What to expect after heavy June rains
And welcome everyone. Before we get started today, I wanna introduce and introducing our guests, just going over a few quick webinar tips for any new attendees who might have here for our strategic farming field notes program. Basically, we're here to answer any questions you haven't have a discussion. Today will be about the basically, all the excess rain we've been having. And we'll use that q and a box to type questions.
Anthony Hanson:You can click and enter that. That's the bottom toolbar on your Zoom screen. Use the chat function only if you're having technical issues. We'll save that for that versus if you have questions, use that, q and a option instead there. You can just hold your mouse near that bottom.
Anthony Hanson:That should show up there if you aren't seeing it. And the other thing is when you log off today, we'll have a quick survey. Just lets us know how we're doing and, things that, you know, we can look forward to in the future here. This session is being recorded and it's gonna be posted to your favorite streaming service for podcasts later this morning. So for folks who can't attend today or for future sessions, you can always find these just on your podcast services.
Anthony Hanson:So again, thank you for attending Strategic Farming Field Notes. Today, we're gonna talking about basically, you know, all the rain we've had in June, what to expect after that, especially for the southern half of state, we're gonna talk about what's going on with our soils, especially in terms of water and some areas where it's also dry. Then also later on, we'll talk about what's going on with diseases a little bit and how that's been played into a little bit with the wet conditions we've had. These sessions are brought to you by, generous support from University of Minnesota Extension and from Minnesota farm families through our Minnesota Soybean Research Promotion Council as well as the Minnesota Corn Research Promotion Council for funding support. So we wanna thank those folks as well.
Anthony Hanson:And we're glad you could join us. I'm Anthony Hanson. I'm a regional extension educator in integrated pest management. And we also have our two guests on today. We have Brad Carlson.
Anthony Hanson:He's a educator with, water resources, works a lot with, soil nutrients. And then we have Dean Melvik. He's our extension plant pathologist. He will be kinda covering the latter half of things here. So we'll be starting off with Brad in just a little bit here.
Anthony Hanson:So I think with that, if you do have any questions that come up during the session, feel free again to put that in the q and a box. We have a few questions folks have emailed to us as well. So we'll kinda start with those a bit here. So, Brad, I think I'll start with you. And I guess just quick little weather update.
Anthony Hanson:Looks like we're getting even more rain this morning here. I'm hearing about an inch to two inches for a lot of folks, it looks like here.
Brad Carlson:Yeah, I was just on the, in fact, I've got on my other monitor, if I glance to my left, I can look at the radar right now. It looks like West Central Minnesota is getting some pretty good rain, I guess, not particularly heavy. There's maybe a little bit in some spots in Redwood County and Meeker County where the radar is yellow, but fairly consistent coverage. However, the National Weather Service map this morning did show that there's some places in Minnesota that are probably going to be getting as much as four inches of rain. Obviously, that's just a projection.
Brad Carlson:However, it looks fairly consistent across the Southern third of the state that a lot of it's going to be getting about two inches, you know, so we're kind of there. We know that this is the time of year when people are doing side dress nitrogen. As I drove into the office this morning, I had a neighbor who was putting on some side dress nitrogen, hoping to get it done before the rain hits here this morning with drop nozzles and 28% or 32%, whatever the case may be. And I know that across the state, there's pretty much everybody who planned on putting on side dress, either already have it on, or you're looking at trying to get it on here in the next week or so. Typically speaking, we look at targeting, you know, roughly V4, V six, we're kind of past that almost everywhere at this point with the corn.
Brad Carlson:And so really the timing is fine regardless, you know, we kind of like to remind farmers that we don't think there really is any such thing as spoon feeding nitrogen. Your nitrogen is either available or it's not, really doesn't matter when it went on, you know, so as far as delaying an application for any reason, you know, the only reason to delay is if you think there's a chance that you're going to lose it. And, you know, so we've kind of talked, you know, for the last several years, you know, even as early as say, middle to late May, you know, if you're done planting and you plan to side dress, you know, the difference between doing a side dress in May 20 versus June 6, the odds of losing nitrogen in that period of time is very small, you know, and so, you know, you're better off just simply getting it on. Again, that's kind of a moot point at this point, because a lot of that corn is getting towards about knee high, you know, probably what's of more interest is on the backside of that, you know, and so we're looking at V10, V12 typically is the cutoff period when we start getting towards tasseling.
Brad Carlson:Now, at that point, the corn's kind of through its rapid growth phase. And so we really need the nitrogen applied before that happens, you know, particularly if, if there's significant amounts necessary, you know, so, so this is good time, depending on how wet it gets now here this week and, and throughout the week, you know, I guess we'll have to kind of see how fast the corn grows. However, you know, again, the timing is pretty good right now. And, you know, from that standpoint, I guess it sort of depends on what kind of equipment you've got available for doing the applications. I know one of the trends has been lately for farmer owned equipment and that's created a lot of ability for a lot of farmers to do their own side dressing, you know, just simply looking at, you know, timeliness is no longer an issue.
Brad Carlson:You're not waiting in a list for either your fertilizer dealer or for a neighbor to get around to you, you know, and so from that standpoint, there's not a lot of risk as far as getting it put on. Most of the folks who have their own spraying equipment are typically doing some kind of a drop nozzle, whether it's a Y drop or just simply a drop hose of some sort and dribbling on 28% or 32% UAN. I haven't seen a lot of farmers who have spin spreader boxes. There's a few of them out there, but a lot of the commercial application that goes on this year is simply top dress with a spin spreader box and urea just kind of thrown out on top. That's a fine application to realize that when you're throwing urea on, you know, into the corn world, you're going to see some streaking and some burning.
Brad Carlson:We haven't seen really any evidence that that's likely to cause any yield damage. Question becomes using an inhibitor. Obviously this time of year, nitrification inhibitors typically are not a product that we look at using because the corn needs the nitrogen right away. It's the urease inhibitors we worry about. The urease process is particular to using urea.
Brad Carlson:It's the chemical, biological chemical process by which the urea molecule gets cracked into its inorganic forms. And one of them initially is ammonia, which of course is volatile and will blow away. And so the urease inhibitors, again, simply slows that process down. Urea, know is soluble in water. So as long as you're getting some sort of precipitation, it of course is going to dissolve the urea.
Brad Carlson:The key though, is we want enough precipitation to then carry it into the soil, probably a quarter of an inch, if you get light levels of precip or just simply do, that's actually worse because it dissolves it and just simply spreads it out thin across the surface. And so the urease inhibitor can help with that. Since the patents come off on a lot of those, the primary products, the prices really come down. I know, like for our research standpoint, we just always use it just simply as a matter of just in case, you know, it was necessary, you know, from a farmer standpoint, economics is a little bit questionable right now. You know, I think really, if you look at the weather forecast and so like for instance, if you were spin spreading in Southern Minnesota this morning, no reason to be investing in the urease inhibitor, it's gonna rain.
Brad Carlson:And then, you know, it'll push that urea down into the soil and you're not gonna lose it. You know, if the forecast indicates sunshine, you know, we typically say, you know, four days, however, we know we've got evidence for instance, at Waseca, we did some a couple of years ago in some really hot weather, whether it was in the nineties, up towards a 100 degrees. And we were actually seeing some nitrogen loss, like within twelve to twenty four hours. And so really there is a little bit of a temperature dependence on that. However, if you're, again, if you're spin spreading top dressing urea right now, you know, again, look at the weather forecast and then kind of decide for yourself whether you want a urease inhibitor with that product.
Brad Carlson:So that's really the main things. I did get a question from a farmer earlier in the week, and it's maybe a moot point by this morning, but the question I got was, should I be side dressing my UAN right now or wait until after it rains? Now, really the caveat here is this specific farmer told me that the color of the corn looked great. You know, loss processes of nitrogen are water driven, and it happens when the soil is completely saturated. Now, you know, coming into here this morning, there's a decent capacity across a large part of the state to absorb this rainfall, or at least some of it.
Brad Carlson:And so the risk is not real high. The odds, particularly of leaching it, aren't high at all. However, you know, if the soil capacity is one to two inches and we get an excess of two inches, we can look at denitrifying some of that nitrogen, and that is temperature based. It's a biological process. A lot of the soil temperature now is towards 80 degrees.
Brad Carlson:And so it's a time of year when we have a high risk for denitrification losses. Now, my advice to this particular person, because he's got his own application equipment, the corn looked great. I said, you might as well wait, you know, just, you know, wait until this rain is through and then put it on. Because if you put it on and then you get a big rainfall, you could maybe lose some of it. Remember, UAN, 25% of the nitrogen in UAN is already nitrate and it's nitrate that we lose that either leaches or goes through the denitrification process.
Brad Carlson:Urea is a little different. It's got to get converted to ammonia, ammonium, and then to nitrate, you know, that's kind of a different thing, but from the, you know, dribbling on that 28%, 32%. Now, you know, in terms of is that loss, the the risk of that loss really great? Probably not, you know? So, if you're getting a custom applied, if the dealer's putting it on, you know, you're probably better off just getting it on, you know, rather than risking it getting a little bit too late.
Brad Carlson:But it's, you know, it's, I guess it's a little bit of semantics from that standpoint.
Anthony Hanson:So Brad, I got kind of at least two questions here before we switch over to Dean. And when I was thinking about I know here by Wilmer, we had about eight inches of rain, they said a little over a week ago, think now. And what's what's kind of the dynamics of nitrogen or basically our overall soil chemistry when you have these areas that we've been getting consistent rains and cheer there versus eight inches, even if it kinda if it drains out enough where it's not completely flooded, what's kind of at risk nutrient wise in those areas if we see heavy rains like that?
Brad Carlson:Right, and I'm aware because I was up to Wilmer here yesterday, you know, there is definitely is a pocket as you kind of go from Hutchinson up towards Wilmer that really got soaked, and there's a lot of water standing. Denitrification happens when the soil is completely saturated. So, you know, when those big rainfalls happen, of course, that was widespread across the field, Really then it's a time factor. So this is kind of where your drainage is kind of helping you out as far as keeping it from being completely saturated for long periods of time. However, in those low areas that are flooded, denitrification loss has been fairly significant and you can actually see some yellow corn in some of those places.
Brad Carlson:You know, the caveat of this is a lot of them low spots now they flooded out too. So yeah, you're losing all your nitrogen down there, but there's no corn either, and it's getting a little late to be doing any kind of replant in there. You know, I guess from my standpoint, I do not, even though the rainfall was extreme, I don't think that we've had enough time and thorough saturation that we need to be talking rescue treatments. We do have a help sheet available on our nutrient management webpage that can help you walk you through that. So sort of depending on what practices you did, you can kind of assess the risk level for that and it looks at application timing.
Brad Carlson:And, you know, if you're a person who really kind of shaves it close on rate, you know, you might want to think about it. But if you had a healthy rate of nitrogen and your application timing was good, I just, I just don't see there's a great reason to be looking at, at doing a rescue treatment. Well, there's been some discussion about the pre sidedress nitrate test going in and doing a soil sample for that. You know, the problem with that is we've had a lot of issues with not so much positives, because if you find the nitrate, it's pretty comfortably there, but there can be some tie up from immobilization, from decomposition of soil organic matter, and it can occasionally give you a low number when there's actually more nitrogen, but that could be a tool, you know, again, probably don't have time to go through all the details of pre side dress nitrate test right now. However, Fabienne just put a press release out on that about a week ago.
Brad Carlson:You can take a look at that if you want.
Anthony Hanson:Yeah, thanks, Brad. I think we'll move along to Dean. We'll talk about disease things. Yep, again, thanks, Brad. If you're hanging on, we'll see if we might have another question or two that comes So either Dean.
Dean Melvik:Hello, good morning, everybody.
Anthony Hanson:Alright, so, we've had a couple questions coming on the disease side too. But yeah, if you want us to give an overview of what especially June has been looking like in terms of early season disease risk, but also what are we being set up for when we have kind of this much consistent rain in June, across at least most of the state, I want to acknowledge that Northwest Minnesota, those folks sounds like they could use a little more rain, not as strong of storms are the ones that have come through. But yeah, we do have some dynamics across state where it's not wet across the whole state, at least.
Dean Melvik:Yeah, yeah, good point, the way you frame it there initially, you know, we're kind of in the in between period when we often don't see a lot of disease and crop fields, we often see in the early season diseases and then the later season ones, which are generally most important. But if we talk a bit about the early season diseases first, you know, one that we're concerned about that a lot of seed treatments are active against this Pythium root rot. You know, that's a cause for seed early damping off or seed rot in the ground. So we're pretty much past that phase. If we have a good stand right now, that probably is not going to be having much of an effect.
Dean Melvik:Something we could be seeing now where we've had enough rain and now the warm soils would be both Rhizoctonia root rot and Phytophthora root rot, both soybean diseases. Now the Rhizoctonia is one that you'd be recognizing it now by it's killing plants and could have been killing plants in two weeks, last two or three weeks in fields. I was at my research trials in Waseca last week and they're focused on rhizoctonia and we have considerable stand loss in some of those. So we've had ideal conditions for rhizoctonia there, I'm sure in other places as well. And I mentioned Phytophthora, that's something I think a lot of people are aware of, see that kind of scattered across some landscape too, and that's definitely favored by wet, virtually saturated soil conditions for some point, and then warm soil.
Dean Melvik:And so we have conditions ideal for that too in many places. We may see it now, or we may see it later in the season. This is one of those few diseases that we can see throughout the entire growing cycle of the soybean. And a couple of things to point out there, we manage that largely by resistance. So every bag of soybean, every trait description for a variety has two basically two data points for a VITOPHTER resistance.
Dean Melvik:One is so called RPS genes, major resistance, major genetic resistance. And then the other is field tolerance or partial resistance. And so those numbers are important in determining how that variety will react and survive in a field that's subject to severe Gytophthora stress. And so the thing I want to say about the RPS genes is that we've been getting more and more reports and evidence that the Phytophthora pathogen population in soils across the state is gaining abilities to overcome more of those resistance genes. So if you have a problem with that, take note of which resistance genes you have and consider changing that in the future.
Dean Melvik:There are some various options out there and I won't go into all the details now, but we could go into that more another time if you wish. So moving ahead, looking ahead, as Anthony noted, what we set up for later in the season when a lot of our major soybean problems, diseases at least seem to occur? First one that comes to mind is sudden death syndrome. We've had very good conditions, wet soils early after planting, periodic rainfalls after that. This is a good setup right now for SDS in a lot of areas.
Dean Melvik:Certainly not everywhere, but that'll be something to watch out for. But we also noted that even though we might have ideal conditions early in the season to set it up and even initiate the infection of the roots, if it dries out severely in late July, early August, the disease usually doesn't develop very much. So a lot of the disease picture comes later on, it's dependent on the weather in July and the August. So what happens now has an effect, but what happens later even has a greater effect. So that's why it's very difficult to predict.
Anthony Hanson:We had a related question come in, Dean, partly asking about wet conditions now, but also the dry winter we had, did that help us out with some diseases at all? I imagine some it probably doesn't matter much at all during the winter.
Dean Melvik:No, I would say probably that wouldn't have a big effect. In fact, some of our fungal pathogens survive best in the lab when they're desiccated. So they're not subject to any attack by other microbes, for example. And so they do quite well in a lot of different conditions, including cold, dry soil.
Anthony Hanson:Yeah, another question I had was about no areas where we've had either outright flooding fields at least or just enough moisture saturated fields where do you get some of these pathogens that are moved by the water more so or are most of these more just airborne later on when they go through their life cycle?
Dean Melvik:That's a good point. Know, lot of these soil borne pathogens are moved by anything that moves soil. That could be overland, below water, it could be windblown soil, could be overland flooding. Yes, all those that can move pathogens around from field to field and even greater distances in some cases. Yes.
Dean Melvik:And then moving on to corn, we focused there a little bit on soybeans and just some highlights, but on corn, you know, we occasionally do have severe seedling diseases in corn, although unfortunately that seems to be pretty rare. You know, a number of years ago there was a big problem done by around Mapleton, But that hasn't occurred again, as far as I'm aware. But occasionally we have issues and I didn't hear much this year, so we're past that stage. A couple of things to point out is, you know, certainly having wet residue in the field can help the pathogens that are surviving on that residue produce spores and then spread into the new growing foliage. It doesn't need a lot of rain, but continuous moisture can help that process.
Dean Melvik:So it might help early infection as well as the wet foliage that can enhance early infection of some of the leaf diseases. Even though we don't see symptoms, we don't see a lot of signs of infection usually until later. And so that's a general comment. Now a question came in about tar spot and I'll get to that in a moment. But just one thing I'll mention, some of you are aware of a disease called crazy top of corn, which occurs under very wet and even if it's flooded.
Dean Melvik:If the pathogen can get into the world as the flooding occurs, that can be introduced that way or even by the rain splash perhaps. We don't see it a lot in Minnesota, the fact it's rarely been reported, but there are a few reports and it might be something to watch for in the areas that received a very large amount of rain, for example, the Wilmer area. And then getting to tar spot, kind of our mar disease these days because it's new and a concern and spreading on corn. Again, like I said before, what happens later in the season is going to drive how severe that is. And, you know, we seem to need some we need some level of moisture as we've seen in previous years.
Dean Melvik:In the drought year, two years ago, we saw very little tar spot. Last year, 2024, we saw a lot more rain and we saw a lot more tar spot, but tar spot didn't occur everywhere. There was a large amount of rain. So it needs this proper combination of enough moisture and also cool enough temperatures. So, you know, we're developing and improving our abilities to predict that disease, but there's still a lot we don't understand.
Dean Melvik:But what we do know is based on the distribution of where the disease was found last year, the pathogen is very likely surviving in fields across most of Southern Half Of Minnesota. So the risk is greater, for example, in Western Minnesota than it was a year ago because the pathogen is probably there in a number of fields. That doesn't mean it's going to cause problems and yield loss, but it's more likely we'll see it. And the last point I'll bring up there is, for those of you that kind of watch the national distribution, there's a map it's called on the corn IPM pipe. You can find that on our website.
Dean Melvik:You can find out where tar spot has been reported so far this season across The US. The closest we have so far is Southern Iowa and Eastern Nebraska. So tar spot has been found in a number of places there, not in Northern Iowa, not in Wisconsin yet, not Northern Illinois or South Dakota or North Dakota, not anywhere near our borders, but it is developing in the Midwest. And there's no reason to think it couldn't be developing in Minnesota. Something to watch for.
Anthony Hanson:Yeah, Dean, talking about just maps last year, especially wasn't last year, the year that we started seeing tar spot show up for the first time in counties in Western Minnesota, that map really seemed to expand compared to previous years.
Dean Melvik:That's correct. That's correct. And over into South Dakota and North Dakota as well.
Anthony Hanson:Yeah. So So it's like you said, didn't seem like it was high levels, but just seeing that map expand that, you know, was concerning at least there. I got one question that came in, Dean, you could comment on this or possibly Brad too, but corn that's been standing in water for a week. We've had a few growers having that seeing that firsthand and what could they expect for yield reduction or diseases possibly in those cases? You mentioned already-
Dean Melvik:I'll start. Brad, you can finish. I haven't seen a lot of connection there between that and disease. That's real clear. I'll just stop there and Brad, you can take it from there.
Brad Carlson:I guess, if it's been in standing water for a week, I'm questioning if it's still alive. Yeah. You know, there's kind of that, you know, in general, if it's been that bad, you're probably talking about corn that's gonna end up chest high, you know, it might get 30 bushels an acre. You know, the problem with a lot of these areas, I mean, we can describe maybe what happened with the nitrogen and a lot of it probably was lost. The question becomes what's the yield potential anymore anyway?
Brad Carlson:Is it really worth throwing good money after bad? And all and that that's really the key. You know, if the soil was saturated and the corn looks generally okay, again, we can lose at 80 degrees, at 80 degrees soil temperature, you can denitrify almost half of your nitrogen in about ten days. Now ten days is a long time for the soil to be completely saturated and the crop not to be dying or dead. However, there are some years, last year that did happen.
Brad Carlson:And I think in 2016, it also happened across some wide areas. But again, I would really, I don't know what the yield potential is, you know, without getting into it, but in the past, you know, those areas just typically aren't worth throwing any additional resources at. All
Anthony Hanson:right, Dean, I had a question on white mold a few times in the last few weeks. Just wondering if this is setting us up for higher risk for that. I don't if you want to mention that just briefly, you know, life cycle on that kind of where that would be a higher risk or what we need to look forward to, especially in coming weeks here on that one.
Dean Melvik:Yeah, that's certainly a widespread problem across much of the state. Again, general comment, what happens in July, early August is going to really drive white mold as well. And so just a bit of the life cycle, I was out in a soybean plot yesterday, soybean plants are getting fairly large now. They are not filling the rows yet, but if they were 15 inches rows, they would be starting to get pretty close. So remember the white mold pathogen survives in the soil.
Dean Melvik:When the soil is shaded and moist enough, it will germinate and produce this little mushroom like structure under the plants. Okay, so we need moisture, we need shading generally, and those spores produced on that will then go on to the foliage or especially the dying flowers and start infection. So we need that sort of combination of factors flowering, cool enough temperatures with ideally even 70s and not much in the 80s at all. And then you know enough moisture to keep the soil moist and the plants moist and then we can get white mold developing. So that is that, you know, the time is getting close.
Dean Melvik:So if someone were to be considering a fungicide application, remember don't put it on too late nor too early. Know, we used to say R1, R1 generally is too early if it's unless it's the very end of R1, but late R1, R2 was probably the optimal time we're gonna choose one application. So we wanna proceed the infection with the fungicide application.
Anthony Hanson:All right, thanks Dean. We don't have any other questions coming in. So we caught up with the ones that did come in. So thanks folks for submitting those. And, again, thank you, Dean and Brad, for joining us quick this morning here, and, we'll have future sessions coming up here too.
Anthony Hanson:So I'll mention that in a little bit. But, again, thank you for all the attendees here today for our University of Minnesota extension field notes program. Again, wanna thank our sponsors, the Minnesota Soybean Research and Promotion Council as well as Minnesota Corn Research and Promotion Council. And, again, when you log off, there'll be that quick survey. Please take just, you know, a minute or two to fill that one out.
Anthony Hanson:And then next week, we will be talking about iron deficiency sclerosis and fields where that's a specialty problem. So it'll be a major focus there and what's going on with basically keeping our soybeans green out there. So, again, thank you. Have a great rest of the day, and we'll see you all next week.
