Nitrogen management & groundwater: What to know
Hello. You're listening to advancing nitrogen smart, the podcast series from University of Minnesota Extension. I'm Jack Wilcox at the communications desk here with Extension. Sitting here with me are Daniel Kaiser, nutrient management specialist, and Brad Carlson, educator, both with Extension.
Jack Wilcox:A lot of the conversation about nitrogen management centers around environmental issues and, in particular, reducing nitrates in groundwater and surface water in Minnesota.
Jack Wilcox:Today, we'll talk about groundwater. In the next episode, two weeks from now, we will cover surface water.
Jack Wilcox:Brad, what can you tell us about nitrate levels in groundwater?
Brad Carlson:Well, Jack, the the issue with nitrates and water really kinda starts with the whole, problem with methemoglobinemia, big long word. I'm not even entirely sure that I say it correctly, but that's that's the way I've learned to say it. Some people refer to it as blue baby syndrome, primarily, is a problem with with human infants. And what this is is is, the nitrates in the, human circulatory system can actually rob tissues of oxygen, and so by its basic nature. And so in essence, turning your skin blue because the oxygen in in your blood is what makes it red.
Brad Carlson:Now human adults have, fauna bacteria in our stomachs and our guts that kind of process the the nitrate. And so for most of us, this just simply isn't an issue because if we ingest nitrates and and frankly, there's a lot of nitrate in some of our food also, it's processed and moved into the waste stream, and and it never becomes a problem. But particularly human babies are born with kind of perfect, digestive systems that a lot of the bacteria that aids in the digestive process, they aren't in there. We pick that stuff up through the first six months of life, crawling around, sticking our fingers in our mouths, or all kinds of things that that end up starting that. And so human babies are very susceptible to methemoglobinemia.
Brad Carlson:And so this is, you know, goes back quite a long time. The the original link that was established between high nitrates and water was first published in medical journals in 1945. It's my understanding that, it was, kind of believed that this was a problem, going back to the nineteen thirties. In Minnesota, the first documented case was in 1950, and The, United States actually established the 10 part per million drinking water standard that I think we're all familiar with, as early as 1962. And so that actually predates the Environmental Protection Agency.
Brad Carlson:It's been around for a very long time. You know, I think a lot of people question what what, you know, what effect does this have on adults? Well, probably not a lot. I guess it's worth noting, though, that, as with any, contaminant or, I guess, dare I say, poison, I don't know if that's a great term for nitrates in water, but the issue really turns into dose. And so for every individual, that that dose is gonna be kinda different depend depending on your own metabolism, you know, and and your own immune system.
Brad Carlson:You know, weakened adults, if somebody was, going undergoing cancer treatment and, you know, and had some of that stuff or or if you were, undergoing harsh antibiotics for something that can really mess up the stuff in your stomach, it could make you highly susceptible to nitrates in water also. You know? So it is it is a broader concern, and I think as an overall standpoint, does, you know, as a society, we don't really tolerate, contaminants in our water. You know? And so, you know, it's it's an issue that we've been dealing with for a while.
Brad Carlson:We do get questions from a lot of the public. Well, what what would be considered natural? And I think there's some people that want to suggest, well, maybe this has always been there. If you you look at places where there is not agriculture, if we look at, for instance, Northern Minnesota, other areas where we don't have, crop production, we see that typically the the water, either surface water or shallow groundwater, is probably gonna be at zero. In some cases, maybe as high as, three parts per million, but, really, there's not a lot of nitrate in the environment.
Brad Carlson:And and, you know, we've kinda detailed why in in some of our other episodes why, nitrates originate from, agricultural systems. So that's probably not the topic of the direction we're gonna go with this today. But but we don't expect to see a lot of nitrate if there's not row crop, particularly annual row crop agriculture.
Daniel Kaiser:Yeah, Brad, that's one of the comments, you know, that has come up. What's natural? What was under the Prairies? Because I mean, I generally assume that, you you know, we we look at the data. I mean, it it's pretty low, and that was one of the, you know, one of the questions recently at one of our nitrogen college, from somebody there.
Daniel Kaiser:So I think that's one of the things. If you look at the data, I mean, we know we for annual cropping that we expect some amount of nitrate just because of how the things work in an annual cropping system, but the perennials do tend to clean things up pretty considerably. So that was one of the things that, is being really looked at more, You know, in general, if we start looking at reductions is to try to get something out there in a landscape to keep the, something growing at least there that can take up some of the nitrate because it's really about the only way we can, if we're looking at trying to reduce the risk for loss is, make sure there's something out there that's actively growing that can take up the nitrate itself.
Brad Carlson:You know?, and as far as dealing with nitrate issues in Minnesota, historically, those have been kinda handled on a case by case basis. Now we didn't see widespread problems. I guess it's probably worth noting, you know, we really weren't using nitrogen fertilizers, to a great extent and until the nineteen fifties, it really kinda got started. You know, there there potentially were some issues, relative to, I guess, almost you might almost define as a point source, that being, like a manure cases where there was piles, in the close close proximity of of a well or so forth.
Brad Carlson:But, in general, we didn't see widespread problems in this state, historically. And and when there were problems in a lot of cases, they were shallow wells, sand point wells, and that kind of thing. And so it was kinda handled on a case by case basis. You know? Flash forward in the nineteen eighties, there there got to be a lot more focus on groundwater quality.
Brad Carlson:And particularly at that time, a lot of that attention was was relative to pesticides. The ones that we heard a lot about back in that era were atrazine and and, alichlor, which was known as lasso, But also the other products that particularly were identified were metulichlor and simazine and and metribuzin. And so the the state legislature passed a Groundwater Protection Act in 1989, looking at some of the issues with qual groundwater quality and drinking water quality. And and so, again, a lot of that focus was on pesticides. However, it did also include nitrates as as part of that.
Brad Carlson:And so, at that time, there was sort of a framework put in place on how we deal with these issues. However, that that was, it was it was really kind of a voluntary thing. It was sort of a education and and awareness, situation because we didn't really know how widespread the problems were, and it wasn't even really clear as far as how we were going to, address the issue. You know, the one thing that resulted from the Groundwater Protection Act in 1989 was it directed the University of Minnesota to develop our nitrogen best management practices. And so a lot of the research that went into developing those started, at that point in in, you know, the early nineteen nineties.
Brad Carlson:And I was an undergraduate in college at that time. I actually was an intern at the, research station at Waseca and worked on a lot of those project, just doing grunt labor, taking soil samples and water samples and a lot of that kind of stuff, that you would do when you're an undergraduate intern. But, I was kind of involved with that at that time, and and it it led to eventually the nitrogen BMPs being released, I think, in 1994.
Daniel Kaiser:So one thing about the BMP is that, people should know is they are voluntary right now. And, you know, like, I think that's kind of the concern about regulation. And with, some of this and the fact that the the documents themselves really never meant to be regulatory. However, I mean, they are really put in place to look at, you know, a couple different things. One is what practices that are out there that should reduce the risk as much as possible of nitrate loss to both surface and ground waters.
Daniel Kaiser:But, two, I mean, when we start looking at a lot of this, a lot of these practices that tend to be environmental are also the ones that are most economic for most growers. So the two go hand in hand, and that's one of the I know where we get some criticism on some of these practices, you know, from farmers that they may not necessarily like the practices because they think we're, you know, too focused on the environmental aspect and from the environmental side then there seem like we're too focused on the the economics, but we know they do tend to go hand in hand. And one of the things about these practices, they do need to be updated from time to time, particularly as we see shifts in weather weather patterns, especially rainfall. And that's really the key, with a lot of these practices is it when they were first developed, I mean, you look at the thirty year normals that for the early nineteen nineties, that was from 1960 to the 1990, and we've, you know, seen a pretty significant shift in the total amount of precipitation coming, from when we start looking at these these thirty year normals.
Daniel Kaiser:They do need to be updated. They do tend to need to be focused on current research as much as possible. We're in the process of of looking at that always. You know, their updates aren't coming as quick as some of the research comes in, but because it's a little bit different in terms of how these things are managed and the fact that they are defined in statute. So it isn't anything like we can as an extension employee or, you know, person looking at a lot of this that I can change without going through simple review process. So these things are extensively reviewed, and, again, they're looking at it. So they tie both economics and environmental, you know, issues into these things to come up with these best practices.
Brad Carlson:You know, and and kinda leading up to this, Dan, I think a lot of people are familiar with Minnesota established a small sales tax that is directed towards environmental issues. And so kinda based on that, as well as the evolution of technology that, I think everybody recognizes, the advancement technology going back to the the early nineties when this stuff first, first came out. There was there was a lot of conversation about a decade ago, regarding, kind of bringing a lot of this stuff up to date. There was somewhat of a sense or feeling that potentially some of the problems hadn't, necessarily, alleviated themselves. And so using kind of the modern, GIS technology, there was a decision to to kinda reevaluate stuff.
Brad Carlson:And so the, group got together, was convened by the Department of Agriculture, and they developed what's called the nitrogen fertilizer management plan for Minnesota that was released in 2015. So it's about ten years old now. But it looked at a lot of these nitrate issues as far as trying to identify what parts of the state or where there were likely to be problems and come up with sort of a a systematic process for evaluating whether there was problems, and and again use GIS technology to identify those spots. I think everybody kinda knew, but, I wanted to actually get it on paper as far as how they were being evaluated. And it did set forth a process whereby we've been looking at these numbers and, trying to make some progress in the specific parts of the state where there's issues.
Brad Carlson:If you look at some of the, the data that was produced at that time, they they again, they used the used GIS, databases to try and define places where there was either shallow groundwater or there was, shallow soils which led to bedrock, like, for instance, the Karst area in Southeast Minnesota, where you may only have four feet of topsoil sitting on top of fractured limestone. And then also soils that have a high hydraulic conductivity, meaning like sandy soils where water moves really easily through it. And so they're able to to use, you know, our computer systems to identify these parts of the state. And and, yeah, everybody knew where these areas were, but it was kinda nice to be able to throw it on a map and and to be able to identify that. And so the areas that that came out to be of kind of the highest concern were Southeast Minnesota, of course, the Central Sands area, you know, kind of getting up towards Stearns County and Otter Tail and some of those areas, as well as the, very southwestern tip of the state.
Brad Carlson:There there's a lot of, lost soils that are sitting kind of on top of old gravel. And so if you looked at what the state did is they came in and took those parts of the state, and then they used the the GIS technology to define where there was at least 30% of the crop land was sitting on top of sensitive geology. And so they were able to look at a these on a township level. It's not involving township governments. I mean, I myself am a township clerk, and I know they don't involve the township governments.
Brad Carlson:But a township is kind of a convenient size of, of geography to use. It's six miles by six miles. We know that if you used a county, for instance, for well, first of all, some counties in Minnesota are huge. But in addition, there's some pretty big differences, in some counties. I know earlier in my career, I worked in Rice County.
Brad Carlson:The northeastern corner of that county has, has karst features. There's actually limestone sticking out of the ground in some spots versus the Southwest corner of that county is just very heavy glacial till. And so you wouldn't use a county by county basis, but the township size was, about the right size. And so the the state identified the likely townships that, would be or could be affected, and have potentially high nitrates in their water, and they sent out water test kits to residents to voluntarily send water samples back. And then, of course, they look for elevated nitrate levels in those.
Brad Carlson:And then in places where it did come back as over 10% of the samples that that were returned were, above that, instead of a voluntary, sample, they came back and actually took tests to make sure there was quality control, there wasn't cross contamination of the samples, and so forth. And so from that aspect, they were able to pull a map together of of where we see a lot of the issues with nitrates and groundwater in Minnesota. Not surprisingly, Southeastern Minnesota. However, very specifically, it kinda runs along the ridge where the, if you get towards the river, it's actually so rolling. There actually isn't a lot of agriculture there.
Brad Carlson:It's a lot of forest and land, so not so much issues with that. But when you get in that transition zone onto the, onto the, into the ag areas, they're kind of on the western side of a lot of those counties, Winona and Wabasha and Houston and so forth, where it starts to level out a little bit. That's primarily where we found a lot of the problems. And then, of course, some of the sandy areas like in Dakota County, there were some issues. A lot of people thought there were gonna be bigger problems in the Central Sands area, and it turns out that they really didn't find a lot of big problems in the Central Sands area.
Brad Carlson:Most of those issues tend to be right along the Mississippi River. There you you're coupled with sandy soils together with a with a shallow water table. And so there are some some select problems, in those areas. But but widespread across Central Minnesota and and the and West Central Minnesota didn't see a lot of Minnesota and and, and West Central Minnesota didn't see a lot of huge problems. Southwestern Minnesota, did come up with some high nitrate levels.
Brad Carlson:However, because of the prevalence of public water supplies down there, there really weren't actually all that many private wells to draw from, and so the state kind of backed off from that. And, if you look at the official map now, that part of the state is is car colored gray instead of red, meaning that they just didn't have enough samples down there to reliably say this area is out of out of compliance for nitrates and and drinking water.
Daniel Kaiser:And that far southwest, illustrates one thing I think with the BMPs that, you know, should be known is, you know, we've got the BMPs set into regions. So Southeast, South Central, Southwest, West Central, Northwest, coarse textured soils. They're all separated out in in relatively, geographical areas across the state. But a lot of the when we start talking about best management practices, they're really meant to be soil specific, more than anything else. I mean, really, it's really as much soil specific, but related to some of the underlying principles and with the way that nitrate moves through the soil and, you know, the Far Southwest in Iraq and Pipestone County.
Daniel Kaiser:Meanwhile, you know, Brad identified some there's some issues there that while it's technically in the Southwest West Central BMP region, I mean a lot of those soils would behave pretty similar to what we'd expect with the Southeast. So just because you're in a region doesn't necessarily mean that the soil that you're working on might need a different practice and that's when what is recommended. So the BMPs are kind of a generalized recommendation for these areas but, there may be some adjustments you need to make just based on what you know about the soils that you're working on. So it's kind of I think a good illustration I mean the coarse textured one is another one too that we've got a lot of coarse textured soils that are littered kind of in and amongst a lot of the the other regions that there's some things there that are going to be different from maybe what's recommended. It I think just one of the things to be aware of, when it comes to, you know, some of these goals that we're trying to reach is that I mean, you're gonna see some adjustments have to be made to some of these areas that, it isn't a one size fits all strategy and even within some of these BMP regions.
Brad Carlson:Well, the point you already made, Dan, was that there's been a lot of climate change over the last, thirty years since these things first came came, out to the public. You know, particularly when you look at Southwestern Minnesota, the historic climate averages in Southwestern Minnesota were to be relatively dry. And so even though the soils may have been vulnerable, we didn't think of or or see a lot of issues there, thirty years ago. However, if you look at the rainfall totals over the particularly the last fifteen years, that southern third of the state's been wet all the way to the South Dakota border. And so that's really kind of exacerbated some of the problems in some of these places where we didn't historically think there was a lot of problems.
Brad Carlson:The the other thing, I guess, that that resulted, from the the further investigation of of, drinking water quality in Minnesota was beyond the township. And and and some of that is still it's still being figured out how we're going to deal with that. I know the Department of Agriculture is, kind of in the process of developing some township working groups in some of these places with elevated nitrates, particularly for dealing with some of the rural water issues. But, particularly, the framework was in place, to deal, more directly with public drinking water supplies. And so, they also started focusing, you know, specific plans, some of those areas where there was cities or municipal wells.
Brad Carlson:I guess it's worth noting that, for instance, in Southwest Minnesota, those are public drinking water supplies even though they're not in town. They are serving a large number of residents in rural areas, but also wells that serve larger apartment complexes are considered public, water supplies or if they support a trailer park, and all the residents in one park. Those are also public water, drinking water supplies. And so, they they started investigating some of the nitrate issues with those. And then from that, again, use the GIS technology that we have in place these days to define what they call drinking water supply management areas.
Brad Carlson:The acronym you'll hear people talk about is DWISMA's. And so the these DWISMA's, depending on where they're at with high nitrates, have a much more aggressive plan in place for dealing with high nitrates. They have, because the the areas are fairly well defined, they're able to simply bring in all the farmers, who who are farming land in those areas and develop some specific action plans, in some of those spots. And so there's kind of the expectation that there will be improvement in those areas. And if not, there probably will be some more, aggressive action taken.
Brad Carlson:But I do know for instance, you know, some of the early ones that got worked on, there was some some, changes in crop rotation. Some of those areas got changed to, from row crop production to alfalfa and so forth and did see some early results, better results on that. That, did indeed translate to some of the water problems cleaning up in in some of those municipalities. So that's kind of the status of where we're at with a lot of our our groundwater issues. I think what's important to realize is that a lot of the way we address the the groundwater problems is identical to the way we're addressing the surface water problems.
Brad Carlson:So we'll be talking about surface water in in our next podcast after this. And so, kinda stay tuned. And and in in the end, we kinda wrap this all together into one single action plan.
Jack Wilcox:Brad Carlson, extension educator, and Daniel Kaiser, extension nutrient management specialist. Thanks a lot for being here.
Daniel Kaiser:Thank you.
Jack Wilcox:Do you have a question about something on your farm? Just send us an email here at nutmgmt@umn.edu. Thanks a lot for listening, and we look forward to seeing you next time.
Jack Wilcox:Advancing Nitrogen Smart is proud to be supported by the farm families of Minnesota and their corn checkoff investment through Minnesota Corn.
