, but we're there now and ended up resolving in the states and the Mississippi watershed, excluding the Missouri watershed, from developing nutrient reduction strategies to come up with targets at, at both phosphorus and nitrogen now. And so that really is impacted a lot of what we have to think about with respect to, to our fertilizer management. In addition to that, if we went back to groundwater concerns back in the 1980s, maybe earlier, it was primarily pesticide driven.
Brad Carlson:
There was a lot of issues relative to atrazine, metribuzin, some other products like that. A lot of those products have gone off the market or experienced changes in how they're used and so the pesticide in groundwater issues have really sort of disappeared over time, but now we're focusing on nitrate, it always was sort of there, but given that that we're no longer as concerned about pesticides is really the primary focus for groundwater, these days. And so, really those couple of things between surface and groundwater, has really driven a lot of our thinking as far as environmental management and and nutrients and inputs and and just overall how we are managing crops and the land.
Carl Rosen:
We talked about climate change and more precipitation. I think that's and Jeff alluded to this, but there is more tile drainage. And when you have more tile drainage, you will get more movement of nitrate through those drains. Before tile drainage, you'd have a lot of saturated soils and most of that nitrogen would actually actually go off as as a gas through denitrification. Now we have a much better environment for root root growth, we have better crops because of that, but we are more susceptible to those losses through the tile drains and that ends up in, a lot of times in the surface water, Mississippi River, and then that ends up down in the Gulf of Mexico.
Carl Rosen:
So, yeah, some of those changes in the last it's probably more than 25 years, but we still see an increase in tile drainage with with more precipitation. And so it's kind of driving driving things.
Fabian Fernandez:
Yeah. And, you know, Carl, I I was just thinking about that too, the fact that there's a lot more scrutiny on nitrogen from the environmental aspects, that we are kind of in a moving target situation because I think, management wise, we are doing better than we have ever done with nitrogen. But we the changes that we are seeing in precipitation, especially, and some with temperature as we discussed earlier, are making it more difficult to see those benefits. It's kind of erasing any any of the things that we are doing. They're kind of get erased with, you know, a few rain events that push most of the nitrogen loss.
Fabian Fernandez:
I mean, Jeff and I have looked at this in in different studies with tile drain, and you can see that about 70% of the nitrogen loss happens in, you know, a handful of events throughout the growing season early especially early in the season. And sometimes we haven't even applied nitrogen at that point, and that's where we lose a lot of nitrogen that has been mineralized and not used by the crop yet. Some may be residual nitrogen, but majority of it, I think, is through mineralization, and and we lose it. And so it is definitely a moving target. And one thing and maybe it's kind of circling back to the MRTN discussion that we had earlier.
Fabian Fernandez:
I am convinced that, you know, nitrogen rate is a very important part of it. It's not the only part. We talk about 4 hours or best management practices. You need you need to use all the best management practices. But in terms of the the rate, it's not totally important what the rate is, is the rate of utilization.
Fabian Fernandez:
If you're applying the amount of nitrogen the crop is going to use, then you're not going to lose nitrogen. Sometimes people look at, oh, you know, we are applying more nitrogen. And, certainly, when we when we look at the MRTN calculator, those rates have gone up over time. And it's not that we are doing a a poor job managing nitrogen, just adding more nitrogen to what we apply. It it has to do with the fact that that's what the crop is needing.
Fabian Fernandez:
And so if if the crop is using it, you're not losing it to the environment. And so I I just wanna make that point clear because we talk a lot about nutrient reduction, and sometimes we we tend to equate that to well, we are trying to do nutrient reduction, and the nitrogen rate calculator keeps going up over time. And it's it's not the same it's not the same thing. Right? We are actually doing some work right now trying to test some of those hypotheses of why these nitrogen rates are going up with the calculator.
Fabian Fernandez:
Certainly, one of those is climate change. We have more water. There is more movement of that water as Brad, I think, mentioned with mineralization happening later into the fall and then wetter springs, that nitrogen that would have mineralized in earlier years would have mineralized during the growing season. Now it's mineralizing before the crop is even planted, and so that nitrogen is gone before the plants are up and growing. We talked about nitrogen changes going from anhydrous ammonia to more urea.
Fabian Fernandez:
That has certainly in the last 10 years has been a huge change in Minnesota, and we know that anhydrous ammonia nitrifies a lot slower than urea. So those that change in in nitrogen source could also be part of why we are seeing higher nitrogen rates. We talked a little bit, I think, about, cropping systems with cover crops and things like that, but also another one that has been a huge change, I think around, what, 2006, 7, somewhere in there is where we started to have more of these BT corn and and, you know, the corn residue that doesn't decompose as quickly. And so that is also increasing potentially, the need for nitrogen because we have more immobilization happening for longer times. We also combine that with more conservation tillage where you don't incorporate that residue into the soil, so it takes longer for that residue to decompose and break down into nitrogen that the plant can use.
Fabian Fernandez:
So all of these things, I think, combined create that really a moving target and a difficult challenge, when we talk about water quality because, it it impacts the water quality, but it also impacts, the production side.
Dan Kaiser:
And I think you hit it on the head. I mean, with continuous corn, why we've seen it go up has mainly been the the residue situation, and I can kinda track that from 2,000 if I look at the database. You know, really, with corn following soybean, yes, we've seen it creep up, but, you know, that's mainly been just the fact that, you know, we got 4 of us on here right now that do research on nitrogen. We've been able to add more data to the in rate calculator that in the last 10 years than what could have been done before. So I think that's a lot of the change.
Dan Kaiser:
We're getting more recent data. And, you know, there is kind of something to to think about there, and that's, you know, one of the things that I really kinda push for with a lot of this, especially like the n rate calculator. Having the database, it's nice to have older data with the new because it moderates out some of these these impacts that when we have some of these what we call atypical years, but I don't know really what an atypical year is right now, but it kinda moderates some of that out. And there's there's really some danger if you're just looking at last year and then making a decision about this year with, what you're doing with nitrogen management. And that's me really the difficult thing I I see with nitrogen is you're you're generally booking your fertilizer probably in, you know, maybe in August, the year before you need to put it on, and it might be going on 6 months before the the crop's gonna be out there that you just really don't know.
Dan Kaiser:
You know, a lot of the things with rate I mean, I I agree with that. We have to be careful because a lot of people talk about reducing rate. Like, that's gonna be the the be all end all on this. And I think a lot of the issue when it comes down to a lot of our loss potential really is just having too much out there too early, and and timing really becomes more of a problem. I think it just gets lost with a lot of people.
Dan Kaiser:
They think just cut rate and our problems will be solved, and I don't necessarily think that's that's the case.
Jeff Vetsch:
I think you you can't have this this discussion without also thinking about kind of cultural and economic changes in agriculture over the last at least 40 years. And I think back to when I was growing up on a farm in the in southeast Minnesota in the 19 eighties and the farm crisis of the eighties and what a huge impact that had on land use and how, and cropping systems in that part of the state. And it also it also affected western Wisconsin and northeast Iowa. You just saw a lot of less small dairies. A lot of farms were sold or were lost, financially due to the economic crisis, more rented land.
Jeff Vetsch:
If you're gonna rent farmland, you're probably not gonna grow a bunch of alfalfa on it. You're probably gonna go to cut or go to row crops, corn and soybeans. And growing up in Houston County, there was not many soybeans when I was a kid. And today, you know, soybeans are just as prevalent as any other crop in southeast Minnesota. And we know row crops are gonna be leakier, and that's gonna contribute more to nitrate losses and not only to to surface waters, but to groundwaters.
Jeff Vetsch:
And that's certainly been a factor whether we you know, it's harder to quantify, but it's definitely been a factor.
Jack Wilcox:
Let's talk about technology. Dan, when we discussed MRTN a while ago, you talked about that being a starting point and then leveraging tech to get really where we need. How has technology changed or maybe not changed over the last quarter century?
Dan Kaiser:
Well, I think the big thing on technology is, I mean, you look at, like, us in the research side is it's hard to keep up with what's going on. I mean, for us to do research, it takes, you know, a good 6, 7 months to grow a crop. Where you look at the technology advancement, how quickly they can get some of this newer technology in and out of the market, it it isn't always the easiest thing to do because when we look at research, we like to have a few years of data before we look at recommending a lot of this. So that's the challenge. I think there's there's a thought out there that it'll solve a lot of our issues.
Dan Kaiser:
You know, I think there's some things we can do. And, I mean, on nitrogen, the management side is I mean, growers, they really want that option for variable rate n, and I think a lot of them think they have it. But it's you know, right now, we're dealing with nitrogen in a lot of those inputs. You know, if you look at our data, you know, what we can raise roughly 65 to 75% of our crop on the nitrogen that's mineralized from the soil yearly. That's just something that's really hard to predict.
Dan Kaiser:
This development being outpacing a lot of what we can do on the research, it's it's really hard to keep up, and it's just amazing to me. If I look back the last been here for over 15 years in Minnesota, The stuff that's come and gone and what's actually stuck in terms of particularly precision ag, how much stuff has been developed and it just kinda gone by the wayside just because of not finding a a good or consistent use for it. It's one of the things why I like the MRTN approach because it's actual real world data. It's a lot easier for me to count on, and it's just kind of up to us just to figure out how to utilize it.
Brad Carlson:
One of the things that's made a big improvement is the technology for doing fertilizer application. I think there's, been a lot more flexibility now than application. I think there's, been a lot more flexibility now than there used to be as far as particularly applying in season nitrogen, and and there's been a lot more innovation with what happens with the with the planter. The technology with respect to advising exactly how much fertilizer we need, has really been kind of a different, different side of the coin. From a a big picture perspective, when we look at these technologies, farmers become very enthusiastic if they think they're going to increase yields, but if they find out that, well, actually, their yield is probably maximized already, and the technology is more likely to be advising, reduced inputs and the the potential profit per acre is way less by cutting back on some inputs than it would be on increasing yield.
Brad Carlson:
That enthusiasm tends to wane. And so when, Dan, when you talk about a lot of the technologies that kind of came and went, in in many cases, it wasn't because they didn't work. It was just simply because, on the marketplace, they kind of failed because not enough people were using them. And so really as we move forward, a lot of those technologies that potentially will be advising how much fertilizer we put on, is probably gonna have to be more than just simply, can I save $9 an acre on a little bit less fertilizer? It's probably gonna have to be some other pressures put on as far as environmental or even closer economics, before farmers really want to start embracing that type of technology.
Dan Kaiser:
It's a question, have we gone too far with some of this stuff? It's just amazing to me. You know, you look at biologicals, I mean, you look at precision ag technologies. I mean, you know, Brad, you mentioned some of the fertilization or the the recommendation technologies. I mean, when you look at growing a crop, it's relatively simple.
Dan Kaiser:
You you stick the seed in the ground as long as there's enough nutrients there and there's water and you take care of the pests, I mean, you can grow a decent crop. Do you need some of this stuff? No. You know, when it comes down to it, I think with a lot of these increasing pressures, particularly on some of these environmental issues, that's really where a lot of these things are gonna come into play. And the the big thing I can say to I mean, really to growers is, I mean, it's you know, a lot of this technology is like getting a new toy sometimes.
Dan Kaiser:
It's kinda fun for a little while, but then, you know, looking at it again, farming, you gotta make money. So if you can't come out with any, you know, benefit of it, you know, what's really the use? And, you know, that's, I think, the thing we're seeing right now, particularly with a lot of these biologicals. I mean, the the technology's there. The stuff's interesting.
Dan Kaiser:
But I when you look at the data, I mean, the data's not there. I mean, the really the biggest caution I have for most growers since we don't see a lot of regional reporting on to go out of the ag media now, is when you start seeing things in some of the magazines and, you know, things that look interesting, you really gotta drill into this stuff more than you you really had to in the past just to make sure it's relevant. You know, I I mean, I like looking at this stuff too. It's just, you know, I kinda look at it a little bit more on the old school side in terms of of management that, I think sometimes we we think these technologies are gonna do more than they actually do and kinda lose sight of some of these these foundational principles, particularly when it comes to nutrient management to make sure that we we have things set up in place where we can we can achieve maximum yield.
Fabian Fernandez:
A lot of these technologies like remote sensing and things like that. I think they definitely have a place, but, the the challenge with some of these things is that we sometimes get kind of a false sense of security that we have all these information. But then it's like, what does that information tell you? How do you use it to to make a difference? That's that's the the big challenge.
Fabian Fernandez:
We talked about things that have come and gone. I mean, in the last since I've been here in Minnesota in the last 10, 11 years, models were a huge thing, you know, for nutrient management. And people will have kind of this dashboard of controls that show, you know, this is how much you have right now in the tank, and this is how much you're losing and all these kinds of things. But, ultimately, all of these things come back to basic principles of nutrient management and all these uncertainties that we talked about. And these models are you know, the definition of a model is a simplification of of reality, and that's what they do.
Fabian Fernandez:
While they can be helpful, a lot of times, I think that people kind of get these false sense of security that, we know exactly how much is is in the system when in the reality, we have a little control or actually know what is actually in in the in the field.
Carl Rosen:
Yeah. And just to kind of follow-up, I I don't think models are gonna go away anytime soon, especially as we collect more and more data. Big data, that's kind of the buzzword these days. And machine learning and things like that, those are just models, ways of different ways of saying models, and I think that's still going to occur. I think it's something that we'll be looking at.
Carl Rosen:
But as you say, having having real world data is to calibrate or validate those models is is what's going to be needed. One thing that has changed a lot over the last 25, 30 years is how we communicate. We did not have the Internet as as much as we have now. We have an excellent nutrient management website now that, you know, we had a lot of information, but accessing it was not that easy. Now you can access a lot of that information, all the research based information that we have on our nutrient management website. So that's been a big change, a change for the positive.
Jeff Vetsch:
Collaboration goes with that communication, and those collaboration is that collaboration has led to partnerships with all of our stakeholders, whether they're government agencies, the industry, the University of Minnesota, other land grants, our governing bodies, and that has put together and resulted in some pretty significant achievements. The MRTN database is an example, AFREC, the Fertilizer Research and Education Council, other new funding opportunities to do soil fertility research and education, and that has really may have been a big impact here, in recent years, and it's brought the commodity groups closer together to work to find solutions to agronomic, economic, and environmental concerns and issues.
Carl Rosen:
And just doing these kinds of podcasts, we would not be doing this 25 years ago.
Fabian Fernandez:
Other things I've I think have changed over the last 25 years, in terms of, Nutrien Technologies. By saying them, I'm not necessarily I'm saying that I'm endorsing them, that they work, but there are certainly things that that have kind of been developed over the last quarter of a century. Seed coatings using micronutrients mixed with macronutrients in the fertilizer. TSP is kind of one interesting one that, you know, triple super phosphate was kind of a major nitrate or phosphorus source, and then it kind of went away. It feels like it's maybe starting to come back again.
Fabian Fernandez:
So things keep evolving and changing. The other one that, we we are doing a lot of research with right now is, polymer coated urea. I mean, it started more than 25 years ago, but it really and truly from a commercial agriculture standpoint, it's something that has been kind of started around 25 years ago or so, a little bit more than that. But, inhibitors, you know, some of the inhibitors have been going for a long time. There are some new developments with nitrification inhibitors and urease inhibitors, those kinds of things.
Fabian Fernandez:
And, of course, along with all the development of trying to figure better ways to manage nutrients that are a whole bunch of snake oils and that has been a constant, in the last 25 years plus, many more years than that. And they will continue and it seems like the strategies to push these snake goals continues to be about the same as it has been, but it seemed to be effective because people keep keep falling for them.
Dan Kaiser:
You know, this was brought up before and it's one of the things that, you know, with the technology we have, especially with AI, I think there's this this thought out there from some even some of my colleagues that, you know, we don't know no longer need to do a lot of the small plot research we do. You know, in the end, you know, while we can correlate a lot of things together and have AI dig into some of the data and kinda see some general trends, we still need to have something out there essentially that gives us some assurance that what we're doing makes a difference. And that's really where a lot of our our work kind of comes into play and where, you know, it's still important to really to have people out there to really look at some of this causation of in effect studies. So there's still a reason for us to go out there and actually do the research in the field.
Jack Wilcox:
Fabian, we have 2 conferences coming up in February, don't we?
Fabian Fernandez:
The nitrogen conference is, I think, in the 11th year this year, and, it will be on February 4th in Mankato. The topics in that conference will range from talking about nutrient management and crop production, looking at last growing season and the things that we have learned from there, how we can do our own studies to to manage nutrients better, and then talk about some of the research that is going on in terms of production agriculture as well as environmental aspects of nitrogen management and and some of the, cover crops and cropping system aspects of nitrogen management. And then the nutrient management conference going to happen in Saint Cloud on February 18th. In this conference, we normally talk about all sorts of different nutrients. This year, we are actually doing something different.
Fabian Fernandez:
We are actually going to have focus on phosphorus. All of the talks will be related to phosphorus, and so I'm really looking forward to both of these events. The registration is up and running. So if you go to the, University of Minnesota Nutrient Management webpage, you can find the link to register to to both of these events.
Jack Wilcox:
You can find out a lot more about those conferences, look at agendas, and register by going to z dotumn.edu/2025 conferences. That's 2025 conferences. Thank you guys very much. Dan Kiser, Brad Carlson, Fabian Fernandez, Jeff Vetch and Carl Rosen. We appreciate it.
Carl Rosen:
Thanks, Jack.
Carl Rosen:
If you have a question or comment about something we covered today, send us an email, nutmgmt@umn.edu.
Jack Wilcox:
We'd like to thank the Agricultural Fertilizer Research and Education Council or AFREC for supporting the podcast.