UMN Extension Nutrient Management Podcast

University of Minnesota Nutrient Management Podcast Episode: “Nitrogen management and water quality in Southeast Minnesota”
December 2023
Written transcripts are generated using a combination of speech recognition software and human transcribers, and may contain errors. Please check the corresponding audio before referencing content in print.

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Jack Wilcox:
Welcome back to the University of Minnesota Extensions Nutrient Management podcast. I'm your host, Jack Wilcox communications generalist here at U of M extension. In this episode, we're talking about nitrogen management and water quality in Southeast Minnesota. We have three panelists here with us today. Can you each give us a quick introduction?

Brad Carlson:
Yeah. Brad Carlson. I'm an extension educator. I work out of our regional office in Mankato, focusing a lot on issues related to nitrogen management and nitrates in water. And I work statewide, so obviously that includes the Southeast.

Jeff Vetsch:
Hi, this is Jeff Vetch. I'm a researcher and soil fertility person here at the Southern Research and Outreach Center in Waseca. And yeah, as similar to Brad, I spend a lot of time working on nitrogen management, nitrogen best management practices.

Greg Klinger:
I'm Greg Klinger, I work for Olmsted County Soil and Water Conservation District, and I oversee a state program called the Minnesota Agricultural Water Quality Certification Program for Southeastern Minnesota.

Jack Wilcox:
All right, let's jump right in. What's the situation in Southeast Minnesota and why is it different from the rest of the state?

Greg Klinger:
Yeah, Jack, that's a great question. So there's been a lot of concern about high levels of nitrate in drinking water aquifers in Southeast Minnesota. We have kind of unique geology in Southeast Minnesota that makes it easier for nitrates that are essentially accumulating in topsoil to make it into especially shallow groundwater aquifers. We have what they call karst geology, which is porous limestone bedrock, and it's in different layers under the ground. A lot of areas are pretty shallow soils, so water infiltrates pretty readily. And will hit that first bedrock layer, which tends to have a lot of pores in it, ranging from small cracks to very large, I mean foot wide, more than foot wide pores that will rapidly transmit water into that bedrock. And then what you often find happening is that water kind of works its way down through that layer of bedrock.

At certain points it'll hit layers that kind of slow down the water and keep it from moving deeper. And so one of the things that's kind of unique about our geology is that it is the water at different layers and the bedrock is very kind of segregated by age. In other words, in the upper bedrock layers, that water that's in there that if you have a well that you're drawing out may have fallen as rain in the last 5, 10, 20 years. But then you have lower layers where most of the water that is in those bedrock layers might be 40 or 50 years old or even older.

And of course, that's kind of an average, even in deeper layers, there might be some proportion of the water that got there pretty rapidly, but mostly it's pretty old. And so that creates some challenges because for one thing, our bedrock aquifers don't really remove nitrate very effectively. Some geology might be more effective at doing that, where over time as nitrates or water with nitrate and is kind of sitting there or moving through that layer, some of that nitrate might be removed. But that doesn't seem to happen too much in our geology. So it just makes it a little more prone to any nitrates that enter groundwater staying there.

Jeff Vetsch:
So one of the things that have brought this to the table here again recently is we know that consuming nitrate in drinking water is not good for you. And it's especially been known for many, many years about blue baby syndrome or nitrate for small children or infants that was consumed maybe from a formula mixed with water that contained nitrate can result in this medical condition. But more recently, there's becoming more growing health concerns are associated with adults that are consuming nitrate or nitrite. And there's more and more information in the literature looking at different medical conditions from increased heart rate to nausea to headaches, abdominal cramps and potential cancers including gastric cancer. And the scientific consensus on this is not completely set, but there is a lot more concern about this in recent years, and that's bringing this to the table and making it a issue and a greater concern.

Brad Carlson:
I think a lot of people are aware that there was a petition filed with the US EPA kind of asking the state to do more in Southeast Minnesota. We're not going to get into that because this isn't a political podcast. However, at this point that happened fairly recently. And the state is being directed to develop a plan. And so that's kind of one of the reasons why there's been a lot of attention called to this in the very recent past here just in the last few weeks. And so I think it's worthwhile having a conversation about what the situation actually is in the Southeast.

Jack Wilcox:
Okay. What is the history of this work in Southeast Minnesota on nitrogen issues?

Jeff Vetsch:
Yeah, so going back to the think mid, late 1980s, a lot of applied agricultural research looking at nitrogen management in this region, this research was developed the best management practice that were developed for that area. Gals Randall led extensive research in Winona, Olmsted, Goodhue counties and in other areas in Southeast Minnesota. This research generally focused on just simple production and water quality concerns and issues in that area. It was looking at the four Rs kind of nitrogen management for Southeast Minnesota, the right rates, the right timings was fall application justified or a good practice compared to spring application and recognize that this was in the 1980s and early 1990s. Also looking at sources of nitrogen, anhydrous ammonia versus urea, UAN, different times of application as I mentioned earlier. And it also looked at manure management as well. The things that we looked at in that research was corn production, nitrogen use sufficiency, and specifically from a water quality standpoint, the fate of nitrogen was monitored using not only suction samplers, but also deep soil sampling both in the spring and the fall.

And with that, we developed the nitrogen BMPs for that region and they were released in 1994. And since then, we've also probably had more than 40 N rate trials done in that area. And I would say the majority of those trials from the last 25 years are currently included in our current end rate calculator. And dozens of other NMI trials on-farm rate comparison studies have been conducted, been lots of educational and outreach efforts, many field days, education events, extension publications and fact sheets both from the Department of Ag and from the University of Minnesota. So pretty extensive research and education efforts on nitrogen management for crops in that area over the last probably 40 years, but certainly starting to really ramp up in the eighties and early nineties.

Greg Klinger:
More recently, one project I did when I was working at the University of Minnesota, so it's been a couple of years now, was going out and taking kind of across my part of the karst region, taking regular samples of tile water samples and testing them for nitrates for local farmers who were kind of interested in seeing in where their nitrate levels were. In some cases. I was doing this for up to six years, kind of depended on the farm and it was about, I think about 25, 28 different farms that I was testing nitrates on mostly corn, soybean rotation. But there were some interesting things that came out of that. And I will say it was observational. It was not the sort of thing where I could look and say, because you did this practice nitrate losses by this amount. But there were still some things that I think came out of that that were of interest.

And so one of the takeaways that I had off of that that I found really interesting was the nitrate levels actually were in general lower in that study than you would expect to see based on a lot of other researchers. There's a great deal of research on nitrate levels related to cropping systems that comes from university research. Purdue University has a really great interpretation of tile nitrate data. Discovery Farms also has a really great source of information, I think particularly in the karst region, both Discovery Farms, Minnesota and Wisconsin has a lot of really good data specific to this area. And then Minnesota Pollution Control Agency has done some work and also the Iowa Soybean Association looking at what would be typical tile nitrate concentrations for corn, soybean rotations, other rotations. And in general, I'd say that would averaged out at like 15 to 20 milligrams per liter.

Iowa Soybean Association work was a little lower, probably about 12, 13. But what's interesting was that the fields I was sampling were quite a bit lower than that about averaged about seven and a half. Again, this is observational, so I can't really say for sure why. But based on other research and just kind of what we understand about how water moves in the ground and nitrogen practices, I think there were some reasonable interpretations of why it was so low.

One was a lot of the farms that I was working with, there was a great deal of cover crop usage on some of these farms. And in particular, there's some very, I would say very aggressive use of cover crops where they're letting them grow pretty extensive amounts of biomass before they're terminating. And then the other thing which when we're interpreting water quality trends, we often forget about or don't think about quite as much, is just what were the climate conditions during the time that you're talking about, because that does dictate a lot of these trends in water quality. And I was mostly out sampling, I said up to six years, but mostly during a pretty wet period of time from 2016 to 2022. And what you tend to see is that nitrate concentrations will go down in tile water during that sort of time.

I think the understanding of why that is if you have a tile system, well, when it's really wet, the water table rises, more water gets into the tile system from below, and water tends to be from shallow groundwater, tends to be a little more dilute in nitrate concentration. So during wet periods you tend to have a little lower nitrates during dry periods a little higher. So that was kind of interesting, I think part of the interpretation. But the other thing I found really, really interesting was, so I was working with a lot of farmers doing a lot of things like aggressive cover crops. Well, one of the things that was interesting was that in the spring of 19, 2019, which was very, very wet, most of the farms I was sampling had a really big spike in nitrate levels. And if you go back and think during that period, the fall of 2018 was super, super wet, really delayed harvest.

And then the spring of 2019 was also super, super wet. And what I think was happening, again, I'm speculating, but was that so the amount of time it takes for water to move through a tile system might be on order of a year under normal circumstances. But if you have a ton of water pushing through the soil, all of a sudden that's shortened. And so where you might have a spike of fertilizer like associated nitrate in a normal year, you might have a little bit of nitrate, a rise associated with fertilizer application. Well, all of a sudden in a really wet year, like a really, really wet year, you have this big spike that you normally wouldn't have. And so that happened in 2019. But I thought it was also interesting because one of the few sites that didn't see a big spike in 2019 was a location where they had planted sweet corn, they got harvested, it was late sweet corn, got harvested maybe early September, and then they put in a cover crop.

And in contrast to most of the grain cropping fields where harvest was delayed, people who normally would've planted cover crops either couldn't or couldn't get a good stand because it was November by the time they're out there. This field really took off. And so that in the spring when you had this big push of water, there was a really healthy cover there that had probably taken down the concentration of nitrates in that water quite a bit. And so it just didn't see that spike.

And to me that was really, it made me think about just the value of some of these, especially these short season crops. Like I have a coworker who grows food grade oats or peas or sweet corn, even corn silage where you can get a cover crop or a double crop into that system and the likelihood of it failing is much less than in a grain cropping system. And so even in a year that is really hard to get that system to work for a corn soybean kind of field corn rotation, well, you might have much better success at mitigating some of that nitrate loss in those kind of short to season crop systems.

Brad Carlson:
I think if we're going to talk about history, one of the other major things that needs to be discussed is changes in cropping patterns. It's been well talked about that Southeast Minnesota is now primarily corn and soybean country, not placing the blame on that. However, we do know research shows that perennial crops do pretty much do not leach nitrate for a number of reasons. They're deep-rooted and they're continue to grow times of the year when our annual crops are not growing. So specifically we're talking about alfalfa and nitrate loss from alfalfa fields is almost zero. And alfalfa, of course is closely associated with the dairy industry. And we know that there's been a precipitous loss of small dairies really everywhere. It's not unique to Southeast Minnesota in a lot of cases, and this is based on my personal experience working in extension in a county office for many years in Rice County, which is on the border of Southeast Minnesota.

When I started there in 1994, there were over 200 dairy farms in that county. And I believe that number now is somewhere south of 60 or something like that now. In a lot of cases, what you discover when you talk to those farmers, it's really not an issue of finances. It's an issue of lifestyle that small dairy farms, the work is hard, the days are long. There's really not a labor pool out there anymore. There used to be big families, there were neighbors, there were neighboring kids who you could hire, and these guys are getting stuck doing all their work seven days a week all year round without being able to take vacations and so forth. And so a lot of the cases, the exodus of small dairy farms has been personal choice, not because they're not making money or it doesn't work. And so it's not a simple solution to just say, well, we're going to do this, and all of a sudden we're going to have all these 60 cow dairies all over the place again that are growing alfalfa.

That's probably a permanent change. And then the other issue here is that we do have a lot of larger scale dairy farms, and in a lot of cases these folks are buying alfalfa kind of on the open market because of the climate in Southeast Minnesota. In a lot of ways it would make sense for them to make their own hay locally, but it rains too much. And so it's very difficult to ensure that you've got a feed supply. And so one of the ways they do that is to simply not bother. They just import it from out west to where you can reliably just purchase forage inputs as a commodity. You see it on I-90 the trucks with the big square bales coming in. And so that has also had some impact on what's happened with nitrate levels in Southeast Minnesota is the loss of that perennial crop. And there's not an easy solution to put it back into the crop rotation.

Jack Wilcox:
What's being done about the situation and what are our current recommendations for Southeast Minnesota?

Greg Klinger:
As I mentioned, I oversee the Minnesota Ag Water Quality Certification program for Southeast Minnesota, which is a voluntary program that a farmer could choose to sign up for where we would sit down, we'd meet, we look over farm records, we talk about their farming practices, walk over fields, things like that. And the goal of that program is to get an assessment of the relative risk to water quality of that farm operation. It focuses mostly on the risks to surface water associated with nutrients and sediment as well as risks to groundwater from nutrients like nitrate and to a lesser extent focuses on risks from pesticides. And the bottom line is that in going through that assessment process, if all the fields in a farm operation hit a certain threshold, they have an overall water quality risk that's fairly low, they can be ag water quality certified, and that certification itself, it does provide some benefits.

I would say that from talking with farmers, probably the most important one for most people is just this like, look, here's an independent third party who's looking over my farm and verifying that yes, what I'm doing for conservation are things I should be proud of. There's some other kind of tangible benefits certified producers can get scholarships through. There's a great farm business management program that's kind of run through the state community and technical colleges. They can get cost share money to add conservation practices to their farms.

And then another one that's fairly new, that's a really nice advantage is they get kind of a leg up in getting grants through the states soil health equipment grant, which will pay for up to 50% or $50,000 of new to an operation equipment or modifications to equipment that'll further soil health. So things like this would be great for getting a new or used no-till planter, something to seed cover crops, things like that. I think this is a really, really nice advantage. And then the other thing that a farmer's getting going through this program is really just a different set of eyes on their operation. And I think that is a really important thing.

Everyone involved in the program and running it has different expertise, different experiences that they're coming with. But I can say from my personal experience, and I haven't been doing this super long, but every time I've gone through a certification with someone, with maybe a couple exceptions, there is something that comes out of that that is of direct benefit to that farmer in terms of their bottom line above and beyond the certification itself, whether logistically some sort of change that they might be able to do or that I might recommend them thinking about whether they can do it, that's another question whether it fits with their operation. But there is always value in having another set of eyes on an operation. And one last thing, going back to there being a lot of attention on the nitrate issue in Southeast Minnesota at the moment, the Ag Water Quality Certification program, it's voluntary.

Your farm data records are your own, they're not shared with anyone. There is nothing that says you have to get certified if you apply for the program. A way that someone could look at this is just a conversation with someone sitting down, having a conversation with someone whose background is on the water quality impacts of farm practices, and just taking a look at how do my farming practices, what is the relative risk to nitrate reaching the groundwater? And that is definitely a conversation that could be had if nothing else. I think that might give someone a little peace of mind.

Jeff Vetsch:
Another thing that's come into play in this region in recent years is the groundwater protection rule, which went into effect in June of 2019, and it limits the amount of fertilizer nitrogen that could be applied in the fall. And in general, the best management practices that were developed through the eighties and the nineties showed that fall application of nitrogen in this region was not a good practice. And that was in the BMPs and written, and I don't think there were a lot of farmers or retailers that were applying nitrogen in the fall prior to the groundwater protection rule going into effect, but it put a little bit more teeth into that enforcement.

Other work that's being done in the area, I'm working with the Department of Ag, some local farmers and their ag advisors and their ag retailers on a targeted program where we're looking at doing on-farm nitrogen rate and timing research to help identify and help encourage growers and their ag retailers that make the decisions on nitrogen rates and application and nitrogen management in that region to work with them on on-farm work to help them better identify and feel confident in the BMPs that we have in that area and hopefully see more and greater adoption as Greg said, that is purely voluntary to use those best management practices.

We are targeting this work in areas where drinking water supply management areas or DWSMAs that have elevated nitrate and have been shown from recent testing that was done by the Department of Ag. So we're targeting this work in those areas and working with some growers and some of their retailers with the hope that that helps build confidence in the best management practices and that those individuals can be spokespeople for their region and help moving on and seeing greater adoption throughout that region.

Brad Carlson:
Greg was mentioning the studies he was doing monitoring field tile, which is actually not a historically significant practice in Southeast Minnesota. It's become more prevalent, particularly as it's gotten so wet in the last 15 or 20 years. However, we do have a fair amount of research at Waseca, different soil types, but still is insightful on how the system is behaving with respect to nitrogen inputs and fertilizer inputs. And I know there's been a lot of finger pointing related to commercial fertilizer and manure use as far as being solely responsible for the problem. And the fact of the matter is that our research shows that roughly about two thirds of the nitrogen is still leaving the system even when you don't fertilize. And so soybean fields, if you do a nitrogen rate study with corn and you apply zero nitrogen, what we're still finding is average losses of about 15 pounds per acre.

And this is some of what I referred to previously when I was talking about how losing perennial crops in the landscape was a big part of the issue here. So when we talk about developing a comprehensive solution, it's going to be extraordinarily difficult because just simply, let's just say we said, oh, we're not going to apply any commercial fertilizer anymore. That's not going to solve the problem. The issue really is we got water movement going on in the fall and in the spring when there's no live plant growing out there, it's going to be complicated as far as reintroducing perennials and particularly ones that have some kind of economic value because frankly, I'm not sure if anybody's out there wanting to advocate just simply putting farms out of business and growing a worthless crop would have that effect. And the other part is trying to advance the science of cover crops to see if we can get something growing out there post growing season of our commercial crops.

But it's easier said than done. And so this is kind of a work in progress when it comes to that. And it's obvious that there's not a magic solution to this or we wouldn't have the problem in the first place. The other thing that we need to think about is there likely will be some advances in technology that can help. One of the things Greg talked about when we introduced this topic was the fact that there's big pores and other places where water can move very quickly. Those are hidden from us. We can't see that driving down the road, but there likely are places on the landscape that are highly sensitive. And so if technology allowed us to actually identify those spots, perhaps we could find some sensitive areas and manage them slightly differently, and that would actually have a large impact.

But at the moment, some kind of like for instance, ground penetrating radar or something of that sort doesn't exist to identify those spots. And so in the meantime, we're going to have to just keep working on this. One of the things that we don't have is a lot of data I've had people suggest, well, if we just had everybody follow best management practices and use recommended rates, I agree, everybody should be following best management practices and using recommended rates. The thing is we don't know how many people there are that aren't doing that so that we can say, yes, if we got this all in line here, it would make X amount of difference. The fact of the matter is if the number of people who are not following BMPs or are over fertilizing is fairly small, then cumulatively that's not going to make a large impact on this in the long run. So we aren't really even sure about that.

Greg Klinger:
Sampling tile lines is valuable because it's sort of a proxy for the water that would be moving to any farm field. It's taking up the gravitational water that moves down through the soil or in some cases up into the tile as well. But so it's just to some extent, it is just an easy way to get access to water leaching out through a farm field versus having to put lysimeters down on the ground and pull that water out.

Jack Wilcox:
Where do you see this issue going in the future?

Brad Carlson:
Well, I think everybody knows that this is being worked on extensively. It's not being ignored. On a big picture standpoint, the state has had a nutrient reduction strategy, which is primarily aimed at surface water that was finalized in 2014. This was put in place for, it's kind of a national, I shouldn't say national, but it's across the Mississippi watershed. The states in the Mississippi watershed have nutrient reduction strategies for the sake of dealing with nitrates in surface water. Minnesota's is set to be rewritten here in 2025, and we currently are working on that. I guess what's important to realize is that the practices that are discussed in the nutrient reduction strategy are pretty much the same thing when we're talking about surface water or groundwater. It's just a different landscape and kind of a different pathway where the water is moving. So that is currently being rewritten.

Now, I'm aware that the EPAs response back to the petition was to direct the state to have a Southeast Minnesota specific plan. At this point, I'm not really sure what that's going to look like considering we already were rewriting pretty much the whole thing for the state of Minnesota. So I guess we're going to just have to sort of stay tuned about that. I guess in the meantime, we're going to continue to do what we do, which is conduct research on this issue as far as nitrogen practices and nitrogen rates and environmental impact. And we're going to continue to do our education. We're looking at having some targeted nitrogen smart meetings in the Southeast Minnesota to discuss how farmers manage nitrogen and how they manage manure on their farms. Like I said, though, we don't know the extent to which people aren't following recommended rates or BMPs, so we're not exactly sure in the long run whether that's going to end up meeting the goals of, I think they basically set the goal of they don't want any contaminated wells anywhere. That's pretty lofty.

Greg Klinger:
So Olmsted County has a county funded cost share program for farmers called the Groundwater Protection and Soil Health Program. It cost shares. So essentially provides some financial assistance to farmers to do various conservation practices. One of the main focuses is cover crops, but it is what I would call kind of a pay for performance approach. And so the idea that this program is based around is that cover crops can pull nitrates out of the soil and prevent them from getting into groundwater, but the degree to which they can do that is sort of, it's pretty proportional on average to the amount of biomass that they're accumulating while they're growing.

Cereal rye that gets terminated when it's five inches tall is accumulating very little nitrogen, whereas a cereal rye that's getting terminated when it's two feet tall is accumulating quite a bit. So that's kind of the basis of it. And so there are different cost share approaches. You have kind of traditional cost share approaches for soil conservation practices, which is basically, we're going to help pay for you to do this thing, whatever it is. Put in cover crops. And this approach is again, pay for performance. And they both have their positives and their negatives with a traditional approach. The person who's terminating a cover crop when it is seven or eight inches tall in the spring in early mid-April, is getting the same cost share as someone who's terminating their cover crop when it's already heading out and has a ton of biomass.

So that's kind of a limitation in terms of pulling nitrate out of the ground. On the other hand, with that traditional approach, sometimes cover crops fail to establish no matter what you do, it just was a bad year for it. They're just not going to establish well residual herbicide impact, whatever it is. So in that sort of sense, a pay for performance approach has the limitation of that. If you don't get the performance, you don't get the payment. And so the way the county program works is they have a minimum height requirement on getting cost share. So you can sign up as a farmer and say, I want to do up to 150 acres of cover crops, and I'll get paid to do this a minimum of $55 an acre if I get that cover crop in the spring or in the fall to 12 inches tall before it's terminated.

And then if I get it to 24 inches tall, they add on another payment. I think $20 an acre. If I plant green, so planting your cash crop into a living cover crop, I get another $10 an acre. And what I really like about the program is that it's very flexible in that they don't have to pick a specific field ahead of time. You could decide, I'm going to do up to 150 acres that's the cap and try and get a 24-inch cover crop, but maybe I'm planting actually 300 acres or 400 acres of cover crops. Some of them will make it to that and they can get certified and I can get maybe a 75 or $85 an acre payment for doing that, and some of them won't. And so it puts the, I think it leads to a situation where people who are really pushing the envelope and have gotten really good at that are going to do better with that program. And that is better for us for water quality.

And of course it's good for the public in terms of protecting groundwater from nitrate, leaching. It also, you get enough of this sort of stuff across the landscape. I think there's a good argument to be made that you serve to have some slightly lower peak flooding and runoff rates across the landscape. And I think as I've been thinking through how this program works, I really think that it can just about anyone in conventional agriculture could make use of it in some way. I was thinking about, you see a lot of fields that have trouble controlling waterhemp, which is a big issue, especially in soybeans in terms of herding yields. So you could imagine a situation where someone has a field where they've had a lot of trouble controlling this weed. Might have a lot of herbicide resistance issues, or you could sign up that field if you're going to go into soybeans this next year for a cover crop and a planting green option.

And maybe you don't have the know-how or the equipment to do that, but maybe your neighbor does who can do that and do it well in such a way that you're not going to have a big issue with yield with your cash crop that you plant into that standing cover. So now all of a sudden you've created something where you can get $85 an acre payment to help you manage that water hemp issue because you're growing a big enough cover crop that it can suppress the germination of that waterhemp. So even for people who aren't maybe necessarily into cover crops for their own sake, I think there is a real good argument that this could be used strategically for just about any farming operation.

Jack Wilcox:
Are there any last words from the group?

Brad Carlson:
I would just say if you're in Southeast Minnesota, keep your ears tuned. We are looking at having some nitrogen smart meetings this winter. The extent to which we cover any of the externalities going on, I guess is to be determined. But at this point, we will be talking about nitrogen and manure management in Southeast locally, so you will have that opportunity.

Jack Wilcox:
All right, that about does it for this episode of the Nutrient Management Podcast. We'd like to thank the Agricultural Fertilizer Research and Education Council or AFREC for supporting the podcast. Thanks for listening.

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