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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.
Hello, and welcome to Advancing Nitrogen Smart, the special podcast series from University of Minnesota Extension. I'm Jack Wilcox as always in communications here with Extension.
Jack Wilcox:Today, have with us Brad Carlson, Extension educator out of Mankato, and Melissa Wilson, who's a manure nutrient management specialist out of Saint Paul.
Jack Wilcox:Brad and Melissa, let's just talk a little bit about manure use in general. What are its benefits and challenges?
Brad Carlson:Yeah, well, I think most people recognize that manure primarily is a fertilizer source. I mean, that's how it's treated by most farmers. Manure was often just dealt with as a waste product that needed to be gotten rid of. Had to get it out of the barn or off the farm site and out of site, out of mine. But these days, pretty much everybody using manure is using it as a fertilizer.
Brad Carlson:Whether they're fully crediting or not, I guess that's kind of to be seen, but I think everybody acknowledges it's part of their total crop nutrition package.
Melissa Wilson:Yeah, I'd agree, especially with the way fertilizer prices are these days. If you can get a homegrown nutrient source, so to speak, and that's I'm a little biased, but I like manure as the homegrown nutrient source. It's a lot easier than importing fertilizers.
Brad Carlson:Yeah, for sure. And, historically, there was a benefit for manure application. If you went back like early in my career, we would say, well, when we do comparisons of manure versus commercial fertilizer, the manure always out yields the commercial fertilizer. So then, you know, everybody always said, well, that's because it's improving the soil. This is before the concept of soil health was out there, Or there was some mystery element of manure.
Brad Carlson:I think what we discovered largely the mystery element of manure was actually sulfur. That once we started applying commercial sulfur fertilizer, typically manure yielded about the same as a commercial fertilizer. But that being said, I think we do recognize that a pretty high percentage of what's in a lot of manure is organic and putting organic matter into the soil is good. If we went back to the time of European settlement and a lot of our prairie soils, typically speaking, a lot of our prairie soils were probably at about 12% organic matter, if you went under the Tallgrass Prairie. Kinda hard to define that when so much of it's root matter and living material, what of that is the soil and what's the living perennial plant growing there and so forth.
Brad Carlson:But I think most people generally agree that it was probably about 12% and most of our prairie soils in Southern Minnesota are now three to 4%. Interesting though, when I was in high school or when I was younger, we used to talk about 3% like 3% is where we're at. And nowadays it feels like we're more like four. And so I do think that the reduced tillage and some of the changes in our management practice we actually have built up a little more organic matter than we had say in the 1980s. But we also look at manure application, it's largely organic and it's good for the soil.
Melissa Wilson:Yeah. Especially those manures that have bedding in them. Right? Because bedding usually has a high carbon content, and carbon is one of the things that's helping to feed this oil.
Brad Carlson:Yeah. And, you know, and and then in addition to that, there's, you know, whatever's in there for microbial creatures, I guess. I don't know what the biome or what I don't know what you even call that, but that's an area that we've not really well been able to quantify.
Melissa Wilson:So there's a researcher in the USDA, well, two researchers that reached out, and we did a little just a jar experiment. So they had colleagues from all over the country send soils up to us. And then we had a I think it was just dairy manure, and we did different things to them. So, like, we did different combinations of things that were mic or autoclaved or not. Yeah.
Melissa Wilson:So we autoclaved the manure. We actually autoclaved it three times Okay. Just to make sure.
Brad Carlson:Sure.
Melissa Wilson:We autoclave the soil, and we'll have some living soil, some living manure for no other better term, and did did different mixes of the different combinations. And it was interesting because the soils that had been completely nuked and the manure that had been completely nuked, we found out that the soils never really had anything, but the manure always still had something. So even we tried to autoclave it, and autoclaving means, like, pressure and steam and super high temperature should kill everything, but it didn't in manure. But for the ones where we put the manure, we found out that a lot of the microbiome, the types of things in the manure did not actually last long. Once they were applied to the soil, the soil microbes usually took over.
Melissa Wilson:And I think it's because, you know, in in our gut, it's all anaerobic. Sure. Pretty much in there. And so those are anaerobic species. Once they're in the soil, it's aerobic.
Melissa Wilson:But they all love the nutrients. So even when we did nuke the manure, autoclave the manure, adding the nutrients still increased the soil microbiome.
Brad Carlson:You know, and then there's other things that are in the manure that are not that are organic but not living organisms. There's enzymes and amino acids and stuff like that that is going to feed the existing biome. There's stuff there that's going to, encourage the growth of the existing biome. You know, maybe there's a combination of what you're putting on as well as what the you know, it's kinda like going to the zoo and feeding the animals, I guess, if you will.
Melissa Wilson:Yeah. I joke, or it's kind of one of my things that manure is kinda like a prebiotic plus a multivitamin for your soil. Sure. Because it gives you kind of feeds the microbiome, but it also provides the actual nutrients for them too. Yeah.
Melissa Wilson:But just like multivitamins, you can overdo it and poison yourself.
Brad Carlson:Yeah. You could. You could. You know, but it's also worth noting, you know, we're not we're kinda going down the road of soil health here without really fully going into soil health. We'll need to grab Anna if we're gonna fully on board with that.
Brad Carlson:But the five principles of soil health, one of those is livestock integration and part of that is acknowledging the benefits that manure have for application in our soils. So it is kind of part of the recipe card, if you will, for building soil health. So obviously, manure has a lot of great benefits as far as its uses of fertilizer. I think we also have to acknowledge that there's also challenges with manure too. There's challenges, pretty much my job has been dealing with a lot of the negative consequences of fertilizer application while acknowledging we have to have fertilizer application so we need to talk about what we need and where we need it and so forth.
Brad Carlson:We're just trying to mitigate the problems, but manure, because of the complex nature of manure, it makes it a lot more difficult to manage in an environmentally sensitive way than just simply commercial fertilizer is.
Melissa Wilson:Yeah. And some of that is because of the, like, long term nature, long term release of the nutrients. That means it's less controllable on our time scale versus fertilizers are meant to be used and taken up and actually releases nutrients in one growing season.
Brad Carlson:Right. And, you know, and and then, of course, it also kinda comes into a little bit about what's what's in the manure getting into the water. Really the kind of two things that have been the areas of focus. One has been nitrate because of its link to human health, or very particularly sensitivity of babies, human babies, to high nitrates in water. That is complicated by the fact, like for instance, we find a lot of the high nitrate concentrations in water in Minnesota, in Southeast Minnesota.
Brad Carlson:A recent study by Kevin Kuehner from Department of Ag and some other research partners found that a lot of the water down there is fifteen to twenty years old, meaning it was on the surface fifteen to twenty years ago. And so we're talking about modifying application practices to positively impact water quality, but based on what they found, we're not gonna see the results of that for fifteen to twenty years, which is past the end of my career. And so, the other aspect of that is, though, what we don't really know is because we've been focusing on this for a while, you've been focusing on this for a while, is maybe we've already made a lot of those changes and we just haven't seen it quite yet as far as the water quality impacts on nitrate. You know it's not just a simple problem. Deal a lot with nitrates in surface water and what's running down the Mississippi River, that's a lot more immediate and maybe that's a little more of a yardstick to tell us how we're doing.
Brad Carlson:But that too is really going to vary a lot depending on how wet it is. The years is dry, the nitrate concentrations go way down. The years is wet they go up, know, but now there's some complexity to that and then in addition to that phosphorus is our big water quality concern for surface water It's the limiting nutrient in most of our surface water for plant growth, so adding phosphorus into the water leads to the growth of algae in the water. Just ask anybody who's got themselves all concerned about the reflecting pool in Washington DC in algae and phosphorus. But regardless, phosphorus in the water leads to there being algae in the water.
Brad Carlson:But a big problem with that one is, like we talked about the nitrate issue and some of that water is fifteen-twenty years old, a lot of our lakes that have water quality problems, that phosphorus is in the lake and it's not running out. So even if you shut it off, is in there and it is just kind of cycling around. Manure has a lot of complexity as far as its management goes but the implications of it have a lot of complexity too. So it's not just a simple way to snap our fingers and change manure management, and now we've cleaned up all of our environmental problems.
Melissa Wilson:I think that's kind of the story there, though, is like we didn't realize that we were losing a lot of nutrients until it was fifteen to twenty years down the line, and then we started seeing the issues. Right. So now it's taking time to clean up. And it's not necessarily even just thinking about the cleaning up, and like, we don't wanna have polluted water and stuff. Really, what we're talking about too is lost money.
Melissa Wilson:Like, if you lose nutrients, you have to then pay for those nutrients to put back on your land.
Brad Carlson:Yeah, and this year particularly, that's very poignant. I mean, far as, you know, where fertilizer prices have been the last couple of years, you know, due to a large number of factors. But I mean, in general, it's just anything that goes off the field is just simply inefficiency and one of the areas that I've focused a lot on, I've gotten a lot of mileage out of it to the point where sometimes I feel like I'm beating a dead horse. I've talked a lot about the amount of money spent on fertilizer by the most profitable farmers versus the amount of money spent on fertilizer by the least profitable farmers. But ultimately what it comes down to is the most profitable farmers are using their inputs most efficiently.
Brad Carlson:That's really what it amounts to. So on the manure side it's a lot more difficult track that on a dollars and cents basis because you didn't buy the product, it's a byproduct of the livestock operation, how does the manure handling an expense of the manure, is it an expense of the livestock, You know, there's all this complicated nature, but, you know, the bottom line is, is if it's going off-site, it's inefficient use of the nutrients.
Melissa Wilson:Yeah, I like to put it this way. I joke that feed is pre manure. Right. So, like, you did pay for the feed, so you're paid for that to come onto your farm, so why not use the nutrients the most efficiently way possible?
Brad Carlson:Yeah. And and so the state, if you're going back to the nitrate thing, the the state has done some pretty significant monitoring of nitrates in groundwater. One of the things that I found really interesting is I just wrapped up writing a what's that? At least in its present form, it's a 27 page publication on nitrate issues in Southeast Minnesota. Now depending on when you're listening to this podcast, this is the first time you've heard that or maybe you've already read it already, depending on where things are at.
Brad Carlson:But you talk about, you know, we didn't know, okay, we don't have a baseline of water quality data that predates roughly speaking about 1982. That we were not comprehensively monitoring water quality, groundwater quality, there's sporadic surface water readings in various places, but it wasn't done. It was like grab samples, let's just find out what's in here. It wasn't done for the sake of let's establish a baseline. And so it's very difficult to monitor progress when you don't really know where you're starting from.
Brad Carlson:And so if we think we started already at the point where there was a problem, now we're not quite sure where we're trying to get. For instance, we don't know what those numbers looked like in 1930 or 1910, you know, before we had a lot of animals out there and the role that that might have played.
Melissa Wilson:Yeah. I think that's important to remember too, is that we don't necessarily know the trends over time, over, like, the long distance time, but we do know that there are goals that we would like to meet. We would like to have good water quality for people to drink, good water quality for fisheries and recreation.
Brad Carlson:The one thing I will say is, so in the Southeast, a number of counties started pulling their water quality monitoring data about 1982 and I've got a copy of that database, from about '82, I'm trying to remember the date, it was like '82 to '88, And not in all of the counties in the Southeast, but in most of them, if you look at the number of samples that went through the testing lab in Rochester that tested over 10 parts per million, it was like 14.2, something like that. Now the State Department of Agriculture initiated a township well testing program back about a decade or so ago, a little longer ago. And if you look at the total number of wells testing high in that program, it's like 13.8 or something like that. Essence, the numbers today are almost identical to what they were in the eighty's. Now obviously that tells us it's not getting a lot better, but it's not getting a lot worse either.
Brad Carlson:We can at least hang our hats on that, that this isn't a growing problem and hopefully that tells us that we've stabilized and we can kinda start working on it from here. What's kinda fascinating is if you look at that township testing data, there's really like two bands that really stick out and one is kind of on the fringe, so if you look at Southeast Minnesota, of course the Mississippi River bounds it on the East and then there's kind of a western boundary that's not really visible to the naked eye but it's based on soil types. The part of the Southeast that most frequently tests high is a strip that runs on the edge of bluff country. So when you get farther east, you end up with a lot of land that's not even farmland. So we know that nitrate loss from forests and that kind of land is almost zero, so we don't see a lot of water quality issues when you get right towards the river.
Brad Carlson:When you go farther west we end up with deeper soils, we don't have quite the same issues either. Now if you flip flop and you go north of the metro area, now we know that there is the Central Sands part of the state and of course I think a lot of us thought there were going to be a lot of water quality issues in the Central Sands and there are some. But in general, the majority of the townships that are testing really high are kind of right on the Mississippi River. So it's sort of a combination of not just simply having sandy soil but also having high water tables. That's really kind of the places.
Brad Carlson:Now, if you take the map of the places that are testing high, the townships that are testing high for nitrate and the Department of Ag is defining that as 10% of the tests are above 10 parts per million. And you compare that to a map of feedlots, registered feedlots in the state where each feedlot is just a dot, but of course that map gets darker the more feed lots there are, they kind of overlay each other. Now the tendency might be to say well see we've got a relationship here between the feed lots are causing the water quality problems. But those of us who really deal in agriculture know there is something else there and that is the landscapes that tend to favor water quality issues are the landscapes that don't lend themselves well to broad acre row crop production and we end up seeing a lot more livestock because that's economically one of the only systems that's gonna work in those areas and so it's sort of an incidental of the livestock, a lot of livestock is getting concentrated in a lot of these landscapes that tend to be more sensitive, not that the presence of the livestock is causing the problem, however they tend to be both in the same places.
Brad Carlson:So that kind of leads to the need to just simply be a lot more sensitive with how we are managing manure in those parts of the state because it just so happens that there is a lot more livestock in some of those places where we're getting high nitrate levels in some of that well water. When you go across the rest of the state, we don't really see the nitrate issues, think we see a lot of the more the phosphorus issues. That again gets into, like I said earlier, some of this complication of, are we still putting phosphorus in that water, or is it there from seventy years ago and it just gets recycled by carp and water weeds every year and it just never leaves the system. I don't think we got a good answer for that. I mean, there's been investigations in some water bodies that's kind of looked into that and I think there's a general feeling a lot of those places are slowly getting better over time.
Brad Carlson:But then we've also got a little problem spot in the Southwestern corner of the state that's there's a lot of beef down there but we've also got lost soils and while in the Southeastern area, we've got these less soils around top of karst on limestone and the Southwestern corner of the state, a lot of those less soils are sitting on top of gravel. So just similarly, also sensitive. So, you know, we've got a lot of challenges that we need to work with just that are just sort of inherent in the system. We've got a lot of animals in a lot of places that are sensitive to water quality concerns.
Melissa Wilson:Yeah. I think just making sure you're following the best management practices for mineral application, hopefully make you more efficient at getting those nutrients back in the crop, and then that has the added benefit of keeping them out of our waterways.
Brad Carlson:Yep, and we're just gonna continue to refine our management practices, hopefully technology gets us a lot better as far as getting, nailing down the exact amounts and timings of the four Rs basically. And, you know, and potentially, there could be some other things you're working on in season application and so forth. So, you know, I guess as time goes by, we hope to just continue to make gradual improvement on this.
Melissa Wilson:And I think there's a lot of that coming, too. Like you said, just with the way prices are, there's a lot more people looking at Manure, and how can we use it efficiently? So we're seeing, like, the irrigation systems that can go out and apply every couple of weeks, right, on the corn plant. We're starting to see, as applied nutrient sensors for manure so you can map out what the nutrient content looks like as you apply it across the field. We're looking at more precision weight distribution systems, so that way you know exactly how much manure you're applying for your poultry litter.
Melissa Wilson:So there's all kinds of cool up and coming stuff.
Brad Carlson:I agree, and I I think, you know, ultimately, I think probably, you know, today, what are we asking of farmers today? I think it's just arm yourself with knowledge of what's going on, what the actual water quality issues are, and then do the best job you can. I mean, get as much information as you can, do the best job as you can, keep abreast of some of these technologies as they're being researched and developed, and this probably is going to evolve over time.
Jack Wilcox:Thank you very much. Brad Carlson, Extension Educator out of Mankato, and Melissa Wilson, Extension Manure Nutrient Management Specialist out of Saint Paul. We appreciate the information.
Brad Carlson:Thank you.
Melissa Wilson: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.