Talkin' Crap

Inside the Iowa Nitrogen Initiative: Rethinking Nitrogen Rates 

Dan Andersen Episode 20

In this episode, Dan Andersen is joined by Mitch Baum to explore the Iowa Nitrogen Initiative - an effort to improve nitrogen management on farms. They delve into how on-farm nitrogen rate trials are being utilized to maximize nitrogen efficiency and introduce N-FACTS, a new tool designed to help farmers optimize nitrogen use for improved yields and environmental outcomes. 


Show Notes

N-FACT Tool



Dan Andersen:

Hello and welcome to Talkin' Crap, a podcast by Iowa State University, Extension and Outreach. This institution is an equal opportunity provider for the full non discrimination statement or accommodation inquiries, go to www.extension.iastate.edu/legal. In this podcast, we discuss insights into the science technology and best practices surrounding manure management. Our objectives are to build awareness about the challenges farmers and the broader agricultural industry face around manure and to demonstrate solutions and areas of innovation. Hello and welcome back for another episode of Talkin' Crap. I'm Dan Andersen, and today we're going to be talking about the rising optimum nitrogen rate for Midwest corn production systems. And I have a guest today, Mitch Baum. I've had the pleasure of knowing Mitch for a few years now, and he is a great nitrogen scientist here at Iowa State done some recent work, and I'm going to let him introduce a little bit more about it himself. But he's an agronomist on the Iowa nitrogen initiative team, doing a lot of the science behind that.

Mitch Baum:

Well, first off, thank you for having me, Dan, this is my first podcast, and I'm happy to do it and talk crap with you. I was actually recently promoted from postdoc to technical program specialist earlier this month, so I'm doing something right with the Iowa Nitrogen Inititative.

Dan Andersen:

All right? Yeah, congratulations. And more than something, right, you're doing a lot, right? I think the work you've done is really fundamental for helping us understand these systems, and I'm super excited to talk about it today. Can you tell us a little bit about your

Mitch Baum:

Yeah, sure. Well, first off, let me tell you what background? I do with Iowa Nitrogen Initiative. I'm kind of the data guy, so I get all of our data from on farm trials, and I fit the optimum nitrogen rate, or I determine the optimum nitrogen rate and relay that back to farmers. And then once I do that, I get to start asking the real fun questions is, why is it variable? How is it variable? And really start to investigate the management practices, the differences in soil and weather that drives those differences.

Dan Andersen:

Yeah. And I think that's been really great. And that goes to a little bit towards the paper that I wanted to bring on and talk to you today. One of the things we had used for a long time in Iowa is Maximum Return to Nitrogen, and it looked like a pretty static or constant rate for a long time.

Mitch Baum:

Yep, yep, it sure did.

Dan Andersen:

And we use basically the same number all over. And I think a lot of the work you're doing is understanding why maybe that may or may not be true, what drives it to be different on different

Mitch Baum:

soils? Yes, exactly. The MRTN was a terrific tool, and it did a very good job with the data they had and the time that it was, but now we have the capability and the technology to kind of build on top of that, to build more spatial nitrogen rate recommendations.

Dan Andersen:

And that's one of the big changes between what they were doing to come up with mrtn, and really where the Iowa nitrogen initiative has went. We had 10 farms from Iowa State involved in the trials.

Mitch Baum:

Yeah, I'd say seven to 10 every single year. It kind of varies. During my PhD, I was fortunate enough to have my hands on the data for seven of them, but I knew there was always a couple more being coming in each year.

Dan Andersen:

That floated sort of in and out. And then on the Iowa Nitrogen Initiative, every year you're doing approximately how many trials now?

Mitch Baum:

Oh, we have been growing exponentially. So in 2022 I think it was about 70,'23 it was 330, '24 330, this year, over 500 but I think we might try to slow down and settle with only, you know, a small amount of about 400 a year.

Dan Andersen:

but that's a huge difference in just the amount of data that you have to fit curves from. So when we think about spatially, how variable Iowa might be, when you have seven farms a year, it's hard to tell any one is really different than another one. And all of a sudden, when you have 300, 400 that opportunity exists.

Mitch Baum:

Oh, yeah, the amount of power we're getting with all of this data to really drive home spatial differences, it's really never been seen before in the Midwest, or maybe anywhere as far as my knowledge, for making nitrogen recommendations. It's really cool.

Dan Andersen:

Yeah, okay, so I wanted to talk you guys do a lot of, I'm going to say, remote sensing, but especially soil tests on your sites to help understand fundamentally, why a site might be different than a different farm. So why your field might be different than my field? Could you walk us through just a little bit of what you're looking for and maybe what some of the most important things you measure are?

Mitch Baum:

So, we really want to look at different management practices, different weather. So we ask all sorts of questions, maybe even too much, but we want to know like the planting date, the plant population, the previous crop, the cultivar, if possible. In terms of soil, we're really interested in organic matter, the amount of residual nitrogen, spring nitrogen, and things of that nature. And then, you know, we get weather information from outside sources. Primarily the Iowa Mesonet.

Dan Andersen:

Perfect. So when we think about this, every site, you're getting a fair amount of soils data, some more than others, and then you're overlaying on that site sort of a field trial of different nitrogen application rates. And it's mostly focused on that when you actually lay it out at nitrogen application rate. But you might have 20 sites in a in a county or in a region with various management practices where I know till you strip till so you fundamentally have an opportunity to get and ask the questions of, do those things seem to make a difference?

Mitch Baum:

Yep, and that's really one of the beauties of the study, is it's really designed to integrate well into what a farmer is already doing. We really want to. Our big thing is varying N rates. And right now, we don't say what these nitrogen rates are. It's really what a farmer is comfortable with. If they're willing to go to zero, that is amazing. And we'll pay you a little bit of money if you're doing that. If not, that's okay too. We'll still fit the optimum nitrogen rates. And, you know, do the best we can. But everything else, whether it's planting date, fungicides, tillage, crop rotation, it's really what the farmer was already doing. Our process is very seamless. The agronomists from Premier Cropping Systems will work with the farmers to implement these trial designs into their equipment, their applicators, and then it's as easy as the farmers just driving through the field, and then at the end of the year, driving the combine through the field, and we'll give them their results.

Dan Andersen:

And that's actually a little bit different than the setup we had with the Iowa nitrogen trials that were used in MRTN, where it was really prescribed of this is a no till system. This is a tillage system with either continuous corn or corn, corn soybeans. You've moved to a model where farm like you farm. We want to know what optimum and would be on your farm, and you're just collecting data from enough sites to sort of what does that mean, and how do I interpret it, rather than having to prescribe everything?

Mitch Baum:

Yep, exactly. And this is really building a very unique, very diverse data set that has really never been seen before. The long term trials behind the MRTN were based around two crop rotations, and, you know, several sites a year, but all else really held constant. Planting date was the same within a single site, tillage was the same within a single site, pesticide, fungicide, all that the same. And then, you know, it varied across sites, mainly with planting date, you know.

Dan Andersen:

Yeah, whatever was right for that region. Northern Iowa might be a little different than southern Iowa, but you're getting this climatic gradient, not really a management difference that was driving it, right?

Mitch Baum:

Exactly.

Dan Andersen:

And I think that's one of the things that really makes everything you're doing neat. There's a lot of data behind it where we can start to tease out, or you can start to tease out some of those interactions. What happens if I end up planting two weeks later than my neighbor because I have lots of acres to get through before I got that field planted?

Mitch Baum:

No, I completely agree. It's very exciting, and it keeps me a job. So I just really look forward to looking into all of that.

Dan Andersen:

Yeah, we've done nitrogen management for a while. We have a lot of we know a lot, but there's still so much more to go. All right, I wanted to transition a little bit, and one of the things you did maybe a year and a half ago was you came up with a paper on nitrogen use efficiency of corn, or partial

Mitch Baum:

these nitrogen decisions. factor productivity, depending on how we want to call it. But it's really, I mean, I'm a manure guy. Lots of people who listen to this think about yield goal method yet, and in some ways that nitrogen use efficiency income informs yield goal, because yield goal is based on how many pounds of nitrogen does it take per bushel of corn. When we think of that publication, what did you learn from that? And what do you think

Dan Andersen:

Perfect. And I think that really takes me to the paper. You put out great paper, and one of the things that was really unique about it is you tracked nitrogen optimum nitrogen rates as a function of time on these plots, and that wasn't really something that scientists had done before. So how did we analyze the data before? What was the recommendation and what inspired you to start thinking about is there a trend with time?

Mitch Baum:

Well, let's start with the previous recommendation. So the thought behind the previous recommendations was they would just average a bunch of trials together, and you know, you wouldn't capture the spatial or temporal variability, but on average, you're going to do a lot better than just guessing. And many papers have shown or reiterated, yeah, that's really good when you're looking at long term averages, it does fine, but when you start diving into year to year, it kind of, you know, it's not as good. And there to combat this, many new systems been developed, whether you've already mentioned remote sensing or crop modeling, which is where I really came in. I was given all of that data actually, not to look at annual trends of optimal nitrogen rates, but to try to calibrate a crop model to see if we can enhance, you know, on the current method. Well, you know, you're a manure guy, so you've probably heard this before. You put crap in, you get crap out.

Dan Andersen:

Absolutely.

Mitch Baum:

And models are no different. So before I even started modeling, I dove into the data set to see, you know what was happening. And at the time, I had just started my PhD, so I really didn't appreciate the finding. I think I was just actually going home and I was walking past my advisor's office, I was like, Oh, hey, have a nice night. By the way, the optimum nitrogen rates are increasing. That's kind of cool, huh? He's like, and then, you know, after that, he called me into his office next day, and we had a long discussion about it. But yeah, it really was a surprise, because the general consensus before that, and really a challenge throughout my entire PhD was trying to combat this paradigm that there is no relationship with the optimum nitrogen rate in time. But lo and behold, I took this data set, analyzed it a little differently, and the trends were kind of clear.

Dan Andersen:

And part of it was just you started looking at all the sites together and really focusing on separating by year. And I think one thing that before and this sort of comes out with what you're doing with the Iowa Nitrogen Initiative, when you have a limited number of trials, it's hard to pick up trends. You start saying, Well, I'm just going to group everything together, but you got some data from both Iowa and Illinois for your paper, I think. And by maybe focusing on changes with time, you really did have that pop out to you?

Mitch Baum:

Yes, yep.

Dan Andersen:

Okay, so one of the things you found was that the nitrogen rate for corn following soybean is increasing faster than corn following corn. What's up with that?

Mitch Baum:

That is a great question, and I don't 100% know, but we pretty confident it's because the yields for the corn soybean rotation are increasing faster than the yields for continuous corn. And this could be due for several reasons. One could be that all the breeding programs right now are developed using corn soybean rotation, so maybe we're inadvertently selecting for that system compared to corn-corn. Another one is potential diseases, right? Which can really shave off the top end yield for the corn-corn system, whether it's allopathy from the roots or, you know, tar spot over wintering on that residue.

Dan Andersen:

Yeah, so that's an interesting one. Though, I think we've recognized for a while that there might be a continuous corn penalty for lots of reasons, but I had no idea that yields were actually probably increasing faster in corn soy than continuous corn. So that is an interesting finding. And yet, despite that, on a lot of farms, I work with, manure inspires us to be continuous corn for various reasons, right? I don't want to haul my manure as far, and that's one way to keep it a little closer to the barn.

Mitch Baum:

I mean, I don't want to shoot down continuous corn. The yields are still increasing.

Dan Andersen:

Yeah, just not maybe quite as fast. But there's also maybe some management strategies with continuous corn to alleviate some of that yield penalty, penalty. Do you think farmers might have found a way to farm through it better than if I just go, I'm going to be a no till, no matter what.

Mitch Baum:

Well, I think you're more of the expert on this than me, but yeah, the more you can try to replicate the corn soy system and that, you know, the main difference is residue, right? Soybeans don't produce nearly as much residue as corn. If you rationally remove some of that residue or till it in, you will stimulate early season mineralization, maybe drying up the soil faster, potentially plant earlier. All things that can improve yields in the continuous corn system.

Dan Andersen:

That was interesting, and I never thought about it quite that way. But one thing that we might say from that is, if I was a dairy farm making corn silage, maybe continuous corn doesn't have that negative I've already started removing some of that residue, and I've made it look a little bit more like that corn soybean system. So another reason that, other than just how far I have to move my manure, that we might be inspired to try more continuous corn in some of our livestock farms. Okay, so we found the nitrogen need is rising. Let's talk a little bit about what does that mean for sustainability? Are we getting better. Is nitrogen use efficiency improving too? How do all those factors sort of tie together? to make that come true.

Mitch Baum:

Yeah, great question, Dan. We did find nitrogen use efficiency was increasing over time, and that's a really interesting finding, that both the optimum nitrogen rate or nitrogen demand is improving as we're getting better, more efficient with our nitrogen applied. And if we weren't getting better with the nitrogen applied, the amount of increase for the optimal N rate would be even higher. And the main reason for this is is because of the high end yields, the genetics and management practices and maybe even environment nowadays are promoting higher yields than ever before. But what we found also was the yield at the lower nitrogen rates, the yields primarily driven by the amount of mineralization, or the amount of nitrogen supplied by the soil, was really non changing over time. So what you have is this divergence of increased yield potential realizing it, but the amount of nitrogen from the soil either remaining the same or not increasing at that same rate. So nitrogen use efficiency wound up increasing along with the optimal nitrogen rate the demand, the increase in demand was just so great that it kind of counteracted it.

Dan Andersen:

That's interesting. But fundamentally, it's not just genetics. Because my your zero yield, your zero nitrogen plots, which are hard to get, but they did in the maximum return to nitrogen trials, you don't really see a trend of increasing yield with those. They're moderately steady, high variability, I assume because of mineralization from year to year,

Mitch Baum:

Of course, yeah.

Dan Andersen:

But you still see that the optimum yield, if I'm hitting the fertilizer levels I should really, is increasing, and we see a pretty strong trend of that every year in the crop reports that we get out that yields increasing. But it's not fundamentally just doing that at zero nitrogen. It takes some

Mitch Baum:

Yep, absolutely. And I also want to point out that the yield at the optimum nitrogen rate was increasing at the same rate as the yields for the county, as reported by USDA NASS. So what our improvements in yield are very reflective of what was seen. You know, across the state.

Dan Andersen:

We worry about farmers hitting that nitrogen fertilizer recommendation, and I think that's data that maybe suggests, in general, they're doing a halfway decent job. Farms are very variable, and we don't have that all figured out yet, but when you see the optimum yield increase trending roughly similar to what it should be on these trials, that seems like a good sign that they're at least staying in pace with where we need to be exactly.

Mitch Baum:

Yep.

Dan Andersen:

Awesome. All right. So as you think about tools we have today, mrtn was out there. I was not really using that recommendation system anymore, though we went to something a little new. Could you talk us through that just a little bit ?

Mitch Baum:

Yes, back in February, a product of Iowa Nitrogen Initiative was the new N-FACT decision support system. And this is really two tools wrapped into one. The first tool is all about reporting the results of the INI spread across differing management practices. Right now it's crop rotation, continuous corn or corn following soybeans and regions. So we have eight major land resource areas defined by, you know, different soils, the Des Moines lobe being a predominant one. And what farmers can do is they can look at all of the information we've obtained from the real on farm trials of the Iowa Nitrogen Initiative, and compare what they're doing versus what has been seen, and they can really benchmark it themselves, so they can see the optimum nitrogen rate for, let's say Boone County, for a corn soybean system, was 180 pounds on average. But it ranged from 130 all the way to 240 depending on the different system. And they can look at that and think, Well, I'm applying 275, you know, maybe I could come back down a little bit, or vice versa. They're like, Oh, I'm only applying 140 maybe, maybe I can bump that up a little bit.

Dan Andersen:

That's right, and see some yield increases with that. So it gives you some idea of maybe where your neighbors are, where the optimums are in sort of that region in that year. And now you've been doing this for three, four years now, which is a while, but also in the grand scheme of weather conditions that we encounter not the most variable things that we might see, although you started in some dry, dry years, and now you're getting some wet years, which is probably nice from a perspective of how different are they.

Mitch Baum:

From a science perspective, we love it, right?

Dan Andersen:

Yeah, I think from a growing corn perspective, I could have used a little less water this year, but yeah. So when you think about that data is, has there been a big difference in maybe some of those dry years compared to wet years? What have you seen?

Mitch Baum:

We've seen so right now we're really playing with two years, 2023, and 2024 2022, was great, but it was really kind of a trial year for us, we have the bulk of our data from'23 and '24 which of course, '23 was a lot drier than '24 and what we found was the optimum nitrogen rate increased when it was wetter. The yields increased when it was wetter. However, the pounds N per bushel also increased, which is not necessarily a good thing, even though it's an increase, but that was primarily due to increasing optimum nitrogen rates, more so than increasing yields.

Dan Andersen:

Yeah, and I think weather's tough, and I think that's something we've heard for a while. You don't get to control the weather. If we could, we'd dial in the perfect growing conditions every year, but definitely understanding maybe a wet year, I need to make a different fertilization decision for rate or how I'm going to get it out there to be less sensitive to timing might be useful, but understanding sort of what drives that variability extremely important. And I won't push you on 2025 because we could sit here and say, Well, you've seen '23 you've seen '24, what does '25 look like? And that's really the game we're going to ask farmers to play, but we haven't seen a year like '25 so it's hard to look at the database and say, I think it's going to be there, right? But I mean that is ultimately where you're trying to get through with a rate prediction tool.

Mitch Baum:

Yep, and I think that plays greatly into the second part of the N-FACT tool. And this one allows farmers, or really, anybody, it's free for everyone to select a county, select a region, your soil type, your crop rotation, your planting date, residual nitrogen. But also a factor you can play with is dry, wet or average spring and summer weather. And when you select all of those, you can really play with or see how changing a dry spring versus a wet spring impacts your optimum nitrogen rate. And you know, vice versa for a dry summer versus average summer. And what it allows farmers to do is really start thinking about, Well, this year was drier. What would it have been like if it was wet? You know, I really think, I know the spring was dry, but I think summer might be wet, you know, kind of like this year. And you can play with that to see how that changes, the optimal, the range of optimum nitrogen rates relative to, you know, your known planting date, soil conditions and county.

Dan Andersen:

Yeah, and I think that's actually extremely powerful. One of the things that you got me thinking about. You came over one day and gave a speech at an extension in service we were holding, and you sort of showed us that it wasn't so much just timing was changing what was happening with fertilizer, but by being a little further in the growing season, you knew a little bit more. You can make a better estimate of, I think optimum end rate is going to be here, and that change in optimum N rate at least as important as application time, and probably more so from the data that I've seen from you. I think that was extremely powerful, and we want more data, but we need something to understand how to make decisions with it, and that finally gives us a mechanism to do that. If I've been having that wet spring, well, I know I've had potential for a little bit more loss of nitrogen. How does that impact what I really need this year? And can I go and put a little more on so I think that is an extremely handy tool, especially when we look at maybe the on farm trials, and say, I haven't had a year like '25 yet. What does that mean for what I actually did this year? And if you go, click, well, I didn't know it was going to be a super wet spring and a wet early summer, but all of a sudden we have that possibility to say, well, it looks like, on average, we needed 30 pounds more than last year, or whatever. You can adjust accordingly.

Mitch Baum:

Yes, you can. And that's really the real power of this tool also, is that it doesn't only just give you one rate, right? It gives you a range of optimum nitrogen rates to play with.

Dan Andersen:

Yeah, and I think that's one thing. It's always hard to understand what the variability is from my farm to your farm. And this tool sort of helps us recognize that right like different management strategies might impact our optimum nitrogen rate for various reasons. And you give us a lot of tools to sort of say, maybe it was planting date, maybe it was rotation, some of its soils within a county, how much nitrogen carryover is left, but and then the weather conditions. What else are you guys trying to get in there? What other factors do you feel like, what's the next big one you want to get in the model to sort of say, I want to select this?

Mitch Baum:

Well, I can't say what's going to actually go in or not at this time, I know we are looking at things like organic matter. We are looking at residue removal, potentially the timing of when those go into N-FACT, I can't say at this moment, but I will say, the more information we have, and I should say, the more information we're really confident in. There's a good chance it'll make it into N-FACT.

Dan Andersen:

So some of it is having farmers that try some of these different practices, so that you have on farm trials that sort of back up what the model's saying and what you're seeing.

Mitch Baum:

Yep, yep. We will not put anything in there that we cannot we're not scientifically confident in.

Dan Andersen:

So if you're out there doing some residue removal, and you're like, I want to see how that changes me compared to other people N-FACTS would be definitely interested in that sort of site. So if you're a cattle guy out there making stock bedding to get out of the way of your cattle, probably good chance to say that's a plot we might want to look at and hopefully get involved in this trial to say, Does residue removal make a difference?

Mitch Baum:

Yeah, yep. And I think we're heading that way.

Dan Andersen:

Beautiful. All right, so there is a lot of information that you've collected, a lot available to farmers to use consultants to use what do you think the first step they should do, especially for manure guys who have been using maybe that yield goal method. And think about it a lot, and I'm maybe not quite ready to jump and say, I'm using n facts tomorrow. How should I use the tool? How should I be thinking about it and maybe getting ready to transition?

Mitch Baum:

Well, I would just like to reinforce that, to really think about your cropping system and the key drivers of what may be impacting the nitrogen management on your cropping system. And you can use tools like N-FACT, to help see how far changing those factors will shift your optimum management, but the just the general mindset of that this is very variable. This is changing field in, field out, operation by operation, and you now have tools to look at to help you make the best decision possible.

Dan Andersen:

Perfect. So it's not that yield goal is wrong, but it sort of gives you this one size fits all. I have this algorithm I just apply, and that's the rate I'm going to use, whereas N-FACT says maybe you can do better than that. And I think the data from the publication on nitrogen use efficiency says, on average, the state's probably a little better than what a yield goal method would suggest, but understanding what's driving that so that you can replicate it on your farm and say, maybe I'm already one of the farms that's better than that. I don't need that full yield goal method. Or maybe I'm worse than that, and I do are really important to making sure we're maximizing production while protecting environment.

Mitch Baum:

Exactly. And you know, you and I authored a publication about the pounds N per bushel and how that might change across time, and really not cross, I'm sorry, across counties. But really try to consider, you know, your pounds N per bushel when making a yield goal recommendation, and think about, you know, is it you know, where it should be? Is is it above 1.2? Hopefully not. Our data shows it's much closer to point nine, yeah, or point the upper point eight, that's right, and 1.2.

Dan Andersen:

And even with the 1.2 number I've played with those on farm trials, like if you're above 1.2 that happens 5% of the time. Almost everyone in those trials is well below it, and we think about using the yield goal method. It's not the worst method ever, but it's probably on the high side. We can probably dial those nitrogen rates back on most Iowa systems.

Mitch Baum:

Yep, I agree. And most, more often than not, from what I've seen, when you have a pounds N per bushel greater than 1.2 it's because something really chopped off the high end yields, right for whatever reason, your yields just weren't where they should be. And I

Dan Andersen:

And I have an example of a place that might it definitely back. Thanks so much. Mitch. sometime. won't be that way this year, but I'd feel that way. I went to Ag 450, got some manure. Have done this for a few years now, and it always tests 60-65, pounds of nitrogen per bushel or per 1000 gallons, and this year it was half that. So I'm looking at my cornfield and say it's really bad. It's really bad. I didn't send a pre sample. I only sent that post sample. That post sample, and I knew I was off. But if I did, wasn't, hadn't sent that sample, I would have said, Man, I needed a lot of nitrogen this year. No, I needed probably about what I normally need. I just put on half of what I thought I was actually trying to put on. In that case, I know it was bad, and it taught me a lesson, right? Don't rely on that past history of samples to sort of inform what I'm going to do, especially when it's a barn I don't manage and don't know that something different happened this year. They had a had a water leak and diluted some manure for me. But it happens, all right, so I wanted to say thanks for Mitch for joining us. I think that was a great discussion of, sort of where the Iowa nitrogen Initiative is a lot of the power behind those on farm trials to see how you're comparing to your neighbors what's possible in your area, and then starting to think about what causes and drives that nitrogen need for different crops based on the management decisions we're making. So I appreciate all the work you're doing. I appreciate coming in to take a chance to talk to us and really talk through maybe why we've seen that nitrogen need is increasing while we're still improving performance in terms of pounds of nitrogen per bushel we need.

Mitch Baum:

Yeah, well, happy to here. Hopefully I can Yep, thank you.

Dan Andersen:

Thank you for joining this installment of Talkin' Crap. Be sure to take a look at the show notes on our website for links and materials mentioned in the episode. For more information or to get in touch, go to our website, www.extension.iastate.edu/immag/. If you found what you heard today useful or it made you think, we hope you subscribe to the show on your podcast app of choice, signing off from a job that sometimes smells but never stinks, keep on talking crap.