UMN Extension Nutrient Management Podcast

University of Minnesota Nutrient Management Podcast Episode: “Nitrogen decision tools”
June 2023

Written transcripts are generated using a combination of speech recognition software and human transcribers, and may contain errors. Please check the corresponding audio before referencing content in print.

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Jack Wilcox:
Welcome back to the University of Minnesota Extension's Nutrient Management podcast. I'm your host, Jack Wilcox, communications generalist here with the U of M Extension. In this episode, we're talking about nitrogen decision tools. We have three panelists here with us today. Can you each give us a quick introduction?

Fabian Fernandez:
Hi, I am Fabian Fernandez. I'm a Nutrient Management Specialist at the University of Minnesota, located in the St. Paul Campus.

Jeff Vetsch:
Hi, this is Jeff Vetsch, Nutrient Management Researcher here at the Southern Research and Outreach Center.

Dan Kaiser:
This is Daniel Kaiser. I'm a Nutrient Management Specialist at the University of Minnesota Campus at St. Paul.

Jack Wilcox:
How much are we actually at risk of losing fall or spring applied nitrogen because soils are saturated in May?

Fabian Fernandez:
Well, Jack, that's an interesting question that comes up I think every spring. I've been here for 10 years now already in Minnesota and before that in other states in the Midwest, and that question is a typical one. It is a little bit difficult to answer sometimes specifically because it is so dependent on the conditions you are in.

Typically, the earlier applications have more potential for loss simply because you have more time for the transformation of that nitrogen that you apply that is mostly in some form that is ammonium or will transform to ammonium quickly for that transformation from the ammonium to the nitrate happening. And so, if it's already in the nitrate form, you have more potential for loss. So if you apply in the fall, of course that window of time is much larger. We didn't have a extremely cold winter this winter, and so I suspect that there was quite a bit of nitrogen that already nitrified by springtime.

The other, I guess, saving grace though for this year is that the spring, even though we didn't really have a really, really cold fall and early spring, it wasn't warm either. So it wasn't really warm, and so I suspect that the rate of nitrification was not huge either. But certainly some of that nitrogen was already in nitrate form.

Then the applications in the spring have to a little bit more with the nitrogen source. If you apply something that will transform quicker to nitrate like urea, for instance, urea, you apply urea, it transforms to ammonium in a few days typically. And then, depending on the conditions, you can start nitrifying it. Compared to, let's say, anhydrous ammonia where it takes a lot longer to transform to nitrate. And so, if you apply urea in the spring, chances of nitrification and potential for loss are greater than anhydrous ammonia.

The other thing that is interesting for this year is, of course, we are talking across Minnesota and we have pretty diverse conditions in Minnesota this spring. In some parts of the state, especially the southern part of the state, we got a lot more rain than some of the other parts of the state. We have areas where we have excess water and other areas where we are kind of in a drought condition already or getting there. And so, in those situations, again, it's the amount of water that drives nitrogen loss. If had you had a lot of water, there is more potential for loss.

And even with some of those big large rain events that we saw in South Central Minnesota where you got five to seven inches of rain over a very short period of time, my suspicion is that even though there is some risk of nitrogen loss in general, probably we did not lose as much nitrogen as we would expect. I think more often we lose more nitrogen when you get a wet spring where you get water rain every three or four days in small increments and that water just doesn't have enough time to evaporate. And so, you're basically accumulating water that starts then to trickle through the soil profile and moving nitrate down to dials.

In this year, the way that the rain came, I suspect that there was a little bit of, or quite a bit of water runoff on the surface. And so, there was no, I don't think, as much water moving through the soil profile. Even though we did see definitely tiles flowing more so than the last two years where we were in a very dry spring. But certainly not what we normally have seen in other years where the springs have been wet.

And so I think the biggest potential, I think for loss this year in those areas where we got a lot of rain is in the low laying areas of the field where water tends to accumulate and you end up with kind of a double problem in there. You get nitrogen loss mostly through denitrification because you have water saturated conditions in those fields or areas of the field. And then poor crop condition, which also impacts. You might have still quite a bit of nitrogen in there, but the crop is not really doing very well. And so, the potential for loss from those sites is also large.

Dan Kaiser:
Well, one of the things you've got to think about too is with denitrification, and we know that that's likely our main concern just with saturated soils is that, Fabian mentioned it, I mean, temperature is a main factor for that. So just looking at some data and some data we use from Nitrogen Smart, it's some older data, but it talks about soil saturated 4 or 10 days in the amount of the nitrogen denitrified from what was applied. So at soil temperatures at 50 degrees Fahrenheit, some of this earlier study was only showing 3% to 6%, whether you're 4 or 10 days saturated.

So since that's a microbial process, the cooler it is, I mean the nitrate can be there, but it may not necessarily be lost. So you look at a comparison at 77 degrees or close to 80 degrees Fahrenheit soil temperature. This study was showing at 4 days, 20% loss of what was applied.
That's in the nitrate form. Because that's key. It's got to be in the nitrate form. If your nitrogen's applied and it's still in the ammonium form, it's not going to be denitrified because the ammonium is fairly stable. And for 10 days, roughly 43%.

I think, Jeff, you had some research of some sidedress studies a number of years ago, it's probably been like 5, 6 years ago in central Minnesota where we had a lot of saturation in June, and there seemed to be situations then that almost all the nitrogen was seemingly lost. So that's kind of the main thing. It's always as a key of when this occurs. Because if it's early enough, if your fertilizer's not in a form that's going to be lost, I mean really the overall potential for that nutrient to still be there is relatively high. I mean, the main thing is where it's in the profile. Maybe it moved deeper in the profile and your roots are shallow, so you might see some early nutrient deficiency symptoms if the roots aren't in a place where it can be actively taken up.

Jeff Vetsch:
You're right, Dan. We had a study several years ago where we looked at using the PSNT soil test at V4 to V6 to try to identify fields that might have concerns about nitrate or losses through leaching or denitrification. We had a couple sites that had got a lot of rain in late May and early June, and by the time we soil sampled them, there really wasn't a lot of nitrate left in the profile in that top foot of that sample.

But at the same time, I totally agree with you, this situation is different because we had a relatively cool spring. Most of this rain came in the first 10 to 14 days of May, soil temperatures at 6 inches at that, here at Waseca at that time were only in the upper 50s and low 60s on average. So the biological activity of the denitrifying microorganisms as well as some of the end was probably still in the ammonium form and was probably not going to be as big a loss mechanism as it would've been if it would've occurred in late May or certainly in June.

Jack Wilcox:
What options do we have to assess nitrogen loss following heavy rain?

Dan Kaiser:
Well, as a soil scientist, I mean, it's kind of nice to always say that there is some sort of soil test option out there. I mean, right now the pre-sidedress nitrate test, I mean it's something that late May or early June is something that growers could consider. This is a one foot sample just to look at. It's more of a qualitative measure. So if you're above about 25, 26 part per million, you're probably okay, and that's of nitrate nitrogen. You might see some people focusing on tissue sampling. It's something I would avoid especially this early in the growing season. When you have saturated and flooded conditions, I mean if the plant's not taking up the nutrient, it's going to show up in the tissue sample even though it might still be in the soil.

So that's where right now, I think that's probably the best option. If you're kind of wondering where things are at, I would assume by now most of the nitrogen should be converted from ammonium over to nitrate. So anything that was applied maybe early May as warm as we've been should be converted that. So you should get a fairly accurate read on the amount of nitrate that's there. But the main thing I just want to stress right now is I think the soil test option is a better option than some other factors, particularly for corn. Because I think what you're going to see, particularly for tissue samples, you're just going to get a read on what the environmental conditions have thrown at that plant, and if things tend to improve, you might see the numbers start to go up. So it's one of the things that I'm really not crazy about it.

Now over Twitter, there was something that came across through our nutrient management account, a grower showing some plants that were over tile lines. They put in, I think last fall where they had some, it would look like red actually on the plants. And that's usually, a generally a visual symptom of oxygen deprivation or some other factor. It's not really a nutrient as much of an issue. That's kind of one of the things that we tend to run into with situations with a lot of saturation is the plants will kind of look weird and growers will kind of start looking at different nutrient deficiency symptoms to try to explain some of it when it could be true that it is a particular nutrient. But if that plant doesn't ... if that's oxygen starved near the roots, we know it's going to have some issues with taking up several nutrients. So a lot of things can occur.

So again, that's kind of where I stress right now. Really the soil test probably is your best option. It's not, I mean, a great option in terms of telling you how much nitrogen to apply based on that, but it's probably a good option if you're trying to figure out whether or not a field would need some supplemental and application.

Fabian Fernandez:
I agree with that, Dan, that really the best tool right now in these conditions would be the soil test for nitrate, and it should be pretty accurate right now as you mentioned because most of that nitrogen that we apply is already in the nitrate form and mineralization is taking place too. So that will give you a good idea of what is happening.

But the other thing that I also would like to mention is that along with that information, look at the state of the crop. Like I mentioned earlier, I suspect that this year we will have fields that will be kind of all over the place. There will be parts of the field where the crop will look great and other parts where it won't, and it has to do with this ponding that we had early on with some of those heavy rains.

And so, take that into consideration. Don't just look at the values and use that to decide, "Well, I need to apply more nitrogen if the end values are low in the soil." Because again, there could be a potential there that nitrogen might not be there, but the crop might not need that much nitrogen if it's not doing very well.

There were areas also where there was crusting in the field. You had some shallow roots in some of those fields. Then the crusting also creates some issues for oxygen to get into the soil and that that's important. The roots do need oxygen to take up nutrients. And so, if you have crusting, even though you might have a crop growing in there, that can also limit how much of that crop will be able to take advantage of what is in there, with nutrients, with water in the soil.

Dan Kaiser:
Well, I mean it was interesting kind of driving around Lamberton seeing rotary hose out this year. So it's the most I've actually seen them, growers trying to deal with some of these crusting issues in some of these ponded areas. The main thing as Fabian said though is you've got to assess and determine whether it's worth it. Because I've seen situations where, I mean, we get some of the saturation, it just sets yield back, but the amount of nitrogen it takes to maximize yield is the same in a good versus the bad area in some fields. I mean, you just really never know and that's kind of one of the issues with it. So throwing more nitrogen at it may not necessarily do anything. So it's one of the things that just that initial assessment of how that crop looks is really important right now just to figure out what's the best course of action moving forward.

Jack Wilcox:
If a grower is planning on applying nitrogen in season, what suggestions would you have for sources, timing, placement, and inhibitors?

Jeff Vetsch:
I would say ultimately the best application method for sidedress is getting it in the soil, especially with we've got these kind of hot dry soils at the surface now. So UAN stream injected or injected would probably be ideal. A lot of growers maybe don't want to go that route. Crop's getting too big, limited equipment or limited number of acres you can cover. So then, you look at maybe a high clearance sprayer and dribbling UAN, either between the rows or with a wide drop underneath the canopy. Certainly don't want to spray that on top.

If that's not an option or UAN isn't in source that you have, then maybe looking at urea broadcast over the surface. That could be done in a multiple ways, maybe with a spinner spreader, maybe with a high clearance tractor with a box on top. If that is done, that's probably where you need a urease inhibitor to limit the volatilization potential or volatilization losses of urea. Right now we got really warm soil temps. We don't have a lot of rain in the forecast. Maybe a chance for some today, maybe a chance for some this weekend. If you're going to broadcast urea and leave it on the soil surface, I think you got to have urease inhibitor in there to protect that from volatilization losses because we don't know when that next rain is going to occur.

Even with that urease inhibitor, I have seen little bit of leaf burning edges on times when urea laid out in this kind of heat. So don't be surprised if you see that. Don't think that, hey, that urease inhibitor didn't work. It's just that these are some pretty extreme tough conditions. The good news is I think the forecast is supposed to cool off a little bit here the next several days, but we got really warm soil temps. Fortunately they're dry, so that will be good. Moist warm soil is worst for volatilization losses. But those will be your top choices and their top options most likely.

Fabian Fernandez:
And one thing that I think is also important to remind people of is that at this time with these applications, you're not looking at the nitrification inhibitor. Don't waste your money in putting nitrification inhibitor because what you want is nitrogen to be available for the crop. I mean, ammonium and nitrate both are forms of nitrogen that the plant can use. The only reason to use a nitrification inhibitor is when you are concerned about the losses that we were talking earlier in the podcast when it's early in the spring and you don't want to lose nitrate. Right now, the chance of losing nitrogen because of heavy rains is pretty limited. The crops are starting to grow pretty quickly here. It's warm, and so there is a lot of evapotranspiration. So the chance of water, even if we get quite a bit of rain, the chance of that water making it into the tile lines or ponding there for very long is extremely low. And so, you don't need to put money into a nitrification inhibitor.

Then I guess it goes with without saying, but I will say it anyway, because it is important to be reminded that for nitrogen sources, and I agree with you Jeff, that the best thing to do is basically look at what you have at your disposal and that will create the least potential for volatilization loss or canopy damage. But one thing that sometimes people look at is slow release or control release products at this time of the year. I strongly recommend against those because again, the plants are ready to take up nitrogen now, so you don't want to be applying something that will be available four or six weeks from now.

Jeff Vetsch:
The other thing I would add and we didn't talk about is rate. In my experiences, and I open this up to Dan and Fabian too, is if these fields lost some N, it's not all the N. We don't need a large rate if you're going to go out there and touch up some of these fields. 30 to 50 pounds of N is more than enough to set these fields back into a condition where they can reach optimum yield potential.

Fabian Fernandez:
I agree with that, Jeff. It's kind of interesting, we are in this era where we want to be precise in everything to the last decimal of things. But in my experience, this very generalized approach of 30 to 50 pounds, it works pretty well year in and year out in these situations where you know you lost nitrogen. We try and we do a lot of research to try to figure out better how much we need to dial in for the application. But what I see in practical terms is that typically that 30 to 50 pound rate just about covers it in pretty much every situation if you need to apply additional nitrogen.

Dan Kaiser:
I don't know about you, but I guess with the situation now with the rain, I would kind of kill right now for a garden variety thunderstorm going along a frontline. I mean, this has been some goofy weather just with some of the rain and you'll get a little bit of rain and that's kind of a danger really with some of the products like urea, just a little bit of rain to dissolve it, because you get some of those processes going by which you get volatility. So I would just echo on what Jeff said is Agrotain or something similar, I would watch what product you're applying because there's some products out there that have the same active ingredient as Agrotain but not a lot. So you may not get as much effect of it. So it's one of the things to kind of ask some questions. If you are paying for it, if it's cheap, it may be an issue. It's cheap because it may not be quite as effective.

The other thing I would look at too, if you are dealing with continuous corn situations is look for sulfur deficiency too. So that might be one thing to kind of watch out for the spring because if you are sidedressing, ammonium sulfate isn't a bad option. It'll supply some of the nitrogen. You won't have the volatility and would give you a little bit of sulfur. I think if you're having a pre-planned of 20 to 25 pounds of sulfur, I don't think I'd worry about it too much. But if you're kind of in that 10 pound to maybe 15 pound range, if you're seeing some striping on the upper part of the canopy, especially if it's pretty pronounced, it might be something you want to consider.

That's one of the things I do see with sulfur in my research is that we do tend to see on some fields some striping early on, but it'll tend to go away once we get towards V10 as the soil starts to mineralize more. So it's I think just one thing to keep an eye out for, obviously seeing some yellowing, it might be just worth going out in the field just kind of looking at some of those areas and just seeing what the symptoms look like on the plant itself.

Fabian Fernandez:
There is one quick thing, this question about the placement. I don't know, to me, I feel like it makes absolutely no difference whether you apply nitrogen right next to the row or between the rows because nitrogen is so mobile that and it's taken up by mass flow that it doesn't really matter. But that is one thing that maybe we can just mention.

Jeff Vetsch:
Sure. So I think one of the things that we didn't talk a lot about is placement of these sidedress or in season applications. We have done some research with that looking at different placements. If you're looking at these more traditional sidedress application times where we're at right now in early June where we're looking at V4 to V6 corn, I don't think that there's much advantage or we did not find hardly any advantage to wide drops in our research. Any type of between the row placement, nitrogen's mobile, once it gets nitrified, the plants are going to find it. It's not going to be an issue.

Now if we get delayed and growers decide not to put on in and then they decide, "Hey, maybe I need a rescue treatment much later," and when I say much later I'm talking about these rescues that are occurring when the corns may be V12 or V14 or maybe almost up to tassel, then is there an advantage for wide drops? It's certainly possible because we know that the water funnels down the center of the plant, and it doesn't take a whole lot of moisture to get that activated if it's near the row. But ultimately, we've seen this the last couple years where we've gotten dry soil conditions and where the plant is taking up water is not at the surface of the soil. It's taking up water at one and a half feet or two feet. We can put all the N on and we can put it on with wide drops and put it right by the row, but we still may not get that in the plant and make grain out of it, especially at those later growth stages in rain-fed conditions.

And I know our scientists at the U of M who works on precision ag, they've had challenges with this the last couple of years. They're looking at using imagery to identify what's the right rate in season, and then they're not getting necessarily a great response to that in season, late, or mid-season nitrogen applications because it ends up being positionally unavailable or the plant may take it up, but it's not used to make grain and it doesn't usually give them a return on investment. That gets at the risk that Fabian talked about earlier.

Fabian Fernandez:
One thing that you mentioned, Jeff, that reminded me too is with the applications. I mean, another reason why applying nitrogen at this time of the year early June is probably the best if you're injecting the nitrogen, is because if you wait much longer than these, the roots are going to be reaching the center of the rows. And so, at that point you'll be doing a lot of root damage by applying nitrogen. And so, there's little sense in delaying the application much past around V6 or so, because at that point, again, the roots will be growing pretty much through the entire area of the field.

Dan Kaiser:
Well, it's one of the things too, I've been wondering, Jeff, maybe you could have some comments on this with wider ups. I mean, the technology really has put in double bands on both sides of the plant. I mean, really the question I have is whether or not we even need that with that. Because you see a lot of the data with just a single surface dribble band, since as Fabian said, the roots are reaching towards more towards the middle, is that a single band? I mean, at least as long as there's a band by each of the plants, I think that's just about as good a benefit as putting two bands on where now you've doubled the surface area.

If you're concerned about volatility of the 50% and in the UA, and that's the urea, that could potentially be an issue. So you see a lot of things, I mean they look good in theory, but I guess I'm a little more simple-minded when it comes to some of these things in terms of what's going on that simpler seals seems to be somewhat of the better options here in trying to stick with just some of the core knowledge we know in terms of timing in that versus trying to go too late and get real fancy with some of these applications.

Jeff Vetsch:
It's a good point, Dan. I think there's some old research, and it may have even been done by Mike Schmidt that said that even fertilizing every other row in a sidedress was just as good as fertilizing every row. I sometimes think engineering solutions to agronomic problems is, well, if one sidedress band on one side of the row is good, two must be better. I totally agree with you, Dan. I don't know that I know of the advantage of why you would need to wide drop on both sides, but I guess that's the way that's engineered and that's the way it's been designed. But I think growers could build their own or create their own and one would probably be adequate.

Jack Wilcox:
How late in the growing season can you apply nitrogen and what should you consider?

Fabian Fernandez:
Well, my thought on this after looking at data for a number of years with different timings of application is that the reason we do split applications or sidedress applications is either because we need to apply additional nitrogen or because we already planted that way and we apply only a small amount of nitrogen, and now we are adding the risk of nitrogen. But the main reason we apply nitrogen in season is if we plant it that way, is to minimize the risk of nitrogen loss. And so, as I mentioned earlier, at this point in the growing season, the potential for nitrogen loss is really low, so there is really no advantage of delaying the application. As long as nitrogen is in the profile, the plant will use it. The corn roots, they don't care if you apply nitrogen right before it was taken up or three weeks ago or five weeks ago. As long as it's there, the plant will use it.

And so, I hear this concept of spoon feeding the crop and it makes very little sense. I mean, it takes a lot of work, it takes a lot of field trips across the field, more expense, and it really doesn't do much for you. Because again, what you're trying to do with these in season applications is minimize the potential for loss. And so, I would say apply nitrogen and apply it now. As Jeff mentioned, if you look at the forecast, it's better to try to apply ahead of a rain event so that you get some of that nitrogen moving to the root zone, but apply it now. The crops are, I would say, across the state between V3, V6, somewhere in there, and so they're going to start taking up nitrogen very quickly and there is no sense in delaying that application.

One thing that some of the people that talk about spoon feeding the crop often don't talk about is the fact that you actually increase your risk for poor performance of that application the longer that you wait in the season because we tend to get drier and hotter in the season. And so, if you wait until the plant is like, I don't know, V10, V12 and you have to make it hard for yourself because you have now to use high clearance equipment and stuff like that, is that you could end up with pretty dry conditions and that nitrogen will just sit there on the soil surface and it will not be used by the crop. And so, you could have that really negative thing by just simply waiting later in the season. Like I said, we have done quite a bit of research looking at different types of application and the sweet wind of time to apply nitrogen in my experience is between V4 and V8. I would not wait any longer than V8 to apply nitrogen.

The other thing to consider, again, is the fact that the longer that you wait, if you're doing broadcast application, you increase the damage potential of that canopy. And so, that goes against you. As I mentioned, you probably need a specialized equipment, high clearance equipment and stuff like that, you get the application done the longer you wait. So there's really very little sense in waiting longer into the season to apply nitrogen at this point.

So go ahead, apply the nitrogen that you need now and don't delay. If you are in a situation where for whatever reason you do have to wait, I would not recommend going any farther than VT, when you get tassels showing up. That's the very latest that you would want to apply nitrogen. If you apply nitrogen after that point, it's not going to help you in any way in terms of improving yield.

Dan Kaiser:
I think normally with those late applications, once we get to a certain point, our soils are rich enough, they'll start mineralizing enough ends, so you start seeing your uptake tail off. That's one of the things that if you look at our recommendations, we do stress to try to, if you're doing a plan sidedress or even it's kind of a rescue treatment in this situation, to try to get done by about V6. And a lot of that just so to give you more of a ability to catch a rain to get that nitrogen down to the roots. So that's kind of the main thing. If you're planning for it, just make sure that you're setting yourself up that the nitrogen will be where it needs to be because if it's just laying on the surface, it's not really going to be doing any good.

So looking at Southern Minnesota, it seems like the rain's been more consistent there, so you may be able to catch a rainfall event. Central Minnesota and some of those other areas, I'd be a little bit more concerned, and some areas where the rainfall hasn't showed up. So the earlier, the better, just to make that decision. I don't think I'd wait too long, if you're going to make the decision to do it.

And we've seen that if you look at a lot of the ag press out there talking about late season applications, VT and above, and these are planned splits, and we just do not see the benefit to it here. I think there's maybe one year out of the last 10 or 15 that there may have been some evidence of something post VT as a rescue treatment increasing yield, but that's pretty rare. So again, the situation, I mean, I would just be doing some assessments now, trying to figure out what your options are. Then hopefully just with some of those tools, we can help you make a decision in terms of what's the best thing to do. Because it's really, we're kind of at the point where I think you'd be want to be making these decisions if you're looking at some sort of in-season application in terms of what you need to do.

Jack Wilcox:
Are there any last words from the group?

Jeff Vetsch:
One thing that I would say is that I think the fields that are at the greatest risk, Fabian touched on this earlier, is that fall application especially early applications of swine manure that were done in the earlier fall or late late summer of last year. And then we still have a lot of fall urea that goes out here in south-central Minnesota and these areas that have seen a lot of rain, especially in back in that period or that window back in early to mid-May. Those are the two things in particular where I would be concerned. I think the later anhydrous with an inhibitor and the spring applications, I'm not all that concerned about these fields. Of course, rate is a factor too. If growers are putting on a rate that's significantly greater than what we are recommending at the U of M, even if they did lose some end, they probably still have adequate end in those fields.

Dan Kaiser:
Well, and Jeff, you brought up fall urea too. I think the thing to watch out for this year with that is since we didn't really have a whole lot of frozen soil over the winter, it would be in a good winter for volatility for anything that was shallow incorporated. So I just would keep an eye on those fields and then maybe do an assessment now. I mean, even in spite of some of this rainfall, just with the winter we had, we may have seen some more volatility that we do tend to see with some of those applications. Because that's one of the things that volatility doesn't stop even in the winter with fall urea. I think it's one of the loss pathways we underestimate with that. So it might be a good, just check on some of these fields. Right now it's the window where it's optimal to make some of these decisions. So just to do that sooner than later instead of waiting too late and are risking some reduction in yield.

Fabian Fernandez:
Jeff, thanks for bringing that point up about fall urea. In my previous comments when I was talking about how much risk we have of loss, I was not even thinking about urea because as far as I'm concerned, that's the worst thing you can do. I mean, if you apply fall urea, you're basically setting yourself up to pay for urea or for nitrogen twice. To pay in the fall and then pay again in the spring because even if you have really good conditions, you're going to lose nitrogen. I mean, we have seen that in research year after year consistently. Even with years where we have low potential for nitrogen loss, you do lose more nitrogen with urea in the fall than you would with a spring application. So you end up having to apply more. So definitely check those fields and from now on, don't apply fall urea. It's just not a viable alternative.

Then one more thing that I just wanted to mention, for the late applications, as I mentioned, I don't recommend it. But in some situation, if you really need to apply nitrogen and it's close to tassel, that time, the only place where we've seen benefits of those really late applications is when the corn is severely deficient. If you're looking at the crop and it looks about normal, the chance of getting any benefit are slim to none. The only situation where we've seen that benefit again is when you see that the crop definitely is nitrogen deficient. And so, adding some nitrogen will definitely give a bump in the yield that you we would get otherwise.

But if that's not the case, don't worry about it because, and again, looking through research, at this time of the year from now, basically to harvest, even though we apply nitrogen, the majority of the nitrogen that the plant is taking up is through mineralization. It's through the process of mineralization. It's the nitrogen that is mineralized in the field, and so you will get most of that from that source and you would from an application.

Jack Wilcox:
All right. That about does it for this episode of the Nutrient Management Podcast. We'd like to thank the Agricultural Fertilizer Research and Education Council or AFREC for supporting the podcast. Thank you for listening.

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