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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.
Advancing Nitrogen Smart, from the University of Minnesota Nutrient Management Podcast:
“Carryover nitrogen: A potential credit for N fertilizer reduction in Minnesota”
June 5, 2024
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.
(Music)
Jack Wilcox:
Welcome back to episode 3 in our special series “Advancing Nitrogen Smart”, from University of Minnesota Extension. I’m Jack Wilcox, University of Minnesota Extension communications. Today we’re talking about carryover nitrogen with Extension educator Brad Carlson and Extension nutrient management specialist Dan Kaiser.
Brad, there's been a lot of conversation about the concept of carryover nitrogen this year. Explain what carryover nitrogen is and why it's important to be aware of.
Brad Carlson:
Well, Jack, it's not really a concept that we have dwelt on a lot over the long term. The reason for that is, nitrogen is prone to be lost to the environment. It naturally converts to nitrate and then it's lost through water-based processes, whether either there's drainage through the soil profile or the soil is saturated, is lost into the air, so any nitrogen that's present, say following last year's crop, if it was unused fertilizer or if it was left over from mineralized sources from last fall, last summer, the data has shown that on an annual basis, that's usually lost before the crop gets up and growing next year, so it's not something we normally look at at assessing. That being said though, there always is some, I guess, what we would call background level of nitrogen present in the soil. However, because our rate recommendations are based on actual rate trials, that's reflected in those rate trials, whatever is there is part of what made up the yield and the nitrogen response in those fields.
There's no reason to try and calculate that or figure out what it is, is just reflected in what the results are. Now the key to that is, that's kind of under average or typical conditions, so the question becomes, if the conditions aren't average or typical, then what should you do? As I said before, the loss of nitrogen is water-based, and so if it's really wet, it's possible maybe we lost more than normal, meaning we might need higher rates of nitrogen than normal. If it's really dry, that's likely that it all just stayed in place, and so we would look at having a nitrogen credit. The last three years have been exceptionally dry, and so we've talked about this now for three years in a row that there could possibly be a nitrogen credit in place.
Dan Kaiser:
Brad, I think that it's key what you talked about, with our current rate recommendations is that there is a certain amount of assumed background nitrate values. We know that our soils will mineralize so much and they tend to maintain so much, and a lot of it is coming through mineralization towards the end of the growing season that's occurring even though the crop's not actively taking up the nitrate. When we talk about carryover nitrogen, really, is the key here is, amount that exceeds that natural background level with that. We will talk about this, I think, going forward, what conditions there might be, but certainly you look at 2021, 2022 and 2023 being dry years, we know that there potentially is some greater carryover just because the crop may have not effectively utilized it.
Brad Carlson:
Right, and while we don't spend a lot of time dwelling about what the water holding capacity is in the soil profile, most of our soils are probably going to hold seven, eight inches of water. If we look at the fact that the loss processes of nitrogen are water-based, that starts when the soil becomes saturated. When it's really dry, first we've got to get enough precipitation to saturate the soil, then the excess starts coming in, either ponding it or in terms of moving it through the drain tile and leaching it.
These last few years, now last year was a little odd because it did get really wet at the start of the growing season, and now this year, again, we're kind of dealing with a situation where we've started to get adequate precipitation. There's actually some parts of the state that have had some excess precip, so we're kind of back there again, however, we've barely just got back to field capacity in most places, we haven't probably seen a lot of loss, and so even though we're kind of at that starting point, that base level of total saturation, the odds that we lost a lot of last year's crop probably aren't real high.
Dan Kaiser:
I think one thing to kind of go back and make clear is that if we look at a soil test for nitrogen, you can have both ammonium and nitrate analyzed. Our soils will maintain a certain level of ammonium, those levels tend to be higher when you've had a recent applied fertilizer because obviously we're applying the majority of our fertilizer, it's going into that ammonium form other than UAN, which has some nitrate, that you can measure both, but when we're talking about residual, really we're focusing mostly on nitrate, because again, our soils since we tend to nitrify quickly, is that the bulk of the nitrogen we have that the crops are utilizing are in the nitrate form, so it's really the main thing if you are taking a soil sample just to know that carryover nitrogen that a lot of times we're focusing on nitrate itself.
Brad Carlson:
Yeah, and the other element of this, of course, is that if we do have a lot of extra nitrogen in the soil profile and then we go ahead and apply a full rate of nitrogen, A, we are buying fertilizer that we didn't necessarily need, but then in addition to that, because it may be in excess of the crop needs, we may be flushing it to the environment, and so if you look historically at years where we've had a drought, then following that when it finally gets wet again, we've seen nitrate numbers in the Minnesota River spike, and so that represents that we kind of end up flushing that out of the system. In an era when we are very concerned, the society as a whole is very concerned about the amount of nitrate in water, as an industry, we need to do a better job of accounting for how much nitrogen is still left in our soil and actually using it by the crop instead of just going out and applying a full rate of fertilizer again and then taking the chance of losing it.
One of the data sets that we look at, in addition to looking at the amount of nitrogen loss, in addition to the amount of nitrate in the river is also, if we look at our drainage plots, particularly, we've got those drainage plots at Wasika, we've got some at Lamberton. What we've seen throughout the 2000s and the 2010s is, on average we see nitrogen losses when we're following best management practices of roughly about 10 pounds of nitrogen per acre, even if we don't apply any fertilizer. That kind of represents that loss of that background or last year's nitrogen prior to this year's crop getting up and growing. If we follow best management practices, those numbers go up to about 15 pounds per acre, or roughly about two thirds of what we're losing is natural not related to the fertilizer. However, we've got a data set that goes back from the years 1990 to 1993 from Lamberton, Dr. Giles Randall did that research, and that was coming out of the drought to the 1980s.
At that point, we really weren't adjusting our nitrogen rates lower, following some of those catastrophic failures we had in some of those years. We actually saw, in those cases, we saw nitrogen loss numbers that were closer to about 50 pounds per acre. We do actually have data that substantiates this. We've kind of looked at this now, the last couple of years that has been dry, some of our friends in the industry have been supplying us with soil testing data, and so it is possible to do soil testing and credit for this if we need to.
Dan Kaiser:
One of the things to remember when it comes to loss is that when we start talking about our recommended rates, as Brad said, when we look at applying the optimal rate, we know that while there is a small increase for every pound of end we applied in terms of the potential for loss up to the point which we reach the optimal rate, it's when we exceed that when it becomes a problem. That's when this talk of carryover nitrogen, I mean if that nitrogen is indeed available, essentially it's just additional fertilizer that's out there in the field in excess of what you applied. That's one of the questions when it comes to carryover, and some of the things I know Brad that you've looked at with some of the numbers that have been provided from some of the soil testing labs.
Brad Carlson:
Yeah, if we take a look at what some of those numbers are, courtesy of Minnesota Valley testing labs has given us some of the summary data. We of course don't have individuals soil test results. In Minnesota, we have had recommendations for a pre-plant nitrate test primarily in situations where it's corn on corn following a drought. Okay, so that's looking at basically unused fertilizer from last year, and in situations where there's a long-term manure history, and then again, particularly in drought, and really the kind of working in here is the fact that if there's something left over from last year's corn crop when we're rotating to soybeans, well, we don't apply nitrogen to soybeans anyway now. I had a farmer friend of mine ask this winter and said, well, should I be looking at this and changing to corn on corn?
Well, if you're listening to this podcast, it's way too late for that, you've already made those decisions. However, it probably was something at least to look for if you did think you had a significant amount of nitrogen left in the soil profile. This research that went into this, I was actually a grad student pulling... I shouldn't say a grad student. I was an undergraduate, as an intern, I was pulling some of these soil samples that went into these recommendations at the time, and kind of what they discovered was, there was enough noise in the data that they decided to go stepwise. Since the soil test is really only testing for nitrate, kind of where they start is six parts per million, so anything at six and below is considered to be kind of what that background level is, so we don't credit that stuff.
These things gradate all the way up to 18 parts per million based on the credit. Now, that credit at 18 parts per million is 155 pounds of nitrogen per acre. Back when this came in place, that was kind of where our highest application recommendation was. Now, we're in a situation where at the 0.1 price ratio, corn on corn, we may be looking as high as 195 pounds of nitrogen. Dan, you extrapolated the data and kind of ran the line out from where it was up to 24 parts per million soil test and looked at that as probably being a 205 pound nitrogen credit. What we saw in and '21 and '22 was 28, 23%, roughly about a fourth of the samples that went into MVTL in the fall that year had that 155 pound credit. However, this past year, that spiked up to 46% or almost half of the samples that were submitted.
If we look at that last category where we have that 200 pound nitrogen credit, it was 30%. I mean, it was one third of the samples that went in. It had a 200 pound nitrogen credit present based on that spring soil nitrate test. That's pretty significant. Its worth noting, those aren't random samples. Those are people that sampled, because they thought there could be a credit and they were looking for it. You go looking for something, you very well might find it. That was kind of the case here, but it does kind of indicate what some of the potential of that was.
Dan Kaiser:
I'm kind of curious too on how many of these numbers actually get used because that's one of the things that we don't really know right now. I mean, how many growers are effectively utilizing the data to reduce their rates? If they aren't, one of the big questions I have is why? I mean, is it just that overall fear that they're not accurate? I mean, looking at some of the data we have, and I did this in southeastern Minnesota where we don't typically recommend a fall test. I had a site where the grower had manure, had cover crops, and the fall sample came back over 24 part per million.
I know, just for a fact, since we had nitrogen rate trials in that field that were non-responsive, that number is probably accurate with that, so it's one of the situations, is trying to figure out what is the issue here and why we wouldn't want to use some of this data because we do know there's some significant risk. Again, if we get situations where we get a lot of tile flow, that if it's there, it's going to flush out. I mean, that's one of the really major issues.
Brad Carlson:
Dan, I actually had a conversation with somebody from a soil testing lab here not very long ago, and that was the exact point that he was making was, so few farmers are doing this pre-plant soil nitrate test primarily because they don't feel comfortable making the credits, so why bother going through the effort and getting the numbers?
Dan Kaiser:
Some of what I look at this test is, and we'll talk more about it, the nice thing about it is it's a proactive test. You look at things like they might be using for their equip dollars, like the basal stock test, this is essentially a report card at the end of the season. I mean, I'm looking at what happened and there's nothing I can change at that point. I mean, I would rather see growers, if this was an option for them, to look at this because I do have questions on the lower end with credits right now. I mean, it's one of the things we're looking at.
Say you're in one of those lower categories, 10 PPM or less, how accurate that data is. I mean, that's one thing I don't know right now, but looking at it, I mean even for the southeast, I mean taking a fall test and trying to find some of those fields that you might be 24 per million or higher, I think there's some value in there because you might just be able to get away with maybe a small starter rate in spring and just apply that and then find some other way to reassess in season. That's some things we'll talk about here in a moment.
Brad Carlson:
Right, if we look at the protocol for the test that we recommend, it's based on a 24-inch soil sample, because nitrate is mobile and it will move through the soil profile, you can't just take the top. It may be there and it may be deeper in the soil profile, and so really the kicker on all this is that the recommendations are calibrated based on 24 inches, so even if you say, well, I don't want to do that, I'll just look at the top foot. Well, the recommendations are based on two feet, and realize that potentially your number would actually drop if you added that second foot, and therefore you may be over crediting if you don't take that deep of a test.
Dan Kaiser:
It might drop or it might go up, you don't know. I mean, it just depends on where the nitrate is, and that's one of the things that every once in a while I'll have a grower ask me, they have six-inch samples where they run nitrate in the validity of that particular test, I mean really I can't tell them a whole lot because again, it's based on a two-foot sample. In most cases, consultants or retailers that are doing these samples, what they're taking is a zero to six, then they'll take a separate six to 24-inch sample and run that for nitrate only, so you'd be looking at your top, six inches for most of your PK lime maybe you're looking at some of your DTP or metals, but you do that split so you have that profile down to two feet.
Now, one of the key things on this nitrate test is, this is in situations where we would expect residual nitrate, so if you're dealing with just a traditional corn, soybean rotation, no manure in the system, it would be a situation where I just really wouldn't expect a potential for a residual nitrate. If you're following the soybean anyway, I mean soybean is a nitrogen utilizer. It's going to utilize the residual that's there. If you're not supplying it, you don't let it compound by having that additional nitrogen on top of what's already there. I mean, it's one of the things that we do have in the recommendations, is a nice flow chart that talks about situations with crops. If you're following alfalfa, it's not probably a go od test, because the alfalfa as it's mineralizing, there's not going to be nitrate there, so it's not going to be accurate.
If you're following soybean manured situations, it would be a good opportunity to incorporate that in. If you're following corn, again, manured situations or situations like '21, '22, '23 where you have continuous corn, maybe not all the nitrogen you applied was utilized, there might be some potential for residual nitrate remaining in the fall, so it isn't something that you can use across all acres. I mean, certainly you can take it just to see. I mean, maybe if you've got cover crops in there, it might be something you want to take, if you have corn following soybean, but in general, it's really focusing on those situations where residual nitrate might be present.
Brad Carlson:
Right. Dan, I think that some of these really high numbers that we're seeing this year are the result of the fact we've had three dry years in a row. Normally, we don't recommend taking it. Obviously, when you're growing soybeans next year, who cares? But in the case where you've got three years in a row, I mean we're back around to where two years ago we may have had some leftover from a corn crop and now it's been dry ever since and it's still there. Some of this might have been building up for multiple years. There's really nothing wrong with taking the test. It is going to be accurate, it's just a matter of whether you're likely to see anything. It's extra effort and it's extra expense in situations where you probably wouldn't find anything, however, there's nothing wrong with doing it.
Dan Kaiser:
No, and the question always is timing fall versus spring, I mean long we've kind of held that. I mean, in some labs like AgVice would recommend going in after wheat, after it comes off the field and sampling early in the fall. I mean, realize the fact that numbers will change. I mean, we know that from research that you're not going to get the exact same number if you sample in fall versus the spring.
For South Central and Southeast, I mean Spring is probably better, but even if it does change, if you're looking at situations where you're 24 part per million plus, it's probably not going to change that much, and you're still in a situation where you could credit a lot of it. In that case, if you're looking for these situations where you might have these really high nitrogen credits, I mean, I think fall, it's just not the ideal option, but it's good, at least you've got a number to go by. That's what I think key, is having a number to go by that I can make a decision before I apply nitrogen to the field because once it's there you can't take it out, the crop has to take it out. It's a thing that being proactive to me is better than being just full on reactive and trying to make corrections all the time in season.
Brad Carlson:
Well, and really I think the point to keep in mind is, that number is accurate at the time it was tested. It's just a question of whether it's still accurate at the time the crop is up and eating nitrogen next year, and so from that standpoint, if you credit a nitrogen and it was extraordinarily wet in between the time you took the sample, and then say early June, you can maybe figure that some of that nitrogen was then lost and you maybe need to come back and add a little bit more with a side dress application.
The other aspect of this, we talk about this sort of general rule of thumb, that nitrate will move roughly about six inches deep for every inch of drainage. When we've got capacity in the soil to hold six inches of precipitation, first, when we've got that deficit fumbling a drought, first you got to get that six inches and get it to saturation, then you got to get all that drainage. The odds of it actually getting lost out the bottom in some of these dry years really isn't actually very high, and so in some of these circumstances, I think it's okay to go ahead and take that test and then just kind of keep an eye on what the conditions are like since then.
Dan Kaiser:
One thing that you will notice if you do take this test is that labs are going to report the data in pounds per acre. What they typically do with the two-foot test is, they take a part per million, which is what the result comes back from the lab, and they multiply it by eight. If you do get it in pounds per acre, if you want to look at some of our recommendations, because we don't recommend crediting down to the pound, that direct conversion from PPM to pounds per acre. There are some crops, if you look at it, that will recommend just in the rate equations like wheat, sugar, beet, I think is different, they've got a table kind of similar to what corn does, that we don't recommend down to the pound.
Just realize the fact that that's what's happening, the labs are converting it. Looking at your crops, I mean, if you're growing more than corn, if you're trying to use that number, there might be a different way in terms of what that number is used. In other state recommendations, I mean, I kind of like the fact that recommendations are local, but soils do go across state lines, so we wouldn't recommend it, but I mean it might be good just for comparison, if you have a recommendation that you want to look at, Minnesota versus neighboring states if you're on the border.
Brad Carlson:
Yeah, the problem with that, Dan, is just simply whether they use different sampling protocol to develop their recommendations. If they're saying, use a one-foot sample, and ours was a two-foot sample and you took a two-foot sample, and then they may not compare anymore. You do have to be careful about that.
Dan Kaiser:
One thing I do want to make it clear is, we do not recommend this test after fertilizer application. I'll get questions every once in a while that growers will take samples to try to figure out how much of their nitrogen is remaining in the spring from fall applications using ammonium numbers, and we have no way to interpret those values. I know Fabian Fernandez has been looking at just total inorganic nitrogen, which would incorporate the ammonium and the nitrate, but there's really no way to utilize that right now, so if you are looking at this test, essentially you need to be doing it before the fertilizer is applied. I mean, manure and yeah, I'd still like to have it beforehand, but the ammonia value, since that ammonia is going to be there and it's going to convert to nitrate, it hasn't done it at that point, we just really have no idea what that number is. Looking at it, just focus on nitrate, ammonium really is really not the key, and just make sure you take that sample before your fertilizer is applied.
Brad Carlson:
Right, and similarly with manure, we will get that question of like, well, I made a manure application, yeah, I had a manure test, but it was a year old and we applied whatever rate, and I want to see how much nitrogen is out there, let's go take a soil test. Not calibrated for that. It only is testing nitrate. Particularly with dairy manure, a lot of that is in an organic form, you're not going to pick it up at all, and so this is not a test you can use for that purpose. Similarly, when we're talking like, say, a second year credit for manure, again, a lot of that is organic and it needs to get mineralized into ammonium and then to nitrate. It's not going to pick that up, so it's not usable for that purpose.
Dan mentioned the sugar beet test. Again, it's worth noting that the sugar beet test in Minnesota is in pounds per acre, and it's for four feet deep. So you do need to be kind of careful if you send the sample in, what you're asking for and what kind of results you get back. So just be mindful of that.
As far as our credits are concerned, we talked about that already. We mentioned the fact ... Dan mentioned the fact that he's pretty comfortable with some of those high numbers, maybe not so much on the low numbers. But that table is available at our nutrient management website that you can find on the internet. Tables don't go so well on podcasts, so I'm not going to go through with reading those.
Probably the kicker for the beet test part, though, is if you do get that test back in pounds per acre, what John Lamb, our retired soil fertility specialist, told me was use about 60% of that number credit, as far as the pounds per acre that it recommends.
Dan Kaiser:
That's for corn.
Brad Carlson:
Right. Correct.
Dan Kaiser:
I mean, if we're trying to convert from the beet recs to corn-
Brad Carlson:
Right. That is correct. Now, as opposed to that, there's the pre-sidedress nitrate test, which is taken during the growing season. I don't know, some farmers get kind of confused between the PPNT and PSNT. We tend to rattle those terms off. But the PSNT is a sidedress nitrate test. That would be taken during the growing season. Typically, the way this technology has been suggested to be used in the past is you would apply some base rate, low rate of fertilizer, and then come back and see how much more you need to finish the crop off. So it's potentially a way to do variable rate fertilizer or to just simply lower your rates based on what's going on in the growing season, and so forth.
This particular technology's been researched multiple times at the University of Minnesota, going back to the early '90s. And then Jeff Vetsch and Ryan Miller and I did a project here about a decade ago, and it's being worked on again. In the past, we've really had a hard time with calibrating those numbers to recommendations and coming up with a good correlation for those. I think the key is from a big picture standpoint, if you're going to use that, we still look at a two-foot sample, kind of the same protocol. However, that may be changing. I guess we'll see about that, but that's what we've tried in the past.
Dan Kaiser:
Yeah. You got to remember, I mean, this is ... A lot of this work was developed in Iowa, if you look at the pre-sidedress nitrate tests, where a lot of the information comes from. Because Alfred Blackmer, who did a lot of work down there, he was a nitrogen specialist at one point in time, they were looking at a one-foot test. You're looking at collecting the sample in early June, by about the time the ... You want to get it before the plants get about knee-high. And then to interpret the test, I mean, really, the challenge is if we look at all of our data, it's what I call a qualitative test. It's really good at telling me if I have enough. But if I have too little or below that point, really not as good telling me how much I should be applying. There are even situations where we can get numbers that are below that, that were still at adequate yield at the end of the season.
I mean, what the recommendation is ... For now, if you look at the Iowa data, what they recommend is every PPM below 26 PPM, they recommend seven pounds N. That's one of the things we're looking at now. Because Fabian Fernandez was looking at that critical level, he's seeing actually it might be closer to 20. I'm looking at this test, if you're 20 plus or 26 plus, I mean, I have some confidence or a lot of confidence, when it comes down to it, that you should have enough nitrogen to carry you through. That's one of the things, that even if we stick with a one-foot test on this ... I mean, it's kind of one of the things I'm wondering, if this is a good complement to the PPNT, is that I can flag some of these fields that have high levels early on, maybe apply a base rate, then come back in and reassess while it's still a point in time where I can apply nitrogen. I'm wondering if that would give growers more confidence in that system to use those PPNT numbers.
Brad Carlson:
Sure.
Dan Kaiser:
That's one of the things, I think they do complement each other well, it's just getting a good handle on that, what we call that critical level. At that point in which yield is maximized. That's really the big thing, right now, we're looking at, and then looking at some of these numbers for that rate recommendation. Because that's really where there's a lot of interpretation involved, where it's not an exact science. Because you get below the critical level, there's a lot of questions in terms of what you should do.
Brad Carlson:
Part of the problem with this test, and this is kind of what we ran into when we did that study about a decade ago, we were going in and geo referencing. We were using a handheld GPS unit and we were marking where the soil samples were coming from. We were actually sampling twice. So we were going at V2 and V6. That was only roughly about eight days apart. The corn grows really fast that time of year. We were finding soil nitrate numbers that varied any way from 180% to 18%. So anywhere from it could have doubled, and it might only be one fifth of what it was eight days ago. That's incredible inconsistency.
Now, what we think the problem is, is that ... because this was a corn on corn site, there's a lot of residue out there. We know that the breakdown of residue will actually pull nitrogen out of the soil. It's a process called immobilization. It doesn't mean it's gone or not there. However, it's not nitrate and it's not being picked up by the test. There is still this issue if we take an in-season test and there is some interference, some immobilization interference because of decomposition of residue, it does make the interpretation of the results difficult.
The other thing that we ran into is the fact that the nitrogen cycle happens everywhere. It'll happen in a plastic bag also. So you do need to be kind of careful with handling these samples. When we're in season, it's been suggested that they be tested wet. In our particular trial, we were handling these samples ... We were splitting them in half. We were drying half of them and sending them to a conventional lab for a dry nitrate analysis. The other half were being done wet. Some of the fields, they came up really nice on a one-to-one line. And then other ones, they kind of fell apart. What we discovered was that the ones where they weren't tracking, they weren't coming back with the same numbers. In some cases, those soils were sealed in Ziploc bags and they were allowed to get warm. We ended up with denitrification of nitrogen in the Ziploc bag. So it also brings home that if you're doing these kinds of tests, the nitrogen cycle will happen. Be careful with how you're handling your samples.
Dan Kaiser:
I think moving forward with this, I mean, really, the thing that I like to think about on this is, I mean, this is a tool that we could potentially use. You think about it in years. We look at 2024 where you have not very strong commodity prices, but still, nitrogen prices are relatively high, what it would mean if you could cut back significantly in some of these fields and reduce some of your application. Really, the key here is, I mean, this ... looking at tools, is we don't have many tools looking at variable rate nitrogen. I think this might be one of them, if we could come up with a better set of guidelines. I mean, I think we have good, but I'd like to be able to establish that some of these things will work.
Because, I mean, some of the other options that are out there, I mean, it just doesn't really work so well, particularly if we look at aerial imaging. We look at other types of management where it just doesn't seemingly help us predict in terms of what the overall rate we might be needing on a recommended basis. That's really where I look at a lot of these things is trying to get a good handle on some things, that I can be proactive in my management instead of constantly being reactive.
Some things, if you look at it ... One of the things I will say with soil sampling is it is really important to do a good job because I think the adage "garbage in, garbage out" is pretty apt here, is that if you just go out and just haphazardly take a sample, it's really not going to give you very good data. Now, do I have a general guidance on how many samples you should be taking? Say you want to take the pre-plant nitrate test. Not really. I mean, I think it'll depend on your field.
One thing about nitrate is that you can see a lot of just small scale variability. But I think on a larger scale, I mean, we've done some testing in some fields, that five, 10 acre areas that we've had have been pretty consistent. I think zone sampling might work very well for a situation like this, but it does take some planning. It's one of the things that if you are going to do it, just do a good job. Because I think that's kind of the main thing with it is I see a lot of times people just go out just without a plan. Really, having a plan is really the best thing you can do to make some ... just make the most out of the time you're spending and the money you're spending on these types of things.
Brad Carlson:
Well, we're going to cover variable rate nitrogen in a lot of detail in a future podcast, but I think probably the last point, and it's really worth noting with this, is these are technologies intended to allow you to cut back on fertilizer. When you cut back on fertilizer, you're not going to increase your yield. The idea here though is that it's adequate amount of plant nutrition and you will maintain your yield. That's what we're looking at. But do realize that your yield's not going to go up when you apply less nitrogen.
I guess maybe the take home on this is if you're going to do this, if you're going to take the time to do it and the expense to do it, follow the recommendations. Otherwise, it's just money spent that you didn't need to spend a lot of effort on. That's kind of the last philosophical part of this. If you're not comfortable with it, maybe just try it on a small area. Cut a field in half and try it there. See what you think. Maybe not on your whole farm. I think it's time we need to get going with some of these technologies that we have that allow us to reduce application rates in places where research is indicating we can do that.
Jack Wilcox:
Extension educator Brad Carlson and Extension nutrient management specialist Dan Kaiser thank you both very much.
Brad
Hey thanks again.
Dan
Thank you.
Jack Wilcox:
If you have questions for either Brad or Dan, please email us at nutmgmt@umn.edu. Thank you for listening and we look forward to seeing you next time.
Advancing Nitrogen Smart is proud to be supported by the farm families of Minnesota and their corn check-off investment through Minnesota Corn.
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