How soil conditions & chemistry affect nitrogen loss
Hello and welcome back to Advancing Nitrogen Smart, the special podcast series from University of Minnesota Extension. I'm Jack Wilcox in Extension Communications.
Jack Wilcox:On today's episode, we'll explain some of the major ways that nitrogen is lost in the field. Here with me as always are Daniel Kaiser, nutrient management specialist with Extension, and then Brad Carlson, Extension educator.
Jack Wilcox:Brad, what are some of nitrogen's major loss pathways, and how do they begin to take place?
Brad Carlson:The first thing we wanna talk about here is denitrification. Now in general, when we talk, you know, we've talked a lot in the past about the loss of nitrogen being water driven, and the two pathways for that are leaching and denitrification. That requires the nitrogen to be in the nitrate form. And so, you know, we're already gonna we're kinda gonna kind of assume that, that we've got nitrate out there. We're not gonna talk about that.
Brad Carlson:We've talked about that stuff in the past, with the nitrogen cycle. But, when when we have, nitrate present and then the soil becomes completely saturated, what happens is microbes in the soil, with no oxygen present start looking at nitrate as a place to get oxygen from. And so these microbes in the soil, will convert the nitrogen eventually back into n two gas. If the conversion is not complete, that can end up as NOx, which is considered a greenhouse gas. And and, you know, that that's another problem on a topic probably for another day.
Brad Carlson:We don't really have a lot of good, solid information looking at the fractionation of the gases that are produced from denitrification. But, but if the process goes complete, it turns into into gas, which is the primary component of the atmosphere. It's what we're breathing into our lungs right now, and so we really don't consider that to be a major problem or a major contaminant. You know, it's worth it's worth noting, and, again, it's a topic we've talked about a lot in the past, that because it's microbial in nature, it does require the cells to be warm. We don't see a lot of denitrification happening in the fall and and, the early spring and through the throughout the winter because all those microbes just can't get going, when it's that cold.
Brad Carlson:We don't see a lot of that activity. It's really in, in the early summer or if we think about in in, for instance, 2024 when it was so extraordinarily wet in June, that's where we have some really major problems with denitrification. When the soil is saturated, when when it rains enough that we've reached holding capacity of the soil for water and then it starts ponding up or at least it's saturated to the point it can't hold anymore, That's when this process kicks in. Because the microbes take a little while to get going, it doesn't really start right away. It's not instantaneous.
Brad Carlson:So if we get a big thunderstorm and it rains two inches, you know, you're not losing nitrogen, you know, yet that evening. It's really about one to two days after the soil saturated that the microbes get ramped up and get going. So if the water runs off or if it drains away quickly, we're not gonna see a lot of that. It's really when it ponds up and just stays wet for a long time, that that that really gets going. You know, and the other thing that's important to realize is that that the bacteria require a carbon source, and so all that happens when it's close to the soil surface that some of the nitrogen that may have been moved deeper in the profile, kind of below the topsoil when the soil starts getting light colored, we don't see a lot of denitrification from that part of the soil profile.
Daniel Kaiser:So we'll have a discussion. I think you're talking a little bit about soil temps because I think that's the main thing that we'll get some questions here and there on is, when we get a lot of early season water logging that, you know, there's some concern always about nitrogen loss. And with denitrification, we know that while we can be, you know, saturated in the spring for extended periods of time, but the soils are cool, it's probably not gonna be as big of an issue. The, you know, the big thing about denitrification, Brad said, you know, talked about that one to two days of water logging, and we know that, you know, there there's always gonna be some loss of nitrogen due to denitrification on a yearly basis. You know, you've got areas of your soil that, you know, might be a little bit more saturated than others that things that we can kinda call microsite denitrification where there'll be some loss.
Daniel Kaiser:It's just these these large events are really where we get a lot of concern about, you know, particularly in situations where the soils are warm enough where we can get a lot of, a lot of denitrification to occur. And, you know, whether it's good or bad, you know, we do know that their denitrification does pose a significant loss potential in some soils. I mean, you look at Central Minnesota, you know, Western Minnesota, Northwest Minnesota areas where we have a lot of clay, those are the areas that are gonna be more prone to potential risk of loss. When we start talking about denitrification, it it is a way that when you look at several of the methods to try to reduce the amount of nitrate in water that's that's being looked at. And it's really the, you know, way, if you look at, bioreactors and a few other things that, trying to take advantage of some of this.
Daniel Kaiser:I mean, the main thing, though, is trying to get it all the way back to n two, so full, you know, full conversion and and not get NOx somewhere in the profile. So, I mean, there are some positives of it if you're looking at it from the drainage aspect because, you know, getting it out of the water, this is really the way that we're looking at doing that.
Brad Carlson:Right. And and, you know, I guess it's sort of using the nitrogen cycle. I don't know if I wanna say against itself, but, just taking advantage to how nitrogen behaves in the environment for the purpose of trying to keep it out of the water. And so, you know, while we certainly don't wanna see denitrification happening in our fields where the crop needs the nitrogen, once it's out of the field, denitrification is something that we can harness to try and get the nitrogen out of the water. And so, you'll see denitrification, of course, in some of these, what we call edge field practices or conservation drainage practices.
Brad Carlson:It's going on, for instance, in bioreactors. You'll see some of that happening in saturated buffers, although some of that also is is just simply nitrogen use by perennial plants growing in those areas. But we also see it happening in in constructed wetlands. If you can detain the water for long enough in some of these high organic wetland type situations. We can see it turn back into into gas.
Brad Carlson:And so it is possible to actually harness this, you know, the this phenomena, I guess, if you will, in order to kinda mitigate or clean up the water too. So, you know, it's it's it's a process in general. We don't want it out in the fields, but but it is something that we can we can actually make some beneficial use of also. So if we look at rates of denitrification and the implication of soil temperature, you know, we've already mentioned a lot that, it doesn't happen, to a great extent when the soil temperature is cold. If we look at the 50 degree temp, which, of course, is a a key temperature with respect to nitrogen application, we don't want any fall anhydrous going on until the soil temp gets below 50 degrees.
Brad Carlson:There's some classic data out there that looks at the rates of loss and from denitrification. And so at 50 degrees, if the soil stays saturated for four days, we're only looking at, like, 3% loss. And, if it's ten days, it's 6%. So we're not talking huge amounts. Now, you know, the thing you have to remember, though, of course, is if frost goes on late February and it's saturated for most of March, you know, that can really add up and, you know, then we can end up lose still losing a fair amount that way.
Brad Carlson:However, again, you know, we typically don't see a lot, in that respect. It's really when the soil temperature gets to be, high, like, seven you know, 77 degrees, close to 80 degrees. You know? Now if we're saturated for four days, you can lose about 20% of your nitrogen. If it's saturated for ten days, it's 43%.
Brad Carlson:You know? It's getting close to almost half of it. And so, you know, in that way, when we get saturated in June, if we're thinking about doing rescue treatments, we can start kinda getting a feel for, you know, how much n we thought we wanted for a total in rate and then start figuring what's, what's 20% or what's a quarter of it, what's a half of it. You know, do we need to come back and do a rescue treatment?
Daniel Kaiser:So the big thing here, you know, as Brad was talking about, I mean, temperature is a big component of this. And while, you know, we've got some data looking at this, it can vary from field to field. So the main thing is when you look at where we're at most risk for loss, really, you look here in Minnesota late May into June, really is that time frame that we're more concerned in the years we've seen some pretty substantial loss due to denitrification have been years where we've had, some extended periods of of soil saturation within the June. Now the issue with when we get to saturated soils, if we get a lot of ponding is, you know, do you have anything left after essentially the water goes away and, you know, whether and that's kind of the decision then as how much did we lose, and that's all kinda really difficult to predict on that. But, one of the things that we know is, you know, denitrification is a pretty significant pathway to loss, especially when we're seeing more rainfall occur across the state.
Daniel Kaiser:There's there's significantly more risk in many of these soils. So it's it's it's something to watch out for, you know, again, with, you know, higher clay soils that this is a pathway. I think people always think that leaching is gonna be kind of one of the major issues, which it can be, but we know that, the downward movement of nitrate isn't as fast in some of these high clay soils. So, know, just something to watch out for, and it it's the main fact here is you have to have nitrate present, and that's always the thing when we start talking to growers when they're worried about loss pathways. It's just kinda working through some of the the nitrogen cycle.
Daniel Kaiser:And, you know, if we're in that ammonium form, that's really if the fertilizer's there, we we don't have the same issue. So it's only if there's nitrate present in the soil itself.
Brad Carlson:Right, Dan. And that's one of the reasons why we we really only typically wanna see anhydrous ammonia put on in the fall because the other forms of nitrogen, they they turn into nitrate too fast. And therefore, you know, we talk about or I just mentioned, you know, what if it stays wet the whole month of March? Well, if all your nitrogen is still ammonium, you don't have to worry about it because ammonium doesn't go through denitrification. It's nitrate that does.
Brad Carlson:And so, you know, that that's another way to try and, you know, make the nitrogen cycle work in our advantage is is kind of understand these processes and, use them to your best advantage. So the the loss of denitrification of nitrogen ends up in the atmosphere. Let's just keep going and talk about other ways that nitrogen is lost to the atmosphere. Volatilization, is is another process that, you know, particularly, I think a lot of us think about anhydrous ammonia. You drive by where there's an application going on.
Brad Carlson:You can smell ammonia out in the field. You know, we like to think or hope that that's never really that significant, but, but it can be, you know, particularly if you have, really wet soils, we can oftentimes see the slot not sealing when the applicator is going across the field. Every so often, we will see, soils that are so dry, you know, that that is possible. I know a few years ago, we had a situation where the soil probably was in decent shape. However, it froze lightly at the surface, maybe one to two inches deep, and there was some commercial application that went on that was sort of slabbing or chunking off the frozen topsoil, and that was also leaving some exposure for where the anhydrous was being applied.
Brad Carlson:So, that can be a problem. You know, hopefully, from year to year, it's it's not, it's not real huge.
Daniel Kaiser:So let's just talk a little bit about, you know, what factors increase volatility. And we know that if you start looking at fertilizers themselves that liquid, fertilizers are really gonna be more subject of initial loss due to volatility than solid fertilizers, and that's, you know, mainly because in a solid form, where we need water most of the time for a lot of these reactions to occur. Broadcast surface applications, you know, those we know that losses can be reduced immediately with incorporation or, you know, if you're banding has subsurface band, we we know that's not gonna be as much of a risk or watering in with irrigation. And with a, you know, product like urea, which is is pretty subject to volatility, generally, quarter inch of rainfall, a quarter inch of water. There's been some data I've seen where, you know, maybe it takes a little bit more than that to get it effectively incorporated.
Daniel Kaiser:But, I mean, really, the the thing is to get it off the soil surface. Surface applications, particularly in situations where you have a lot of residue, is really a big problem, and that is because of how urea converts. I'll talk about that here in a little bit. You know, just we start talking about incorporation, trying to get in the urea incorporated to a depth of, you know, at least two, three, four inches is really important to try to stave off some of this. Moist soil surface where you get a lot of water evaporation, you know, this is kind of an issue because with urea specifically, if you place it on the soil surface, it doesn't take a lot of water to start dissolving that material.
Daniel Kaiser:And the thing about urea is when you can see it, it's less of an issue when you can't see it. And that's mainly because when you start looking at the breakdown of urea, you know, again, it has to be in the liquid phase. And if it's near the soil surface, if the surface is wet and you have just the right conditions where water might be evaporating from the surface, you're likely gonna see a lot of volatility of the of the ammonia, the n h n h three versus the ammonium. And I guess that's one thing I should mention is when we talk about things, ammonia gas, that's n h three or three hydrogens, that's a gas. Ammonium is an ion that can be held in the soil, that's n h four.
Daniel Kaiser:So there's an additional hydrogen that's picked up by the n h three in the soil that will stabilize it as n h four. So that's kind of a a big thing in in in why we start talking about application, trying to get the stuff incorporated in the soil so it has that ability to go from ammonia the gas to the the ammonium form. High soil temperatures, I mean, that kind of just aids in the evaporation process. I mean, that's kind of a big big issue. And then high soil pH.
Daniel Kaiser:If you look at the dynamics or the chemistry of ammonia in the soil, there's always a ratio of ammonia n h three to n h four, and that will shift based on pH. You're never getting to get to a situation where if you say apply a product, you're gonna get more n h three. Eventually, most of it should end up as n h four or the ammonium or the ion that's held in the soil, but that does tend to shift. Do you start to see, a higher, you know, percentage of just more, ammonia that that percentage increasing is not necessarily higher than the n h four as pH increases. So that's one of the things to kinda consider with.
Daniel Kaiser:Urea is, it's probably more critical to look at incorporation, with some of the higher pH soils, you know, more more close to the time of of application. How soon for incorporation? You know, generally, a cup I mean, you know, two to four days is when we start seeing things start to ramp up. So there is a little bit of a window that so things that can be immediately incorporated.
Brad Carlson:And you're talking a lot about, urea, Dan. I think it's also worth noting that volatilization is a major loss process when we do manure applications. We're not spending a lot of time talking about manure here today, but if you look at the charts on the percentage of nitrogen available based on the application method, you know, that's almost strictly driven off of volatilization and how much nitrogen is gonna just blow away in the wind. If you do a surface application of liquid manure and don't get that incorporated in a timely fashion, you can use an lose a awful lot of the nitrogen that way. And so that's also an important factor, to realize that, you know, that that's really the the the kicker there with why we either want that manure applied subsurface or we want some kind of almost immediate incorporation is to prevent this process from happening.
Brad Carlson:You know, again, it will speed up when it's, warm and windy, you know, maybe not huge amounts. But, you know, as as always, when things are kinda cool and and overcast, we don't see the kind of, extreme pressure that we'll see often in other times.
Daniel Kaiser:So, you know, when we start talking about volatility, how do we prevent that? And really, the the main way is we do have some products out there that are called urease inhibitors. And, you know, what this is, if you look at urea, urea essentially is an organic nitrogen source. I mean, you know, some people don't think about it since it's commercial fertilizer, but it is organic. It's got carbon actually in it.
Daniel Kaiser:It's, when you look at it, there's an enzyme urease, which is in every soil. It's actually in plant tissue and higher concentrations in the soil. So that's where if you're dealing with, urea applications, if you apply it, say, in a continuous corn situation where you've got a lot of residue, with, you know, reduced tillage or, you know, just any situation where there's a lot of residue on the surface, you're gonna see a little bit quicker, conversion of urea into some of these intermediaries in, you know, potentially affecting your risk for for volatility. So that's kind of the main thing. You know?
Daniel Kaiser:So what ends up happening is urea, the urease will essentially split the urea into ammonia and then carbamic acid. That's kind of an intermediary. And then eventually, what you end up with is for every molecule of urea is, two molecules of, ammonia gas, n h three, plus carbon dioxide. So it's kinda what it'll tend to split into. And that ammonia initial step where it converts is the problem because if that's near the soil surface, you got a lot of evaporation that's going to volatilize off to the atmosphere.
Daniel Kaiser:That's kinda where incorporation comes into play. If that's deeper in the soil, if there's water, there's some acidity or hydrogen ions, that can bind with that n h three to form n h four, then you can stabilize it and you prevent some of the loss. So the inhibitors, what they do essentially is they slow the activity. Essentially, they block they they kinda block it the that urease from effectively working, they slow down the process so you don't get just an immediate flush of, hydrolysis is what this process is called, after the the urea is applied. So, you know, that they we do know they are very effective.
Daniel Kaiser:The main thing, if you look at, you know, some of the products that are out there, NBPT, which is, the if you look at Agurtain, that's the primary active ingredient in, that inhibitor. It's also now off patent, so there's a lot of generics out there. A couple other products, Duramide, which is Anvol, which is, you know, sort of kind of, ABPT adjacent. And then, Lemus is another product that has been out there that there's some some data showing some impact of these products on delaying or slowing urea hydrolysis. I mean, it's not perfect.
Daniel Kaiser:I mean, it might give you you know, it might stretch out where you start really slowing the release or the slowing the hydrolysis process to more of a, like, a two week window. But, eventually, it's going to wear off, and you're gonna get all that hydrolysis to occur. So that's just giving you more essentially, for some of that incorporation if you're waiting for rainfall or you've got tillage for that, that to occur. And these things are really most effective, really with surface applications, of urea, and you can incorporate it. That's really the thing you have to think about, if you're you're banding or you're, so you're applying urea with strip till or you're incorporating, within four days to the depth of two to three inches, really, these products aren't gonna help you all that The main thing on these is just to make sure, one, if it is like an NBPT generic that the product has good activity and has high enough concentration because there's some products out there that have a very, very low concentration of NBPT.
Daniel Kaiser:And while they may, you know, have some effect, they're not gonna have the desired impact you're gonna want compared to some of these other products. And then there's some other products out there that just they they claim to have the similar activity, but they just don't necessarily work. If a product is, slightly acidic, and if you apply it, say, in a band with urea, you can have some effect. This is kinda what happens with ammonium thiosulfate. With UAN is you can have some slowing impact, where the acidity of the produced by the thiosulfate can impact the loss of your or some of that ammonia from that, that band if you're putting it with, 28 or 32%, but it's not gonna have anything like you're gonna see with some of these these these urease inhibitors.
Daniel Kaiser:So the main thing on the inhibitors, just know that it I would just look into it. If you're going to your retailer and, you know, just buying something, it's kinda always nice to know that the money you're spending actually is on something that will do the desired effect.
Brad Carlson:Alright. So that was loss up to the atmosphere. Let's talk about the nitrogen going down. The primary loss process this way is leaching, and and we've talked a lot about in the past that that clay particles in the soil are negatively charged.
Brad Carlson:Nitrate molecule is also negatively charged. Therefore, they don't stick together like, you know, the the poles on a magnet, positive, negative stick together. The two negatives, they don't stick together. And so nitrate is just free in the soil. And and so, know, some people will call it being dissolved in the water.
Brad Carlson:It's really technically not dissolved in the water. It's really that it's just free in the soil, and when the water moves, the nitrate's free to move on with it. And, you know, we've talked a lot in the past about why that's important. And I think everybody, if you're listening to this podcast, I'm pretty sure that you're well aware of, what the issues are with nitrates in water. And so, obviously, this is a big problem, and we've been focusing an awful lot on just simply trying to keep the nitrate out of the water.
Brad Carlson:So, when we look at the, you know, the the problems relative to surface water, for instance, the the nutrient reduction strategy that most of the states in the Upper Midwest, including Minnesota have, we've got these targets for the the reduction in the amount of nitrate load going into the Mississippi River. So it's important also to remember that, that's a factor of the nitrate concentration in the water times the total amount of water that's that's flowing, and and that that'll give you the total amount of n overall that's going through the water. And so, you know, we focus a lot on the nitrate concentration in the water, of course, and meeting drinking water standards or surface water quality standards. Overall, though, we're also going to have to be sort of, accountable in dealing with the total amount of nitrogen, which has the factor of how much it rains, which is almost completely out of our control. But, that's that's an important factor, in this loss process.
Brad Carlson:So farmers will frequently ask, how fast does it move? Where's my nitrogen at in my soil? Did I lose it? And we don't have a perfect answer for that, but then the general rule of thumb, and this kinda comes from you know, Jeff Vetch supplied me with the number initially. But if we look at a lot of the data from the research plots at Waseca done on the drainage study there, we can kinda see this matching up.
Brad Carlson:And and so we would say for an inch of drainage, so that's like an acre inch or imagine your farmland having one inch of water on top of it, one inch of water being lost through the drain tile. That inch of drainage moving through the soil profile is gonna move nitrate about five to six inches in the soil profile. So, again, it's not dissolved. It's not just simply moving completely with the water. It's just moving along at at a pace.
Brad Carlson:And and so the soil texture is important here. So when we have sandy soils, the irrigated areas, those kinds of places where we have coarse textured soils, we can move the the nitrate actually more like a foot for every inch of drainage that we have. So that's important if we think about the fact that tiles typically about three feet deep. You know, it'll take, you know, roughly speaking, you're talking about five to six inches of water drainage in order to move significant amounts of nitrogen down into the drain tile. However, if it's sandy, you're only looking at about three inches.
Brad Carlson:Well, that's pretty common to get three inches. If we look at the overall annual water budget, you know, in general, we might move eight inches through the system during the entire year, but only a portion of that, and in fact, a very small portion of that is during the growing season because of the amount of water that the corn's taking up. However, if you look at the irrigated and the sandy stuff, it's it's pretty normal to see, you know, as much as, three inches of drainage through that stuff, and that's why we, recommend splitting the nitrogen up so that you're just simply not losing it that way. So as far as trying to deal with that as a problem and and mitigate it or prevent it, you know, there's some very simple stuff. You know, a lot of it gets back to our recommended practices or the four r's, if you will.
Brad Carlson:But, you know, the the the number one thing that we've talked a lot about over the years is just flat out don't apply nitrogen you don't need. You know? Keep your rates in line with what the crop actually needs. Don't put on insurance nitrogen that's more than what you need, you know, kind of adapt to conditions. And if you're applying higher rates of and have a reason for or have some justification for it, that's likely that the crops are gonna use it, not just simply that, you know, you want it for insurance or, you know, worst case is like, oh, I know I'm gonna lose a lot into the water, so I'll put more on.
Brad Carlson:Well, let's try and keep it out of the water, you know, if that's the strategy. Apply closer to when the plants need the nitrogen. That's really the theory that applies for sidedress nitrogen, so we don't really see a great crop response for sidedress. You know, we've said many times in the past that crops don't respond to this, you know, spoon feeding method that they really could care less when the nitrogen is applied. There's no such thing as it being fresh.
Brad Carlson:It's either there or it's not there. The real advantage to side dressing is that you're not subject to loss. If it's not out there, you can't lose it. And so if we simply, you know, delay the timing of the fertilizer application to when the crops need it, it's not out there subject to those environmental factors that can cause loss. There are products on the market, nitrification inhibitors.
Brad Carlson:You know, as we've said already that it's gotta be in the nitrate form in order to leach it or to lose it. If you keep it out of the nitrate form, just like the volatilization losses or or the denitrification losses, I guess, I should say, you know, you're not gonna lose it in that way. And so nitrification inhibitors can be a tool to help us with that. You know, another way to deal with it is to try and arrest it in place. So that's the strategy we use with with cover crops, is is the thought that maybe this is gonna take some of that nitrogen back up out of the soil, and it's not present to be lost.
Brad Carlson:And the last thing is we've talked about, you know, I mentioned that we're looking at a total reduction of the amount of nitrogen running down the river, and it's being a factor of the concentration and the amount of water running through. If there are methods to reduce the amount of water running through the tile, you know, that's also potentially a method that can be effective, such as controlled drainage where we're manipulating the water table and, only draining the water that's necessary for crop production and therefore reducing the total nitrogen load going out through the drain tile. So like I said, you know, we can sort of keep track of this on an annual basis as far as whether we're losing nitrogen. If you kinda keep track of the the water budget, you know, you can kinda feel for, when we're saturated in the spring and things start drying out and and how much, how much rain is falling from the sky, or you can kinda monitor your drain tile. A lot of our drainage systems are designed for half inch drainage coefficient.
Brad Carlson:So meaning if they're running at full capacity, they'll move about a half an inch, in a day, or takes two days to get rid of an inch of rain. You start feeling for how much water is running through that drain tile and where that might have moved the nitrate to. It's frequently an issue where we'll see the crops a little bit yellow, and you think, oh, we're nitrogen deficient. But in reality, we just moved deeper in the profile. You get a couple sunny days.
Brad Carlson:The corn starts to grow. The roots go deeper, finds the nitrogen, everything greens back up again. But, it is a process that it is possible to keep track of, and it's it's also one of those areas that potentially, crop models might be able to do a better job of keeping track of in the future and helping to alert us, when we're likely to have lost a fair amount of nitrogen. If you look at the overall loss and the seasonality of it, you know, there's some data from Waseca that Giles Randall put together looking at the total amount of precipitation. This study was roughly about twenty years ago now.
Brad Carlson:However, it's again, it's really only kind of, it's only qualitative in nature anyway, so we don't need to worry about, the specifics. But at that point in time, we were getting more rain as the summer went on. There was, you know, on average going back, that far, there was actually more rain in August than there was in July and and June and so forth. So we saw increasing rainfall amounts as the summer went along. However, we saw the amount of water being discharged by the drain tile decreasing significantly as the corn started to grow.
Brad Carlson:And so, you know, particularly by the time we get to July, August, and September with the full fully functioning big plant deep root system, you know, we see that drainage, backing off as far as they're not being so much. And so that water uses is just simply reducing the amount of nitrate ending up in the tile, as well as, of course, corn's picking up that nitrogen and using it as a fertilizer source that it was intended for. But that leads to the seasonality where a lot of our nitrate loss is actually coming prior to the the, growing season. We see significant amounts of it in April and May, when it's, you know, it's really not possible to have been this year's applied fertilizer. It was that stuff left over from last year or residual nitrate for mineralization post growing season the year before.
Brad Carlson:And and then we see nitrogen losses, really going down quite a lot, once the corn gets fairly tall.
Daniel Kaiser:So one of the main things, you know, talking about just kinda wrapping some of this up is, you know, there's also some loss runoff and erosion. You know, we do know there's a a small amount. I mean, most of that's as total nitrogen. The amount of nitrate actually in I mean, there might be some, but it's not gonna be you know, there's a lot of that's gonna be total nitrogen that's gonna be a part of the organic matter that's being lost through runoff and erosion. You know, crop harvest is another way.
Daniel Kaiser:Yeah. It's not necessarily a bad loss pathway because we can't really bank nitrogen in the soil. So, you know, essentially, what we're trying to do is get as much as we can to you best utilization we can. So, I mean, crop harvest isn't that bad. I mean, we we know that there's a large amount of nitrogen.
Daniel Kaiser:We don't base our recommendations on that removal just because, just it isn't a a predictive factor on that. And I guess the glass, I mean, you know, few other things, ammonia fixation. We know that, you know, some of the ammonia that's there that can be fixed with the clays. We there's not a lot of data on that to to talk about. But, you know, looking at it, you know, these some of these things, well, they are lost pathways.
Daniel Kaiser:I mean, harvest is really the kind of thing that's more of a positive than anything else. We're just trying to stabilize what's nitrogen is there in our exported product.
Brad Carlson:Yeah. You know, the term that keeps getting bantered about, not really by farmers, but you'll see it in the press so often, is runoff of fertilizer and pesticides. That's just become this generic catchall of all of the evils that are out there. You know, primarily, I think those of us involved in agriculture realize that runoff of fertilizer most frequently is pertaining to phosphorus. It's not really a big thing with nitrogen.
Brad Carlson:We look at if if you just do some rough calculations based on rates of soil erosion, you know, under just normal circumstances and and organic matter, how much nitrogen is in the organic matter, you know, that would come to be about 10 tons per acre per year of nitrogen being lost that way. Some actual data that was measured in Nebraska had a more, like, less than seven. And it's worth noting that the atmospheric deposition of nitrogen in which frequently is coming from wind blown, soil particles, similar to the the what's washing out the surface, That can be on the general range of about 10 pounds per year. You know? So roughly speaking, we're kinda zeroing out what we run off, versus what's being, kind of deposited by wind and rain.
Brad Carlson:So these are just not major processes when it comes to nitrogen. But, you know, I think it's important that farmers understand that. So when you hear somebody throw that term out, you know, engage them in a positive conversation about it. Say, hey. You know, actually, that's really not a thing that's, that's that's going on here.
Daniel Kaiser:I mean, just in addition to that, Brad, though, mean, it is a problem if you apply fertilizer, say frozen ground, and it's sloping ground that, you know, runoff of fertilizer then could be an issue. I mean, normally, what you're talking about are what's actually already in the soil. So it is something to watch out for because remember, all fertilizers are water soluble. So if there's the rain comes, you've got sloping ground, it's on the soil surface or it's frozen ground where the water that you might get can't penetrate into the soil, then it's more kind of an issue, but it's it's not of the nutrients that are are there. It's stuff that you've applied.
Daniel Kaiser:I mean, really, those are pretty easily avoidable things, in terms of a timing aspect, or an incorporation aspect to get around. So, you know, we don't really if you you talk about what's already in the soil, I mean, it's it's not really gonna be as much of an impact as it would be in terms of freshly applied fertilizer.
Jack Wilcox:That was Daniel Kaiser, extension nutrient management specialist, and Brad Carlson, extension educator.
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.
