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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 back to Advancing Nitrogen Smart, a special podcast series from University of Minnesota Extension. I am Jack Wilcox, as always I'm in Extension Communications.
Jack Wilcox:Today, I am here with Brad Carlson, who's an Extension Educator out of Mankato, and Melissa Wilson, who's an Extension Manure Nutrient Management Specialist here in St. Paul.
Jack Wilcox:Melissa, what is manure really? And what has to happen for it to be usable? We probably all know the answer at a basic level, but I'm sure there's more to manure that many people don't think about right away.
Melissa Wilson:So I always enjoy asking this question when I'm out giving talks. We say, kind of ask the crowd what is manure and a lot are like nutrients and microbes and stuff, but I'm thinking about physically, like what goes into it? What are the things...
Brad Carlson:You're thinking literally.
Melissa Wilson:Yes. Literally. And it's the feces and urine.
Melissa Wilson:That's mostly what makes up of it. But a lot of times people aren't thinking about the wasted feed, the wasted water, and then bedding too, if there's bedding in it. So it's really a combination of a lot of different things.
Brad Carlson:Yeah, and when you think about it, I mean, you know, it's the animals pee and poop, okay? So we think about the feces part. I mean, it's generally speaking, it's solid and it kind of, you know, we're going to talk a little bit later about how it gets stored and handled, but, you know, you're combining a couple of different materials. But when we think about solid stuff, you know, it's going to be highly organic and, you know, we think about fibers and bedding and things that animals eat and so forth. And so, you know, some of that stuff is going to be in its more degraded form.
Brad Carlson:I think we realize that when that passes through the digestive system, it gets broken down. I mean, the animal and we as humans, we extract nutrition out of that. So it's just quite literally what's left afterwards that that process is not, you know, 100% efficient. So there's going to be some stuff left that maybe the animal could have made some use out of, but there's gonna be a lot of it that it wasn't able to make use out of. And so there's gonna be this big combination of things in various states of decay, if you will.
Melissa Wilson:One of the interesting things is that a lot of the nutrients actually come out. So like Brad said, they're just not efficient digesters. It's something like on average, 75% of what goes in comes back out. So that's nitrogen, phosphorus, potassium, whatever it may be.
Brad Carlson:Well, the other thing, of course, is on the urine side, you know, that, of course, is obviously it's liquid, but you're going to be dealing primarily with inorganic nutrients with that. And so we're also dealing with this sort of proportion of how much of that is in with the feces.
Melissa Wilson:And that certainly changes by animal too. Some tend to defecate more and some tend to urinate more than other animals.
Brad Carlson:Yeah, and not only that, but then it also is gonna be dependent on the system that they're housed in because, you know, some of the, you know, we are aware that cattle frequently are more inclined to be out on lots and hogs are typically standing right on top of their manure storage. And so with hogs, we're usually collecting almost all of the urine. A lot of the cow urine is ending up on the ground and it's not ever really reaching in, getting its way into the manure storage in a lot of cases. And so, in those cases where a lot of that's ammonia that's in there and it's in contact with the ground, it's got the chance of either absorbing into the ground or just volatilizing and blowing off also.
Melissa Wilson:That's the thing with urine. The nitrogen in it is technically organic as it comes out, but it is like really fast release, changes to urea.
Brad Carlson:Urine, urea, yep.
Melissa Wilson:Most animals is coming out as urea, the birds is coming out as uric acid. That's why there's also a little bit of difference between birds and other animals too.
Brad Carlson:Sure. And so, you know, really the process of nutrient release out of manure is going to have some similarities to the mineralization of nitrogen just out of our soil organic matter. However, obviously the soil organic matter is this kind of long time, long running pool of complex biological organic compounds that just releases slowly. And of course, because the manure just recently ran through an animal's digestive system, we're not dealing with the slow release and the mineralization like we would out of soil organic matter.
Melissa Wilson:There is some that is slower, though. We do have some that'll take maybe one to two years, but you're right. The organic matter in the soil is in a longer timeframe.
Brad Carlson:Yeah, and sometimes I guess we also kind of think about, I mean, kind of the old time theory on manure application, a lot of farmers wanted to put manure on their quote unquote poorer ground to build the soil. Well, obviously, the thought there is we're building organic matter, so there's gonna be something in there that's longer, much longer live if we're trying to build organic matter. I don't know that we've really got a ton of research that really goes into that as far as saying that if you've got eroded soils or sandy soils and you're targeting your manure applications there, are we really building soil organic matter in those places? Well, it's not going to hurt, of course, but I can't say that we can really put a number on that either.
Melissa Wilson:No, but we do know that there is long term benefits of manure application. I have these trials up in Western and kind of Northwestern Minnesota that we applied manure on twice in a six year period. And we've seen those kind of long term benefits compared to the plots where we didn't have manure at all. Yeah. So there is definitely a long term benefit.
Brad Carlson:Yeah. I think a lot of farmers have known that instinctively for a long time. Of course, there's also always been that competing problem of how far away do you have to drive from the barn to do the application and what's the weather like, what are the soils like, is it raining, what other work do I have to get done and so forth. But, you know, I think in a perfect world, you know, if we looked at my dad's and my grandfather's generation, you know, they wanted to put manure. They weren't always even necessarily crediting the nutrient in the manure, but they just simply looked at, well, we put the manure on the poor ground, that's where it does the most good.
Brad Carlson:Yeah, absolutely. And so we start looking at this kind of this distribution of what's organic and inorganic as it comes out of the animal. I think most farmers using manure are pretty well aware that there's some pretty significant differences as we go from one species to the next. And, you know, we already mentioned the fact that the holding facilities for the manure are an important factor. Pigs, of course, are usually these days are standing on top of their manure storage.
Brad Carlson:Maybe there's a few farrowing facilities still out there that have outdoor storage, and those are a separate problem because they're collecting rainwater versus a lot of the cattle, which spent a lot of their time standing on the ground and were tending to try and scrape the manure or push it into manure storage instead of it actually falling there. And so we end up getting a pretty big disparity between how much is organic and inorganic in those types of manure.
Melissa Wilson:Yeah, we collected data from a couple of Upper Midwest labs. They sent us the total nitrogen versus the inorganics, so the ammonium nitrogen. So we split it out into two components. It's total nitrogen and then inorganic versus organic. And we found that in a lot of liquid manures, it's at least fiftyfifty inorganic ends.
Melissa Wilson:There's at least 50% of that is ammonium, which is plant available right away. In swine, was even more. On average, on these samples, was 75%. And I know I've seen lab samples come back 80%, 90% ammonium.
Brad Carlson:Yeah, it's probably worth mentioning that what is organic in there probably, as you mentioned before, if it's in, if it's urea, it's probably going to be quickly converting anyway. So it's not just a matter of it being a highly inorganic, it's the stuff that is organic is not long lived organic compounds.
Melissa Wilson:Yeah. So like dairy and beef, they average around fiftyfifty. Swine is 75. But if you move down into the solid manures, there isn't anything that's over 26% in organic nitrogen. That's turkey litter. Or poultry litter
Brad Carlson:Well, in you know, and then there's some factors involved in that because, you know, for one thing, solid manure usually includes quite a bit of bedding. So,
Melissa Wilson:And the bedding ties up some of that nitrogen.
Brad Carlson:It ties up some of it. The bedding itself has some nitrogen. Some of that's got that kind of high carbon to nitrogen ratio itself. And so those tend to be slow chains to break down. And then in addition to that, of course, that's usually stored outside in the elements.
Brad Carlson:And so, one of the common products we already mentioned, we got urea turns into ammonia and that volatilizes and blows away. So then a lot of what would have been the organic is just lost, you know, through to the air. So that's a pretty significant component also. One of the challenges though that I've always dealt with is getting a good manure sample. That's not our topic today, But you know, when we've got all that bedding, you know, there's obviously there's your cow pie and then there's your chunks of straw.
Brad Carlson:And it's how do we make sure that we even got all that in there? But that's, you know, that's also explains some of the wide variation and inconsistency when we look at the analysis of solvent are also.
Melissa Wilson:Yeah, absolutely. When you talk to labs and talk about how they try to keep consistent even within the sample they're sent, Some try to mix it up. Some try to do like an equal proportion. Like I'm just going to grab little samples from four little areas in here. So even within the lab, they're trying to capture some of that variability.
Brad Carlson:Yeah. And then of course, you mentioned poultry, that's also got its own special problem because that's frequently using wood chips as bedding. And that's like way off the scale on that carbon to nitrogen ratio. And then beyond that even, a lot of that is composted and that's adding to some of the complexity. Some of that stuff, depending on the seasonality of it and when they're emptying the barns can be really fresh and kind of hot, and others of it's been sitting for months before it actually gets on the field.
Melissa Wilson:Yeah, that's always a fun story to talk about too, is even though the inorganic nitrogen is low of the total nitrogen, a low percentage, there's still a lot of ammonia left in that manure. I don't know if you've ever dug around in a in a fresh poultry litter pile.
Brad Carlson:Smoke coming off of...
Melissa Wilson:Yeah. I'm pretty sure I've burned my nose hairs out sometimes. So So just because it's a low proportion doesn't mean there's not a lot for your crop too. It's just that it takes longer for it to release over time.
Brad Carlson:And so when the manure gets applied, you know, obviously the whatever is going on that's inorganic is just immediately available, crop available. Of course, you know, put an asterisk on that because of course there's all of your other factors involving availability. If it's ammonium, did it end up getting adsorbing to a clay particle? If it's nitrate, that's sort of dependent usually on water movement into the plant. And so of course, if it's really dry, this is going to sit there and so forth.
Brad Carlson:But that being said, those compounds, those inorganic compounds are readily available once they're put on the, applied to the field. And then the organic stuff, we have to kind of play the waiting game.
Melissa Wilson:Yep. And that takes, like there are some molecules in there that can be broken down by this little microbes pretty quickly, like few days, weeks. So there's kind of a mineralization factor that we talk about happening in that first year, and then there's one in that second year. Some of these manures might go three or four years, but the vast majority happens in the first two years.
Brad Carlson:Yeah, and a topic we've talked about in the past with our Nitrogen Smart stuff, maybe not so much in the manure context as we have with commercial fertilizer, you know, there tends to be this myth that the nitrogen has to be in the nitrate form for the plant to pick it up. The majority of the nitrogen that's picked up by the plant is in the nitrate form, and that's primarily because the majority of the available nitrogen is also in the nitrate form, and that's kind of what's there. But the plants will pick up ammonium just fine. They'll use the same exchange processes they use to pick up potassium or some of the micronutrients and so forth. And so those inorganic forms are quickly moved in.
Brad Carlson:You know, the organic stuff, the plant itself really can't take up and use organic molecules. Those do have to break down before they're available as plant nutrition. And so, you know, then that being said, you know, there's obviously going to be some management differences depending on what we just talked about, that proportionality of how much is organic and how much is inorganic. And so it's one of the reasons why a lot of farmers, Southern Minnesota and Northern Iowa have built hog barns when you don't see them anywhere near a farm. And of course, some people are like, Oh yeah, well, it's so they don't have to smell them at home.
Brad Carlson:Well, no, actually a lot of them hog barns are located to be in close proximity to the crops where they want the manure to be used as fertilizer because so much of it's water. There's not good economics on hauling water around the road. A lot of them hog barns are just simply being located near where the crops are, where the manure needs to get applied, because a large percentage of it is immediately available as fertilizers, very valuable fertilizer product. Dairy manure, certainly valuable fertilizer, but it's just not going to be the same as applying hog manure.
Melissa Wilson:And that's why it's pretty critical to get hog manure injected or mixed into the soil as quickly as possible because of that high ammonia concentration. You want it to bind to the soil, not turn into a gas and be lost.
Brad Carlson:Yeah, exactly. And so if we look at some of the nutrient cycling, this is obviously the nitrogen cycle. We say this all the time, the nitrogen cycle is what it is. There's the processes, the conversions, the mineralization and nitrification and denitrification and all those things, is all the same. However, because of the complexity of the organic matter in manure, it is going to change the length of time, and therefore, how soon we can take credit for manure applications, depending on what that fractionation was.
Brad Carlson:And so, you know, kind of what have you found as far as, you know, we've started moving from swine manure to dairy manure to beef and poultry.
Melissa Wilson:So we actually are looking at, we have a timing application study right now. So we're looking at early fall before the soil is cool when the microbes are still active and making those conversions happen, And a late fall application when the soils have cooled down versus spring application versus if it's a liquid manure, a summer application too. And different species, we have swine manure, liquid dairy, solid beef manure and turkey. And we found that it's fairly consistent for the liquids. The spring application or at least the late fall application yield better when applied at the same rates than the early fall application.
Melissa Wilson:But with the solid manures, we've been seeing that the early and late fall are usually better than or the same as spring application. So that just goes to show that, you know, the ones that need to break down more to get the nitrogen, they're probably a safer bet to apply in the fall versus our liquid manures right now, some of our, the years that we've been having recently, it's been paying off to apply in the spring.
Brad Carlson:Right. And so if you think about kind of the area that I tend to focus a lot on, which is some of the water quality aspects, you know, the quote unquote bad things that happen with nitrogen, whether that's leaching or whether we're losing it through denitrification, that happens when the nitrogen turns into the nitrate form. So these organic molecules, that doesn't happen to these organic nitrogen molecules for the most part don't leach, they don't denitrify. In fact, I'm not even sure the extent to which they even break down when the soil is completely saturated. Think a lot of cases, it just kind of sits there in suspended animation.
Brad Carlson:You'd know better than I would as far as the anaerobic decomposition process of manure. But really, it gets down to how much time has there been for that manure to be on the ground to turn itself into nitrate? Obviously, you know, the whole, it all depends. It all depends on how warm it's been and how much time. And then of course, the loss processes of nitrogen are water based.
Brad Carlson:And so if it never really gets wet, then it doesn't really matter because it's not going to leach if it's not percolating through the soil, it's not going to denitrify if it's not completely saturated. You know, that's also part of this. But it does mean that the ones that have less organic nitrogen, more inorganic nitrogen are going to be much more susceptible loss, similar to the way that commercial fertilizer is. Well, let's talk a little bit about some of the other nutrients. I mean, we obviously tend to focus mostly on nitrogen.
Brad Carlson:We talk about phosphorus a fair amount because phosphorus is important with respect to crop nutrition. And from a water quality standpoint, phosphorus tends to be an issue because it leads to eutrophication or algae growth in water. Don't spend a lot of time talking about potassium oftentimes. Don't often spend a lot of time talking about micronutrients, you know, because we typically plan applications based on either nitrogen or phosphorus, but all that other stuff is there also.
Melissa Wilson:Yeah, I mean, for animals, what goes in must come out. So everything, if they're eating plants, then they have to be pooping out everything that plants are made of. Right? Right. So it depends on what you're feeding them too.
Melissa Wilson:Instance, poultry get a lot of calcium in their diet because they wanna make sure that they're making their eggs strong. So a lot of calcium also comes out of the back end of the bird as well. So there's little differences between the species. Like, typically, you're gonna find a lot more potassium coming out of hogs than for instance, dairy. And then if you're adding bedding and all that stuff, that's adding stuff to an organic matter.
Melissa Wilson:So yeah, it definitely changes based on how the manure is handled, what animal we're talking about, what they're fed, etcetera.
Brad Carlson:Well, then the other thing is, I think, you know, it kind of goes without saying, manure stinks. A lot of the stuff that stinks is actually sulfur bearing compounds. There's quite a bit of sulfur in there. And in general, we find that fields that have a history application typically don't need sulfur fertilizer.
Melissa Wilson:Yeah, that's pretty true. What's interesting about sulfur is that we can measure total sulfur in manure. We have a hard time analytically measuring sulfate, which is the plant available form. So that's one area of study that we're still working on is figuring out what does the actual availability of the sulfur look like. But you're right, in that long term historic applications, there's usually plenty.
Brad Carlson:Right. And, you know, and it really kind of matches where we're at with sulfur from a commercial nutrient standpoint too, in that we've kind of discovered that the soil test isn't very good. The test value really doesn't correlate very well to when we have a demand crop demand for sulfur. A lot of cases, you're much better able to plan sulfur applications just simply based on is there soil organic matter? How often have you applied sulfur?
Brad Carlson:And very particularly, is there a history of mineral application? Because a lot of that stuff that's had the history of mineral application just simply doesn't need it. Likewise, we don't typically look at needing to go very far with micronutrient applications on fields that have had manure applications.
Melissa Wilson:Yeah, I would say here in Minnesota, because you can overdo it too. Sure. But I haven't heard of that issue. I have heard of it down south in kind of that peanut production region. Had some specialists call up and ask if they're if we've had issues with copper or zinc.
Melissa Wilson:Yeah. And that's like in peanuts, they're very sensitive.
Brad Carlson:Okay, for having too much. Having too much. Too much, yes.
Melissa Wilson:Because in the manure field.
Brad Carlson:Right, right, right. Yeah, I mean, that's been an issue that's been raised. I'm not, again, I'm not sure that I've actually seen it in Minnesota, but we know that there's, you know, there's copper sulfate foot baths in a lot of our swine facilities where you have to step through that stuff and it, you know, it ends up getting tracked around. It ends up down in the manure pit and there ends up being fairly high copper content in some of that. Our glacial soils in Minnesota tend to be pretty well buffered against a lot of problems.
Brad Carlson:I think what a lot of people, if you're not a soil scientist, you've never studied soils, and I don't mean this to sound like, know, we're way smarter than you, that's not it. But what you probably don't realize, or if you maybe never spent a lot of time thinking about it is that the weathering process, that water and heat break things down. I mean, it's just things don't last when they're warm and moist. And so when you get into Southern climates where it's always warm and moist and it rarely freezes, soils also weather. So tend to be, soils tend to be a lot more benign and therefore whatever you put on them is what's there.
Brad Carlson:And so if something is kind of out of balance, if you will, it'll be out of balance. It's not going to go into the mixture, you know, and then be mitigated by all the stuff that's already there. So let's talk a little bit about what's kind of affecting nutrient content one way or another. There's a number of these things in general that affect this. So we've been talking about a lot of them, you know, particularly the animal species.
Brad Carlson:We spent a lot of time talking about the difference in that, you know, and then there's other things too, know, other aspects we also sort of mentioned, but kind of what are you finding for a range of variability based on some of these factors, Melissa?
Melissa Wilson:I would say it's hard to say specifically which factor is affecting what because they all are working kind of in parallel. But some of the things that we talk about are livestock housing and bedding. For instance, a lot of dairies have sand bedding and sand is pretty inert, so that's not adding nutrients. Right. But if they're switching to a different kind of bedding like-
Brad Carlson:Sawdust.
Melissa Wilson:Sawdust or in this like, in a lot of cases, we're seeing recycled manure. So, like, the solids contents being recycled back into our,
Brad Carlson:There used to be actually a lot of recycled shredded newspaper. Do we see that much anymore?
Melissa Wilson:No, I don't think we do see that that much anymore.
Brad Carlson:That was a thing thirty years ago. I remember when I was a county agent that our county's recycling center, I actually sold that as a product. They were bringing in newspaper and shredding it, and they actually had a John Deere baler that was bolted to the floor, and they would feed the paper through it, and they would turn out square bales of shredded newspaper, and guys would use that as livestock bedding.
Melissa Wilson:I can't remember. I think the reason I was told it just like it packs down too hard.
Brad Carlson:I can see that. I think it fell out of favor. I mean, but there were at least for a while, there were people using that.
Melissa Wilson:But yeah, the different ways that people bed their animals really affects things. I've heard a story. A farmer came up and talked to me afterwards. He used to have these old older watering systems where it was just kind of like a ball on the end of a pipe, and then animals would come up and push that in, and then they get their water. But like pigs are really playful, they'd like rub their backs on it.
Melissa Wilson:It would be dripping down all the time into the manure. He switched to those like the wet dry feeders. He said that he was able, he had been applying like six, seven thousand gallons acre. Once he got the new waterers, it ended up down to like 3,000. So it was like half just by changing the watering system.
Melissa Wilson:So that's a huge deal too.
Brad Carlson:Well, in addition to that, I mean, if you think about like the way beef cattle are handled, you know, if you think about out west where a lot of the feedlots, the beef feedlots, are just outdoors, you know, so now granted they don't get as much rain out there, but they're exposed to the wind and the rain and whatever. The further east you go, you start seeing these big high roofs, you know, that are because of more frequent rainfall, just, you know, it's better for the cattle to not have them in the rain constantly, but that has the effect then of keeping the rain off of the manure too.
Melissa Wilson:Yeah. And that's definitely a difference we see and hear about west to east too. And then out west, they worry more about like the salt content of manure because they don't have the rain to wash the salt out of the soil versus where we are, it's pretty darn rainy, and the salt issue usually isn't too big of a deal.
Brad Carlson:Yeah, and you know, as far as handling storage and handling systems, I primarily see that or think of that with respect to a lot of the old facilities. It feels like forty years ago, thirty years ago when I was starting my extension career, we were still kind of, I don't know if experimenting is the word, but there was a lot of differences in opinion on what the best systems were. You know, we were seeing a fair amount of outdoor storage, you know, we talked about that there was differences of opinion on what to use for bedding and so forth. Feels like, and I hate to use the term cookie cutter, but it feels like the systems have become a lot more standardized. I think it's become a lot more, people kind of know what works best.
Brad Carlson:And so we don't see a lot of variability anymore. And for instance, I think hog finishing barns, I mean, probably most other than a little difference in what they're being fed and a little difference in watering systems. Not a lot though. You know, most stuff that's been built in the last twenty years is all pretty similar to each other.
Melissa Wilson:Yeah. And I'd say that kind of changes based on the different animal species being raised too, right? Like hogs are pretty standardized at this point. I would say the beef and the dairy can vary a little bit more just because there's, you know, a lot older operations, there's a lot newer operations, so that does change a bit.
Brad Carlson:Yeah, it feels like there's a pretty wide variability too in terms of dairies as far as their size, you know, we don't see so much of the little ones anymore, the 30 cow, you know, but, you know, even you think about, you know, I guess it kind of depends on how somebody wants to define big, but I mean, there's 400 cow dairies, there's 1,400 cow dairies, and there's 12,000 cow dairies. And so there's gonna be big differences depending on those sizes and how they're handling their manure and how it's stored and when it's applied and so forth. And so, you know, that there's definitely, it's gonna be a lot more case by case basis and, you know, for a lot of those. I think we still do see quite a bit of on the beef side, just a lot of just smaller operations, people just with a few cattle. I mean, I mean, don't know, like I got two, you know, that's not very complicated there.
Brad Carlson:But even people that have like 20, it's not really so complicated.
Melissa Wilson:I think, too, the other thing that a lot of people don't realize is that the handling and storage actually impact the nutrient ratios pretty extensively. Like, you would think that an animal, if it's eating a plant, it would poop out the ratio, like nitrogen to phosphorus that plants need. But because of the way things are handled in storage and because nitrogen is so leaky in various ways, we actually derive that ratio down where it ends up being closer to two to one or something when most plants need five units of nitrogen to every one unit of phosphorus. So that's another thing that people don't really realize. And I wonder if that's one of the reasons for standardization too.
Melissa Wilson:In some cases, it just makes everything more consistent.
Brad Carlson:Yeah, and I think there probably is also a health factor of the animals too. I think like myself, I've got, you know, just a few pigs. We finish them in an outdoor lot, you know, depending, I mean, we've had issues sometimes with worms and then pigs being outdoors. They don't gain a lot of weight. They're eating as much as they do before, so clearly if they're not gaining weight, it's probably coming out the backside versus like the ones we got this year, I can't believe how fast they're growing, so pretty efficient there.
Brad Carlson:Definitely, there's going to be some differences in the manure on those things.
Melissa Wilson:Yeah, absolutely.
Brad Carlson:And so also, you know, we look at what they're getting fed. I think one of the big ones back, you know, I keep talking about back early in my career, but I guess that's what happens when you've been in for thirty years, is I remember in the mid-90s when there was a lot of issues with feedlots, there was a lot of concern over whether we had nutrients building up, but particularly the nutrient everybody was worried about building up was phosphorus because of its impact on water quality. You know, we aren't supplementing phosphorus in pig feed the way we used to. And so there certainly is a lot of difference as far as how livestock is fed and what ends up coming out the backside.
Melissa Wilson:Yeah, one of the big kind of advancements, I'd say, over the last ten, fifteen years now, I keep saying ten, but I think it's more like fifteen now, because I've also starting to be here for a little bit longer now. Been the phytase has been added to a lot of diets for particularly our monogastric species, our birds, pigs, etc. Phytate is a chemical basically form that holds phosphorus in plants. So to break it down, it's pretty complicated to break it down, you need this enzyme called phytase. The microbiome in cattle actually makes that.
Melissa Wilson:So like the bacteria, etcetera, in there just naturally make that. And we've figured out how to extract it from other things. I think they mostly extract it from like algae, from what I understand now. But then adding it to pig and poultry diets has made the animals more efficient at extracting the phosphorus, mostly because the phosphorus, like that enzyme, just helps them. So then once we figured that out, there was so much phosphorus coming out of the back end of the animals that they slowly started, cutting back the intake of the phosphorus because then they didn't have to pay for it.
Melissa Wilson:And, that that means that we're seeing a lot less phosphorus, particularly in poultry and swine than we used to.
Brad Carlson:Yeah, and I obviously, I'm a soil scientist, I don't have a background in animal nutrition. So particularly, I have not paid close attention to the price of livestock feed, but I do distinctly know and remember in 1995 that phytase was available, but most farmers said it didn't work economically, that they weren't going to use it, it was too expensive. They can supplement phosphorus in the diet way cheaper. Clearly those economics have changed.
Melissa Wilson:Yeah, I'd say, especially recently, everything is more expensive, right?
Brad Carlson:Yeah. And so kind of moving down this scale of what's affecting what that ratio is as far as the nutrients and the percentage of organic and inorganic. I'll talk a little bit more about the environment stuff. We've already mentioned that confinement versus it just being open is a big deal. We've talked about the differences in feeders and waters.
Brad Carlson:You know, one aspect that is probably going to cause some variability from one year to the next that we really can't control is what the weather is doing for us.
Melissa Wilson:Yeah. And that affects things in a couple of different ways. If it's outdoor storage, obviously more rain equals more water in your manure. But even in the barn, we've actually seen some significant differences, like in poultry barns. The more humid it is in a barn, particularly at the warmer temperatures, the more ammonia is in the air, and that's bad for the bird health.
Melissa Wilson:But it also means it's not in the manure anymore. So that's also not good. So the temperature and humidity really play a role in what's going on in the barn as well.
Brad Carlson:Yeah. And so I think, you know, it's one of the reasons why if you've got manure storage that's exposed to the elements or it's picking up rainwater, it's a good idea to be testing that probably annually. It's not necessarily an art per se, but in a lot of cases you're doing the application before you get the test results back. And so it is worth kind of noting what the weather has been like this year and adjusting your application rates based on past experience on whether it's likely that the nutrient content is going to be up or down kind of based on how hot or how wet it's been.
Melissa Wilson:Yeah, I think it's really important to keep track of the nutrient content. Some of these barns like the hog barns that are consistently fed, you know that there's not a lot of rain. Those you could probably get away with sampling every couple of years, but anytime you have anything changing, the feed, the bedding, you change the waters in your barn, whatever it might be, it's best to get that sampled. Or if you have outdoor storage and annual conditions might change things, try to sample annually if you can. And then keeping record and keeping note of patterns is always a good idea.
Brad Carlson:Yeah. And we talked a lot about the different kinds of bedding already. You know, you mentioned the use of separated solids in dairy bedding. What's that doing to the product that's end up getting put onto the field after it's gone through that process?
Melissa Wilson:In that case, we're seeing this in dairy barns in particular. I've heard some people using it in swine, but not. It's more common in dairy right now in Minnesota. And it is changing the nitrogen ratio a little bit in that there's a little bit higher ammonia content than the organic nitrogen. So, it's acting a little closer to swine manure once it's gone through that process.
Melissa Wilson:The solids is a bit of a different story. We haven't done a lot of research with that yet because a lot of it is going back into the barn, so it's not being land applied, but some is. So, we're hoping to kind of look into that soon.
Jack Wilcox:Thank you, Brad Carlson, Extension Educator, and Melissa Wilson, Extension Manure Nutrient Management Specialist, for all this information. We appreciate it.
Melissa Wilson:Thank you.
Brad Carlson: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.