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Welcome to University of Minnesota Extension's Nutrient Management Podcast. Each month we bring you the latest research in nutrient management for crops and how you can incorporate the latest tips and best management practices to your farm.
Hello, welcome to the Nutrient Management Podcast from University of Minnesota Extension. I am Jack Wilcox in communications with Extension.
Jack Wilcox:We've had some significant rainfall in parts of Minnesota recently, and we wanna talk about the impact of that precipitation on crops and inputs. We have three specialists and educators to help us. Could you introduce yourselves, please?
Brad Carlson:I'm Brad Carlson. I'm an extension educator at the Biancona regional office, but I work statewide extensively with nitrogen management and and then crossing over into the water quality impacts too.
Daniel Kaiser:This is Daniel Kaiser. I'm a nutrient management specialist located out of the Saint Paul campus.
Jeff Vetsch:Hi, this is Jeff Vetsch. I'm a research supervisor here at the Southern Research and Outreach Center focused primarily on nitrogen.
Jack Wilcox:Okay, let's get right to it. What adverse or severe weather conditions did Minnesota actually experience in this late June, early to mid July timeframe?
Jeff Vetsch:Yeah, so in mid to late June, we did have some hail that went across the path around Highway 12 in that area, Highway 7. I think it was a pretty wide swath in some spots, and pretty nasty hail from the pictures I saw that certainly would have have, affected any of those crops that were growing in that area. But when we think about the the more recent, concerns related to the heavy rainfall, especially in Southeast And South Central Minnesota. It kinda initiated there at the end of June, but primarily the period was July 1 through the third. There was some pretty heavy rainfall, then again, the eighth through the tenth.
Jeff Vetsch:This hit primarily in Mauer, Fillmore, and Houston Counties. And when I looked at the weather reported precipitation from June 28 or twenty ninth through July 10, for some areas, this is what I came up with. For the SROC here at Waseca, we had about four and a half inches. At Albert Lea, 6.2 inches for that same period. Austin, 10.2 inches.
Jeff Vetsch:Grand Meadow, just East of Austin, 11.3, including 7.3 inches at Grand Meadow recorded on the the July 2 in one twenty four hour period. Preston, also Minnesota and Fillmore County 11.3 inches, Caledonia nine inches including 6.7 also on July 2. Altura which is in Winona County 6.3, and Rochester six inches. And then as you come back to the west on Highway 14, that four to six inches is pretty typical all across that area. So yeah, some of these areas got a lot of rain in a short period of time.
Jeff Vetsch:And certainly some of those areas needed some rain, but not nobody needs 11 inches in, in in ten days.
Brad Carlson:Yeah. And I and I think we know that we came into this the year with a a general moisture deficit. I don't think anybody was really that concerned about it, but there was a general moisture deficit, meaning that the soil profile had a lot of capacity to absorb water. I had a chance to look at the drought monitor here this morning before we started recording, and and it does still show anywhere from minor drought to just abnormally dry in the Southwestern corner of the state. I think we've all heard about, you know, the boundary waters area getting closed and it being really dry up there.
Brad Carlson:But when you look at the drought monitor and if you know your Minnesota geography, there's not a lot of crop production in the areas that are really in the the worst drought areas in Northern Minnesota. So from, you know, an ag perspective, a farmer perspective, that that's not impacting much. Northwestern Minnesota, the Red River Valley, actually shows nothing like up in Kitson County, and then it just kinda says abnormally dry as you go a little south. I, just yesterday, I drove Highway 60, which, if you're familiar with it, is kind of an arc from Worthington up to, Mankato, and I noticed no moisture stress signs, in that drive.
Jack Wilcox:Let's switch to talking about crops. How are the crops actually doing?
Jeff Vetsch:Well, I think from a from a growth stage, the the hail that was received in mid to late June, the corn was probably in that v seven, eight, nine stage. So hail could obviously defoliate, but the plants had some ability to put on some more leaves if they didn't die. Probably tougher for beans. Now this more recent heavy rain, the corn was anywhere from V 10 to V 15 here this last late last week. Even some tassels starting to show in some early planted fields.
Jeff Vetsch:So the heavier rain in those in those cornfields at this later date probably isn't as detrimental other than the fact that when it comes, as Brad mentioned, so crazy intensively, you know, some of these places get two, three inches in a matter of a few hours, you do have erosion and you got some gullies that you might have to watch out for and things like that. The corn can probably stand a heavier rain at that time of the year better than soybeans, certainly. Oh, there was one other place that I forgot to mention about heavy rain, Morse, which had been extraordinarily dry through the early spring and were begging for rain, did get very heavy rain back in mid to late June more than they wanted. And that did result in some flooding I heard in some of their areas. But that was pretty isolated, not even the whole county, just some small areas.
Brad Carlson:And I think it's also pertinent to this discussion. We were talking about a little bit before we started recording that we were coming into the year with a drought with a a moisture deficit. And it it did tend to and that didn't really alleviate until, you know, heading towards June. We we still had pretty good capacity in the cell profile to absorb water. That led to some pretty deep root growth.
Brad Carlson:We we we assume from the the corn crop. And so, you know, from that that perspective, you know, we look at probably being more efficient with nutrient use, the ability to get nitrate that might have gone deeper in the profile, and probably gonna serve us well going in the week or two ahead as we look at the the currently at the forecast and not seeing a lot of precipitation in and out seven days or maybe a little longer.
Jack Wilcox:Dan, how did the heavy rainfall affect the nutrients or inputs that were already in the field?
Daniel Kaiser:So normally, with excessive rainfall, we have concerns related to leaching of nitrate and also denitrification, which is a bigger issue for soils that you see a lot of ponding for extended periods of time. The thing about though when it came this year is if you look at the growth stage, for most crops is usually the later on we are, the less impacted we should be with particularly particularly with with denitrification, and that's mainly if you look at the uptake of nitrate out of the soil from the fertilizer you apply. There's a few pieces of data that I show at some of our meetings that Fabian Fernandez collected where they took samples at around r one growth stage. So, you know, looking at early silking and the amount of nitrate in the top foot of the soil, really, really, look at the rate that was the optimal for that given field is similar to where no nitrogen's been applied. So, I mean, really, that point in time, the crop, because it's rapidly growing and taking up nitrate at that point in time, has captured most of the fertilizer that should be in place.
Daniel Kaiser:And then anything that the crop needs post r one likely is coming from mineralized nitrate because we know that the uptake tends to slow down once you get beyond that growth stage. So, you know, generally, you know, if you're looking at rainfall events late June, early July, they always say knee high at the July 4, but anymore, I mean, the corn, I with the or as early as you're planting as fast as the crops grow, we're generally at close to tasseling at that point in time that most of the nitrate is taken up. So I'm really less concerned, really, the later it is. I mean, really, when we get to early June rainfall events are really where we're gonna see most of the impact. And I know that's some things that we saw, I think, last year in some areas with more saturation, where it makes more sense than to be worried more about the the supplemental applications.
Daniel Kaiser:I mean, you might see some yellowing out in fields that were ponded, but a lot of times, oxygen deprivation will cause some deficiency symptoms similar to nitrate. The soils dry out. Plants start to grow out of it. I mean, the question is, those areas, if they're isolated and small, it really isn't worth going out and making any corrective measures on most of those because it's just gonna be a lot of time and effort for a situation where, you know, probably if there is a yield reduction, it isn't anything related to the nitrate that was that was being lost.
Brad Carlson:And it kinda leads into a general discussion that's happened in the last decade or so about whether late season end has any kind of benefit. And, you know, we've always said in Minnesota, we don't see a lot of advantage of that. I think it's it's pertinent to this discussion because the reasons why we don't see any advantage to that is also pretty much the same reasons why if you thought you had some nitrogen stress because of the the the wet soils, you're probably not gonna see much of an advantage of that. And I know we had a couple years ago, we had some extremely wet conditions early in the growing season, early enough that we felt we really needed to address it with rescue treatments. Jeff, you were able to respond to that with a little bit of kinda impromptu research, and and I thought the results of that were pretty instructive.
Jeff Vetsch:Yeah. We we put out a couple of kinda, you know, like you said, reactive type studies on fields, and that was in 2024 when in here at ESROC, we saw we received 20 inches of rain in May and June that year, just brutal. And, you know, we had N deficient corn everywhere, and the the region around us was very similar too. So, yeah, we put out some trials and we put the n on probably around the July 1 and the crop was anywhere from v eight to v ten, eleven. So it was it it had was taken up some end but it needed a lot more end to get to the finish line.
Jeff Vetsch:And we did see modest fuel responses up to 15 bushels or so, but some were like only eight or 10. And when you looked at the cost of the application and the treatment and the crop price for corn at that time, most of them paid, but it did not give a huge return on investment. But it did give a modest return. So as you said, Brad, and to kind of reiterate what Dan said too, is that the crop, the fertilizer N we apply kind of feeds the crop during those early stages, like the May and early June, and then at that point the crop really relies as it gets more mature on and from the soil. So when you lose all your fertilizer in in early June, that's a huge or due to leaching or denitrification, that's a completely different thing than having excessive rain in early July, especially as far along as the crop is this year when we already have tassels in most of our fields around here today.
Brad Carlson:And, Jeff, where you did get a yield response, how much nitrogen were you applying?
Jeff Vetsch:Oh, yeah. That's right, Brad. It was a pretty low rate, and we put on, I think, zero, thirty, sixty, and ninety or something rather. And typically, lowest rate, 30 pounds of actual and not pounds of product, was all we really needed in most of those fields. So it doesn't take a whole lot.
Brad Carlson:Yeah. And see, and I think that that just illustrates the point of how much nitrogen can be supplied by the soils because, you know, a lot of people were thinking, oh, we lost it all. You know? But, really, you didn't get any benefit from an extra 60 pounds of nitrogen after that first 30. That meant that that slack was being taken up by the mineralized end from the soils.
Brad Carlson:And so same situation we're in right now. If you do have some wet soils that look like they're they're may be getting a little bit of nitrogen stress, You know, we're we're currently in a condition to kinda kick that mineralization into overdrive between the temperature and the moisture in the in the upper profile. We're gonna be seeing a lot of mineralization of nitrogen here in the in the next several weeks.
Daniel Kaiser:Well, the price of nitrogen too. I mean, right now, I just it's it's probably not worth much of a consideration for these in season applications. And I know, Jeff, I mean, when you were doing it a couple years ago, nitrogen is a lot cheaper. So, you know, economically, that I think that's the main consideration to make is whether or not you're gonna get enough out of it. And just from the data we have, I mean, the I think the the risk for being short the later on you go is is relatively low that unless you visibly see some deficiency symptoms that are related in these areas related to nitrogen.
Daniel Kaiser:I mean, it just looks like this year is we're gonna have this is good as this year is. I would bet mineralization could satisfy a lot of what we need. So I just I'm less concerned about I mean, the main issue really would be in some of those areas, particularly in the Southeast would be washing, erosion in some of those areas, for for corn that you know, a lot of that probably didn't get in the soil anyway to cause some of the denitrification. So so unless you're really seeing major issues I mean, we're at a situation where in season or late applications, we just seldom see any benefits. And just going back to, you know, probably ten, fifteen years ago, I know there was some work looking at some wetter years, some of these late post tasseling applications in situations where the, we had some of these rainfall events, so there just wasn't any benefit yield from those late applications.
Daniel Kaiser:So you're just throwing money at something that the nitrogen's likely gonna be there in the fall sitting in the soil and not being utilized. So just just some things to think about with with corn. It's really an issue of timing when that this rain occurs where it's most of an issue.
Jack Wilcox:What about different soil types? How do they deal with heavy rainfall?
Brad Carlson:Well, I think it's important to remember that we have different nitrogen recommendations, particularly if you have coarse textured soils. So with in irrigation, we recommend multiple splits. And particularly, if if you've got an irrigation system and you're able to fertigate, it allows for a lot of splits, you know, more or less every time that irrigator goes across the field, you could be putting on some nitrogen. But but the thing is is this probably was the game plan on a lot of those light textured soils just to potentially still be applying. I mean, we're kinda getting to the point now where, you know, may maybe you've got enough.
Brad Carlson:But, you know, there's still a significant amount of nitrogen to be taken up, by the crop. And and if it's a low organic matter soil prone to lose nitrogen, it is probably gonna still need some. So from that standpoint, I mean, the coarse textured soils are just a different just a different thing. The heavier textured soils, it's gonna be a mixed bag. I mean, a lot of that stuff is is pretty extensively drained across most of the state, and so it's going to respond well to a lot of precip as far as just getting rid of that excess moisture and it not creating a problem.
Brad Carlson:You know, Dan and Jeff already talked about the fact that, a lot of the nitrous have been taken up already, and so there isn't really a lot there to be lost. So as far as seeing a lot of leaching into the tile this time of year, probably aren't gonna see significant amounts of that being lost to the environment either. But it's worth noting that the heavy soils where we have a lot of our drainage are also prone to stay saturated even with tile depending on how much it's raining and how often. And those are the spots where we would denitrify and lose some nitrogen. You know?
Brad Carlson:So I I I hate to use the d word. It depends too much, but, you know, it's gonna there's gonna be some variability as you go across the state based on what your soils are like.
Jeff Vetsch:Yeah, Brad. And I I went and looked at all of my end studies in Southeast Minnesota after the first heavy rainfall there, those first few days in July, and I did not really see any detrimental obvious end deficiencies a couple days afterwards, or five days afterwards. But I would also say that, you know, as Dan mentioned, I think one good thing to think about is when your field does sit in some saturated soils for several days, no matter how good your tile drainage system is, you may see some lack of oxygen in that in those lower leaves might slough, and I did see some of that. And I think that's not necessarily related to nitrogen deficiency always as it is to just the crop is is doesn't have the air in the soil that it needs and it takes a few days to dry out to get that oxygen back in the soil so the plants back to being happy again so to speak. So so do be cognizant of that too and don't if you see some yellowing lower leaves at the very or sloughed lower leaves at the very bottom of the plant, part of that is just the natural senescence as the crop gets to its reproductive stages in corn, and then the other part is just the fact that it did sit in some some pretty saturated soils in some of these fields for several days.
Jack Wilcox:Jeff, what was that word you just used?
Jeff Vetsch:Senescence, s c e n s c n. Can't spell it. Maturity would be a easier word.
Daniel Kaiser:Yeah. I think it's s c e n e
Brad Carlson:This would be some real magical, podcast moment here. Four guys trying to figure out how to spell senescence. Just use spell check and let it change it for you.
Jeff Vetsch:Yeah. We we collectively, we have how many degrees and we don't know how to spell senescence.
Brad Carlson:And and it's a word we use a lot too.
Jeff Vetsch:Yeah. Yeah. At least we know how to pronounce it.
Brad Carlson:What it means. I don't need to know how to spell it.
Jack Wilcox:How did this rainfall event stack up in terms of triggering crop insurance?
Brad Carlson:Well, if we look at the the extent to which this there's anything going on out there that could be an insurable event, I mean, in general, you know, there of course, there's probably some there's pockets of hail out there that are gonna be affected greatly. But from the rainfall perspective, you know, we've had no disasters declared, so there's not gonna be any special assistance, you know, from that angle. Probably more in the range of total crop revenue coverage. I think we know with the economics being a bit sketchy kinda depending on where you're at as far as, you know, your expected price and so forth. I I'm you know, what we typically find if farmers think they're getting close to the threshold where they're gonna be collecting on that, probably not gonna go pour a lot more money in the inputs and potentially just put, you know, good money after bad.
Brad Carlson:And so, you know, as we're kinda sitting here saying, you know, there's really not a lot of scenarios where we would recommend putting on any more nitrogen this year other than the people who had already planned to do so because they have irrigation. I think that does play a factor in there that that just you know, if if you've got total revenue coverage, crop insurance, you're probably not gonna wanna just throw another extra chunk of money at your at the crop and probably not see much or any of a return whatsoever.
Jeff Vetsch:Yeah. The only sidebar to that, I would say, Brad, is in my in my road trip to Southeast Minnesota last week, I did see some drowned out spaces or spots in several bean fields and some kind of washed out soybeans. So those might be areas where possibly you could get a revenue adjustment. But most of the corn actually took it quite well except for maybe some fields that that got drowned out more than once that were, you know, as an example, maybe the Blooming Prairie area, they got heavy rain there back in late mid June and then again last week. So those areas maybe saw some drowned out areas.
Jeff Vetsch:But for the most part, the corn crop looked quite good. And And what I looked excellent all year, to be honest.
Brad Carlson:Yeah. And kinda what I'm seeing for drowned out spots is it's primarily the places that drown out every year. You know? So it's probably not much different than what what most guys know where those areas are in their fields, and they just come to kind of accept the fact that three out of five or four out of five, there's there's gonna be enough rain that those spots are gonna hold water and create problems.
Jack Wilcox:You just heard Brad Carlson, Extension Educator out of Mankato, Dan Kaiser, Extension Nutrient Management Specialist in Saint Paul and then Jeff Vetch, Lead Researcher for the Southern Research and Outreach Center in Waseca, Minnesota. Thank you all for being here.
Jeff Vetsch:Thanks, Jack.
Brad Carlson:Thanks, Jack.
Daniel Kaiser:Thanks.
Jack Wilcox:Do you have a question about something on your farm? Just send us an email here at nutmgmt@umn.edu. Thanks a lot for listening and we look forward to seeing you next time.
Jack Wilcox:We'd like to thank the Agricultural Fertilizer Research and Education Council, or AFREC, for supporting the podcast.