From Slurry to Science: Making Manure Data Work for You

In this episode, Dan Andersen dives into ManureDB, a tool from the University of Minnesota, which analyzes manure samples from across the United States. Dan discusses the nutrient composition of various manures, the impact of storage type and climate on nutrient concentrations, and the importance of manure sampling. 

Visit ManureDB at: http://manuredb.umn.edu/

Show notes can be found here

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Okay, so the next thing that I wanted to look at, and probably of more interest to most of you, is what, how does storage type play into this? All right, so within the liquid manure samples, they were categorized into four different storage types. There were covered pits or tanks, earthen basins, lagoons and uncovered pits or tanks. Now each type is farmer reported, right? So if I said I had an earthen basin, I'm not sure inherently, it means something different than a lagoon, right? It all depends on how that farmer classified it. I would say to me, they're slightly different than that. If I have an earthen basin, I'm trying to pump it as low as I can when I'm emptying that storage to make sure I have capacity to make it to the next application window. If I have a lagoon, I'm trying to leave some residual treatment volume in there so that I can encourage solids breakdown moving forward. Now that doesn't mean that's how it was classified by farmers, but with that said, one of the things that stood up pretty remarkably to me in this analysis, is those covered pits and tanks, uncovered pits and tanks and even Earth and basins had solids content above 5% right? So they're in that five to almost 6% range. Lagoons were much more dilute, about three and a half percent solids on average. Again, huge variation within a storage type, but there's a sufficient date in here to start saying that there was at least statistical differences. So that would tend to say that at least people who reported this, when they said they had a lagoon, they're probably thinking about it as a system that had a fair amount of water where there was some dilution occurring, and it really was maybe more of that treatment scenario. If they said they had an earthen basin, they really were trying to think about holding it up and trying to pump all the solids out, probably with some agitation. The other thing that stood out to me is covered pits and tanks, earth and basins and the uncovered pit and tank, those solids content were more typical of what we saw when we said that a system was going to be agitated. Those samples that were classified as lagoon here, they looked like those solids where people said they weren't agitating. And that sort of fits with the management scenario that we had in mind, right? Those tanks, pits, earth and basins, we think people will be agitating them, lagoons, well, maybe less so because of how they're managed, how we're using them, and maybe what we're putting them on. So it fits with our conceptualization of maybe what these manure management systems look like. You. All right. Now the fun part, when I looked at total nitrogen content, there was a difference, right? So covered pits and uncovered pits both tested 20, 21, pounds of total nitrogen per 1000 gallons. You might say, well, I'd expect a covered pit to do a little better for total nitrogen. It wasn't statistically different. It did trend a little higher, but it definitely came through for ammonium nitrogen that the covered storage was higher. It had 15 pounds of ammonical nitrogen per 1000 gallons, as compared to that uncovered pit or tank, where it was down around 11, right? So it was holding more nitrogen by having it covered, but not necessarily more total nitrogen in the manure, which was was interesting. The other thing that stood out here is that both earthen basin and lagoons tended to be lower than those either covered or uncovered tanks or pits. Lagoons were down at that 15 pounds per 1000 gallons total nitrogen. About 10 of that was was in the ammonium form. Earth and basins tended to have a little bit more nitrogen in them, about 17 and a half pounds of nitrogen per 1000 gallons, and about the same amount of ammonia. So that's that's that's sort of how we would conceptualize these things. Tanks tend to have less surface area to volume ratio. Probably do a better job of conserving nitrogen. Earthen and basins, and especially lagoons tend to get relatively large surface area to volume ratios, and maybe we have more volatilization risk. And that's essentially what this said for the nitrogen story, right? Tanks, either covered or uncovered, had more nitrogen in them, if you're getting it that nitrogen converted to ammonia during storage, covering your tank holds on to more of that ammonium nitrogen, so more of that right available, right way, available plant fertilizer. And if I'm using earthen in storage, you're probably seeing that nitrogen content come down a little bit. And the truth is, most of the other parameters of phosphorus, potassium, sulfur, tended to follow what we saw for nitrogen, but at a much more subdued range, right? So phosphorus tested right around eight pounds of P2O5, per 1000 gallons for those tanks, and even the earth and manure storage for that lagoon, it was down near six. Potassium was up in that 15 to 20 range. 15 for lagoons, 20 more for those well maintained, covered storages that probably didn't have as much water influence on them. Wow, this is way different than what we expected. And on the other hand, it's sitting there and saying, yeah, it's it's about what you'd expect for these different types of systems. But look, there's a lot of data behind it to show you that it is working roughly how we think it should be working. So just to summarize a little bit, there covered pits retain more ammonia. Lagoons are pretty dilute across the board, and earthen basins fall somewhere in the middle between those tanks and lagoons, which is about where we'd expect them to fall. Again, much of that nutrient variation is tied up in that story of what the solids content of the manure is. So when we say that tanks did a better job. They had more nitrogen in them. Well, a lot of it's related to, you know, what the solids whatever content of the manure was starting with. And then the last thing I wanted to look at was a little bit of climate's role. And this is a little bit harder to do for a couple reasons. One, I don't know where any facility is located, and because of that, I didn't want to look at any annual variation, right? When I look at this, the only thing I could look at is, what were state averages? So I could, you could say, well, you should look at Iowa State average as a function of time and trying to collect for the weather we saw in Iowa. And that's probably it into a into a pile and try and stack it up, it gets a great. I maybe could do that. It's a lot of work. And when I But it does give us, on average, higher solids concentration. And as we talked about earlier, many of the nutrient concentrations were correlated to total solids, so it tends to come through on at least a few more of those parameters than just total look at the state of Iowa, some years, the northern part of the solids. It also indicates that maybe in Iowa, we won't see much as much of advantage from putting a cover on, having that covered pit or tank to keep rainfall out as what we see in state is really dry. Southern part of the state is really wet. some of those other states where they tend to get some more rainfall. Now, again, cases can vary in years, vary a lot. If you were in a drought like we had, from maybe 2020 to 2023 you probably didn't worry about whole lot about rainfall if we So it's hard to make heads or tails of that without knowing get a wet year. I think back to 2014 2016 2008 maybe the spring of 2024, in northwest Iowa. Well, maybe those covers would some details about where the facilities are located and how have done something really helpful for us in some of those years and keeping rainwater out. But it is really a long term decision, and I think we need to continue to see people putting correct to correct for location. On the other hand, when we take samples in to say this is what I had with my covered manure storage, to really show what the impact that might be. So if you are looking for some helpful graphics to understand what I was talking about in terms of some of those trends, make sure all the way back from the year 2000 to 2023 which is, I think, you do check out the show notes as I tried to share some of the key highlights and some of the figures that I generated to help understand some of these situations. Because I know numbers come fast, and I'm trying to highlight just the the last year in the database, when I downloaded it and say, main trends here, but sometimes we care about those numbers, or want to see what they look like. So I wanted to give a few key takeaways from what we saw from those liquid manure samples. Before I I tried to dive into maybe talking about a few of What were these states on average, the long term climactic those solid manures and what we were seeing. So one of the things I want to point out is that good testing is essential. While I can say, on average, this storage had more solids, a averages tend to be relatively stable, and maybe we can do a higher solids content, or more nitrogen than another one. There's a huge amount of variation within each category type, so it really is important to get this information for your farm and trying to get it local to what your conditions are better job. So the thing I wanted to point out here is really like. The other thing I wanted to point out is that solids testing is essential. If I know nothing else about manure. It's really easy for me to think in terms of how thick there's a strong correlation between wetter states having is it. Are we doing a good job with water conservation? Are we doing a poor water job with water conservation? And since many of these parameters are tied to that solids content, or lower solids content and drier states having a higher solids content. So specifically, to get a handle on that, I used a program called animal waste management. It's a little computer program put out by NRCS. It is really designed to help you size a manure storage. But what I like about it here is it automates the process of looking up that some of that climatic data. What it lets you do is pick a county within a state, and it will tell you the long term average rainfall in that county and the potential evapotranspiration in that county. And since it automates it, I don't have to do anything other than figure out roughly what county is in that center of the state or the centroid of the state. So for each state in the database, I looked up the county that was the center of the state, and then I use that animal waste management program to get what annual precipitation would be, an annual evaporation potential would be. So I took that precipitation minus evaporation potential. So that's a positive number, it's an indication that it thinks that there will be dilution water added to the manure. If it's a negative number, it says, Well, pretty good slump. I think about this coming out of the dairy farm where I grew up, maybe some days we had to stockpile a you could be thickening your manure. You could be evaporating little manure and but it was a semi solid so we would put it in a pile, and the next day that pile would be a lot wider than it was tall. It really had some slump. So that might be scraped more. Water than you're getting. Don't take that quite at face manure that has too much wet bedding in it to be a true liquid, but too much water in it to be a stackable product. It shouldn't be pumpable, would be my definition. And you're going to try and put it in some sort of pile or bunker, knowing that value. Things like a crust on your manure storage might reduce the pile doesn't work very well and the bunker is probably soggy. Now, with that said, when I talk about the results, it was drier than what people classified as salad manure. So I'm not quite sure sort of what it represents on every farm, but evaporation and they don't stop rainfall from going in. On the at least to me, that's what I would think it would represent. The next category was separated salads. Again, this is, this is an easier one to say what it is that's something where someone is using a separator, some type, whether that be a screw, press, other hand, it's a pretty good indicator of what the potential roller, press, slope, screen, belt, press what have you they're doing some separation to get a solid, and then they have a liquid that flows on to the rest of their storage. Another is in an area. So even if I was in Iowa and I wasn't getting one was sludge, and sludge, I think, has a pretty good definition. It's that stuff at the bottom of the tank, when we have to quit pumping out the liquids that we just can't get and we start scooping out. So probably a little bit more that full evaporation potential of what it says I could as long liquidy, but we're going to call it sludge, because it was those heavy solids. You probably aren't removing it that frequently every year, but it's coming out of the bottom of as roughly we're getting the same evaporation percentage of their storage so at least know where it's from and have a good idea of what people probably mean. Another category was just called solid manure. That was a, probably a generic catch all of, hey, it's a solid material. It's not pumpable. It's not that semi solid. Where I think about it's hard to manage. It's it's our evaporation potential is in Iowa as we do in Ohio. It's probably stackable. And in my mind, I tend to think of things like bed pack manure right now. That doesn't mean that's the only thing it is. It could be things from a tie stall barn. It probably a pretty good assumption, or at least it could be things from sort of that composting barn, if they decided not to call that a compost for whatever reason. But it is sort of that that catch all of what's left here. And should work out relatively well for me. So I took that and I then there was a bunch of samples that were just unlabeled, and who knows, it's whatever they were. The farmer didn't fill out that category. Maybe the lab didn't have them categorize what it was, and then they get lumped into this said, I'm going to plot that precipitation minus evaporation category. So if you were sending out manure samples and you want to help manure database get more accurate, more specific to different types of manure systems. Filling out that information is handy, especially moving forward when you know on the x axis there, and then I plotted what's the total solids this is a resource out there to try and lock down what typical things might look like. I know it's sometimes a pain, but hopefully spending that couple extra minutes to make a check mark on your lab entry form or write it in so that it can help concentration on average in dairy manure storages in this out this database and give you something to benchmark against in the future, could be helpful and worth doing for you. So a little call to action there. All right, so what did the nutrient data? Data say? And I tried to look at this in a couple ways. state on the Y axis. And that balance described about 80, 86% One was sort of just what raw nutrient concentrations were on average, and then another, where I corrected for solids content, just like with the liquid nors, we saw that solids content was pretty. Good explaining the variation that was going on. It of the variation in the manures total, in the average manures didn't maybe change the results as much as what I saw when I was trying to understand it for liquid manure, but it did bring them together and put them more in the same range there, where total solids concentration for the state. And that's really, it provided some things going on. So a couple things for you here with what people called solid manure from dairy facilities. We were generally in that 35 to 45% solids range on really strong, right? And I think that goes to what we've average. Now we saw things that were really dry 80 to 90% solids. We did see things that got down in that 15% solids range when you look at individual samples, but all probably always would guess. Now in the past, I've just told those categories on average, were typically somewhere between that 35 and 45% range. Things that we saw were compost samples tend to be drier, separated solids tend to be wetter, and people, well, Iowa, we have better manure, and in this that's not a surprise, right? When you run a screw press, it does come out pretty wet. We're squeezing it hard, but it's hard to get water out of some of that material. Putting in a compost pile, where it heats up, blows off some of that water, we get database, story tended to look pretty true. In our case, it good evaporation potential. It tends to dry us out. All right, a couple other things on here. Ammonia concentration is no surprise in all these samples tends to be relatively low, somewhere between one and three pounds of nitrogen as ammonia would say it was mostly true because of maybe we had some per ton of manure. Again, we saw some differences. Compost samples tended to be low, separated solids tended to be low. Things that we were thinking about as manure, higher evaporation potential relative to rainfall compared to digested solids or that bed pack material, tended to be more on the higher side of that three pounds per nitrogen range in terms of total nitrogen, we were talking anywhere between 10 and the other states. 20 pounds of total nitrogen per ton. No surprise, right? More of that organic material was down there, and we were scooping it out and getting it out to the field, things like compost, where we'd done a nice job breaking it down, getting rid of some of that carbon material, or that bulking material, also tended to be pretty high. Separated solids tended to be in that low category. For how much nitrogen there was about half 10 pounds of nitrogen per 1000 gallons, rather or per ton, rather than 20 pounds per ton. When we talked about those liquid manures, we saw somewhere around 55, 60% of our total nitrogen, that ammonium form. When we think about solid manures, it is much, much lower. I'd say a good number, on average, was somewhere in that 20 to 30% range. But some of these things, compost, specifically, was only about 5% ammonia. Almost all that nitrogen was in some stable form. We'd see some variation in phosphorus content with different manure storages. I know when people ask me how much phosphorus is in a dairy manure, solid dairy manure, I tend to say 1012, pounds of phosphorus per ton. And I think in general, that tends to be what I saw here. The solo manure category came right out at 10. But we did see some variation where compost was up to 13. Those digested solids were up in 15. So there are some places where we see that a little bit higher. And then if there's places that are higher, there's got to be some places that are lower, right? So those separated solids were down at eight. So we did see some variation there as well. Again, correcting for solids content, sort of brought these in the same range, and they make me say, feel better about saying 1012, pounds of phosphorus per per ton is a pretty good place to think, but tremendous variation. But at least this database, and hopefully the show notes, where I give some of the Summarized tables, will give you some ideas of where things are falling. So a few key takeaways here for you. One, if you're using solid dairy manure, don't assume it's all the same. Compost isn't just old poop. It's low in ammonia, but very rich and stable nitrogen and a little bit enriched in those other nutrient fractions as well, because we've done a good job of hopefully breaking down on some of that solid material. Digested solids tend to be more nutrient dense than people think, and separated solids, well, we get a lot of that organic material, a lot of that structure building material for soils, but we're not always pulling a lot of fertility out. Now, with that said, it can be fertility that matters. Oftentimes it's phosphorus instead of nitrogen, but it tends to be more of that carbon material, and I think that's what people have tended to say over the years, unless we're really getting into some of that specialized separation equipment, again, just like we saw with the liquid know, the system you're dealing with, and test your manure, solids content and source explain a lot of that variation that we're seeing and help us Understand the nutrient punch that manure will be supplying, but it's important to get that manure specific for your farm and understand what your management this year did for it. So some things I can say with relative certainty, compost tends to have stable nutrients, and we're thinking about more long term fertility, fertility, not immediate fertility, digested solids, they're still valuable, especially for phosphorus content sludge. I know it's messy, a pain to deal with sometimes, but it did, on average here, look pretty powerful in terms of nutrient supplying power. So I just wanted to end today with a little call to action. I think while manure database is still in the early stages, it does have potential to be a really powerful tool. And helping us understand the nutrient compositions of different manure and the variations that people see, and also help us understand what's typical nutrient content for different styles of manure and management systems, which is what we all are asking and want to know so that we can make data driven, informed decisions. So if you want to some rank them the manure database, one thing you can do is make sure that your samples get submitted and make your manure matter. Along with that, good labeling, lets us know what's going on, helps us understand how to classify that and get the most out of the data. So with that, we look forward to hopefully having you tune in next time where I plan to talk about manure foam and some of the issues associated with that, along with the causes. 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 talkin' crap.