SCN + Phytopthora and manure
I'm Ryan Miller, Crops Extension Educator. Earlier this morning, we recorded an episode of the Strategic Farming Field Notes program. Strategic farming field notes is a weekly program addressing current crop production topics. A live webinar is hosted at 8 AM on Wednesdays throughout the cropping season. During the live webinar, participants can join in the discussion and get questions answered.
Ryan Miller:An audio recording of the live program is released following the webinar via podcast platforms. Thanks, and remember to tune in weekly for a discussion on current
Dave Nicolai:Again, welcome to Strategic Farming Field Notes. This is a program from the University of Minnesota Extension. These sessions are brought to you by the University of Minnesota Extension with generous support, from farm families throughout the state of Minnesota and also by the Minnesota Soybean Research and Promotion Council and the Minnesota Corn Research and Promotion Council. So we're happy that you're joining us for today's session here on, soybeans, soybean cyst nematode.
Dave Nicolai:We'll talk a little bit about soybean diseases and, also about manure and nutrient management, as well. My name is Dave Nicolai, and I'll be monitoring, today's episode. We have 2 guests that will be with us today, Bruce Potter. Bruce is the extension and integrated pest management specialist out of our Southwest Research and Outreach Center at Lamberton, and also Melissa Wilson, she is assistant professor in manure, nutrient management, and water quality from the University of Minnesota Department of Soil, Water, and Climate. Well, we all know that it's been a wet spring out there and obviously a lot of ponding and other complications and and dealing with, with with soybeans and soybean management.
Dave Nicolai:So before we proceed a little bit more, I think we'll turn it over to, Bruce and talk a little bit about some of these soybeans out there. Bruce, you know, I've noticed, you know, obviously there's variability in your corn, but I think we've got variability in soybeans as well. You know, this time of the year, we oftentimes run into crops that don't look very good, maybe a little bit on the yellow side, aren't as thrifty, there might be some field history here as well. What are some things that come to mind especially at this time of the year, I guess Bruce, in terms of of, making sure that we understand are we dealing with iron chlorosis? Are we dealing with soybean cyst nematode?
Dave Nicolai:You know, some of these other hidden things that don't show up, you know, right away until maybe this time of the year.
Bruce Potter:Thanks for having me, Dave. I think I think the issue here we've got this year that makes a little more tough is we've got so much water and we've got some water stress on these soybeans and we've got issues with just soybeans, just plain drowning. We've got issues with, root disease, we've got, we're starting to see some more issues with SCN and I think the trick right now is when you're looking at these fields is kind of try to prioritize exactly what's the, what's the, main, main reason you've got an issue out there. We've got some fields here where, you know, even from the road, it looks different and you go out there and it's because we've got a lot of missing plants, combination of disease and and, combination of just plain too much water in soybean plants. They do, they can drown and that's what happened in some cases.
Bruce Potter:We've had a lot of unusual amount of root disease this year because of the wet weather. And right now we're starting to see some soybeans that are yellowing up. It's a late season yellowing. Typically if you've got an iron chlorosis issue or IDC problem that happens early in the year. If we see yellowing beans right now, there's 2 things that, I I suspect.
Bruce Potter:One of those is, SCN and related to SCN, they don't have to occur together, but often they do. There's some diseases, things like, pod and stem blight, top dieback is, is one of the disease and that, that happens. You will see that more and more as the season progresses, the beans may green up again and then they'll, they'll, yellow up again if we get a new flush in nematodes or, new new infections.
Dave Nicolai:You know when, folks go out to the field and, you know, when it dries out enough, they can get back out in the field and walk around. What are some, scouting techniques that you found to be successful? So if they're gonna be looking for, perhaps the presence of SCN or maybe interested in in samples for for egg counts, how do they differentiate what they're looking at so they're not just looking at, soybean, you know, nodules, so to speak? Is there something there with that and the naked eye or a good hand lens? What what's helpful?
Bruce Potter:Well, sure. Hand lens always helps, and I think the the the difference between SCN, female SCNs on the SCN, on the outside of the roots and, and nodules is, the SCN are smooth, they're small, they're lemon shaped. The nodules are going to be larger, tend to be a lot larger and irregular shaped. So there's a shape difference. The FCN go through, there's more than 1 generation a year and that's one of the things you have to be careful about.
Bruce Potter:You could be out there even though it's heavily infested and at that time you get out there, we don't have females on the outside of the roots. They're they're, eggs or they're they're larvae inside the roots. Yeah. It matures inside the roots. I think the first thing to do is is is if you suspect SCN, you've got some plants that are stunted, or yellow and stunted, they don't have necessarily have to be be yellow.
Bruce Potter:Just dig dig or pull up some roots as long as you can get a good chunk of the root system and look at those roots for for SCN. If you see them, you know, that's females on those roots, that's an indication that there's reproduction going on. Particularly if, if you've got, if you're worried about, your SCN resistance in that variety not performing as well as it should. If you start seeing a lot of SCN on, an 88788 variety or or, we can even it can even happen now on, peking varieties. That's a clue that something's got to change in your management.
Bruce Potter:If you still suspect nematodes and you don't see any, you've got an option to just come back in a in a, you know, couple weeks, see if you see more nematodes on the outside then or take a soil sample. And, there's a lot of instructions on, U of M website in in the link there on how to take soil samples. But I think the the big caution is if you've got a bunch of dead plants, don't take that sample just in that horrible area. Take it on, a little bit to the edge and make sure you get some samples where there's enough root system left to to support the SEM.
Dave Nicolai:Well, we're, we're here getting to the last week in July next week. Traditionally, has this been a good time to really start that, or would you go early August? And and the other question is, all this wet weather, that we've had, is that gonna complicate some of this analysis or the survivability of the nematodes?
Bruce Potter:Well, it's the they're they don't they don't mind wet weather at all. In fact, that's how they get through the soil is they the larvae swim. So the wet weather isn't gonna bother and they're not gonna drown. The thing that's complicating is that, if you've got a lot of wet weather, it's an excellent question, Dave, because if you have good soil moisture, you're less likely to see dramatic symptoms and the simple reason for that is most soybean plants don't need as good a root system, to take up water because, you know, it's it's easily available. If you've got drier conditions, you know, then the the effect of that, SASN injury on those roots is is is more pronounced.
Dave Nicolai:Well, I know the, the nearby forecast indicates some warmer than average temperatures than we have been having. It seems like it's gonna be a little bit drier unless it really changes. So I would surmise that, you know, the 1st 2 weeks like we normally get sometimes here, could be drier. And so what you're saying is, you know, that that first, second week in August are still gonna be prime times. Correct?
Bruce Potter:Oh, yeah. Yeah. And I think and I think it's gonna be the case for not just SCN, but a lot of the root diseases is as those plants have a harder time getting to water, you're gonna see the impaired root system show up more. Any,
Dave Nicolai:any thoughts on any other diseases that might be appearing? I know we've been talking about Phytophthora on, different segments and and different things that we've done here in extension, and taking and looking out there. But I'm certainly that's, phytophthora is not just an early spring disease. It can show up later in the later in the year here. We have a plant disease clinic, on campus that can help with some of those situations, so that that might be helpful.
Dave Nicolai:I don't know if you've had any other observations or has it been more of a situation would you say just in terms of excess moisture for a lot of these soybeans at this point?
Bruce Potter:Well, there's definitely disease out there. I mean, and it kind it kind of if you've got moisture, it kind of depends on what your temperature is as far as which diseases are going to take the most advantage of that environment. But we've got even in spite of being wet, and, and not that cool earlier, we saw quite a bit of Rhizoctonia out there, pythium early on, Phytophthora. I think what we're gonna you know, I don't know this, but I sure suspect the way the weather we've had earlier, the hot weather is going to slow it down a little bit, but I would be surprised if we didn't see quite a bit of white mold this year. And, reasonably certain that we had some, pretty significant SDS infections early on, and those symptoms will show up more if it's hot and dry also.
Dave Nicolai:Let's let's go back to SCN or soybean cyst nematode for a little bit. Let's say, for example, you have an opportunity to take a soil sample and, I don't know how often, you know, people are going to do that in a situation, a particular field, sometimes frequently, sometimes not you know, many, many years will go by, but, sometimes these numbers are fairly low. Sometimes these numbers are really high. Is there any thought that you might have one over the other? I don't know necessarily if we pinned a number of a 1500 or 2,000 depending upon, you know, cubic centimeter of soil, but, or you will you literally look more about the presence of high numbers over time?
Bruce Potter:Well, I think what you're what you're, the first thing is is detecting an issue. And we in in Southern Minnesota, particularly, we could pretty much assume that there's SCN at some level in in most, if not all fields. What we're trying to avoid is these real high populations and particularly where we're using, resistant varieties. If we start picking up big numbers in a soil sample, and you planted the resistant variety, either that variety doesn't have good resistance or the nematodes have, in that field have evolved to be able to to reproduce just fine on it. And there then both cases are true.
Bruce Potter:We see we some see a lot of both. So I think that's the that's the big reason you're sampling is to find out if your is still working and if you're starting to see a lot of, SCN on a good resistant variety, you probably need to change sources of resistance and, you know, maybe use peking. You don't want to use that too often, but, throw peking variety into that rotation to kinda help slow that, resistance development down or or combat it a little bit.
Dave Nicolai:If you're, say for example, staying with one particular supplier, one one seed company, and maybe there isn't a limited amount of of peaking, but, you know, it's some of the other 88788 and so forth. Is it still good to rotate amongst that? Because not everything is identical. Correct?
Bruce Potter:Oh, yeah. Definitely. I mean and and I think this is where a lot of guys get in trouble is they'll plant, an SCN variety and they'll buy it from 3 different companies. Let's say they're all a group, 22 and they look their agronomics are similar. It's really possible you could have the same variety in in different colored seed bags.
Bruce Potter:So make sure you're actually rotating, 88, 7, 8, 8 varieties, not just planting the same thing out of a different bag.
Dave Nicolai:Yes. Or even if you're staying in the same company, rotate around a little bit as well.
Bruce Potter:Yep. Yep. Within a company.
Dave Nicolai:In there. Any last, thoughts here on soybeans? I don't know. We've got just a minute or 2 left here. We we didn't really touch touch on it, but, we'll be looking at, you know, corn, whipworm, and some other things that we'll be talking about that later.
Dave Nicolai:But any last, things that you wanted to cover?
Bruce Potter:Well, I mean, I'm I'm tend to focus more on the insects. And I think right now in soybeans, it's important to peep for people to to make sure they they're out there starting to evaluate, soybean aphid populations. Those are gonna ramp up as the soybeans, go through the R3 and early R4 stages, happens every year about this time and, and we'll see some pretty, we can see some pretty rapid population increases. I'm kinda starting to see that in a few fields right now. I talked to a consultant over your part of the world that was evidently practice spraying soybean aphids just so he knew how to make a recommendation.
Bruce Potter:I don't know. But, but, you know, I definitely definitely use the thresholds because just because you see aphids out there, or just because you see at least little isolated hotspots out there, there's no reason to to treat a whole field.
Dave Nicolai:Yeah. We're still at what? 2.50 per plant, 80% of the plants in the field? Yep. Yep.
Dave Nicolai:Okay. Hasn't changed there. And if they people have questions, we didn't cover here. There's a number of articles, Minnesota Crop News.
Bruce Potter:Yep. And there's a link, link to a whole bunch of soybean aphid information on the web and also SCN information.
Dave Nicolai:Okay. Great. Well, thank you, Bruce. We're gonna switch over here and bring in, Melissa. Melissa is our assistant professor in in the department of soil and and Water Quality here at the University of Minnesota.
Dave Nicolai:Melissa, we, we've had kind of a tough year, I mean, given the fact of getting into the field, people got their nitrogen down perhaps last fall, this spring. Now there are different sources, obviously, commercial fertilizer, but in in the case of things that you're working with, and that is in terms of, the proper management and timing of livestock manure, with that, you know, and sometimes when we have wet weather, Melissa, we have wet weather all the way down. It doesn't make any difference, but if it's if it's converted and if it's in the in the in the nitrate format, so forth, that could be there. But what's your observations and and kinds of calls that you've been getting in here? And in terms of that, in manure management timing and then and also looking forward to what should we think about this fall?
Dave Nicolai:I mean, some of the small grains are gonna come off. There's gonna be an opportunity for applications here, but, you know, the summer's not over. So the floor is yours.
Melissa Wilson:Yeah. Well, with the wet weather, we've been seeing a lot of variability across the fields, whether it's fertilizer or manure, especially in those low areas, the corn is looking fairly yellow. A lot of that is due to kind of what you talked about, nitrates in can change different forms in the soil or nitrogen can change forms in the soil, nitrate being one of them. And nitrates the one that we kind of don't necessarily want it to be in mostly because it can move with rainwater and it's been a very rainy year. So with warm conditions, the microbes in the soil are kind of kicked into overdrive that convert that nitrogen from organic forms if it's manure, ammonium forms if it's fertilizer or manure, and gets it into that nitrate form pretty rapidly within, you know, days to weeks.
Melissa Wilson:And then when you have all these rain conditions that are kind of driving water further and further down into the soil profile, that's when we're seeing our nitrogen losses. The other thing that we can see with nitrate is it can turn into a gas, and that's another microbial process. So when you get really saturated soils, like in the low spots of your field, unfortunately, the way that some of the microbes get oxygen is actually from nitrate because it's not getting oxygen, you know, from the air mixing in anymore. So it pulls the oxygen from that nitrate and the nitrate the nitrogen part then turns back into a gas and can be lost. So there's kind of those 2 competing things going on with these wet conditions.
Melissa Wilson:And that's why we see a lot of these nitrogen losses and why we see variability across the field because low spots are gonna obviously have those saturated conditions, but you can even have, you know, in your heavy soils that might be in one spot of your field, but not another. We can see some of that happening too. The difference between manure and commercial fertilizer is that commercial fertilizer is usually in the ammonium form or the nitrate form already, or it's in urea, which changes very quickly to ammonium. So with manure, it's a little bit of a different story and it depends on the manure that you're working with. Something like finishing swine barn manure actually has a lot of the nitrogen already in the ammonium form.
Melissa Wilson:Some of our data from manure testing labs here in the state shows us that it can be anywhere from 70 to 80%. I've even seen some up in the 90 percentiles where most of the nitrogen is in that ammonium form already. So it's already acting pretty much exactly like a commercial fertilizer would. But in other cases, like a dairy manure or a beef manure that might be stored as a liquid, it might be more like 5050. So it does take longer to break down that nitrogen to get it into the nitrogen form.
Melissa Wilson:So in some years, that can be really beneficial because that means that it's kind of more of a slow release nitrogen. Unfortunately, this year we had a lot of manure go on in the fall and then it was a really warm winter. So we're seeing a lot of variability in our manure fields. And I have some comparisons directly comparing fall manure applied to spring fertilizer this year down in LaSica. And for the 1st 2 years, manure outperformed fertilizer in both of those years that we did that.
Melissa Wilson:But the past 2 years, it's almost switched. Down in Waseca last year, they had that really wet spring. So the manure that had been applied in the fall, unfortunately, you know, had some of that had converted to nitrate, and then we lost that nitrate in those that wet spring. I think it was, like, May had an insane amount of water.
Dave Nicolai:So you mentioned outperformed. Can you define when you say outperformed in terms of loss or yield, but what's your definition of performance here?
Melissa Wilson:Great question. Yes. In that case, we had higher yields where we had manure in for the kind of first two years where we were doing some of these comparisons. But the last 2 years, because of the weather conditions, we're looking to have lower yields in our manure fields when we have the fall applied the manure.
Dave Nicolai:So the weather conditions that are when you're at a disadvantage are, what, wetter than normal in in situations with that?
Melissa Wilson:Situations where you can can like, where the fall applied nutrients can convert to nitrate. So warm winters, wet springs, those sorts of things.
Dave Nicolai:Yeah. Well, we're it's obviously we're warmer now. We didn't have really any much over 90 degrees this summer so far. We've touched it a little bit, and here and there in places with that. Thinking ahead here to this late summer and fall as we remove, you know, maybe a small grain crop or other types of things, it might be a canning crop in some places, but it opens up an opportunity for, manure applications.
Dave Nicolai:Some of this could occur in the month of August, some in September. Any management considerations here, all for maybe not only, you know, swine manure, but, I've I've seen, you know, everything from turkey litter to you name it piled up on the edge of the field. But, what about that time of the year here when we're not really into what I call the true cold fall?
Melissa Wilson:Yeah. So we always recommend putting on fall applying manure if you're going to do it. Get it on when the soil temperatures are cool just because of everything I've just been talking about. You put it on in August when it's still warm and September when it's still warm, you're risking conversion to nitrate and then you're risking loss. So if you are putting it on and you're growing something afterwards, like, we've had pretty good success growing like hybrid rye where we've, put on manure pretty early in August or September and then applied or then planted hybrid rye.
Melissa Wilson:And that looked really good going into the fall. It looked better than where we didn't have any nutrients. Or we're gonna spring apply the nutrients then. So getting roots in the ground, if you're going to put manure on that early, it's gonna be important just to make sure we're not losing the value of that nitrogen, particularly with fertilizer prices so high. Right?
Dave Nicolai:Like, we're
Melissa Wilson:We wanna get the best value we can out of it. So making sure that we're capturing those nutrients and keeping them up in the soil rather than in our groundwater is important.
Dave Nicolai:You know, with with swine manure, oftentimes you see in in the fall or the late summer the opportunity, you know, with large hoses and injection and so forth. Is that even in, the month of August September, you know, that injection still is, you know, a good alternative to, at least consider here, isn't it, versus just trying to, leave a surface supply?
Melissa Wilson:Yeah. And surface application, what happens there is the ammonium can actually turn into a gas. So that one usually sticks in the soil, but if it's on the surface, it can can turn into a gas. So making sure it gets into the soil is important, especially with something like a swine manure because it does have a lot of ammonium to begin with. And, like, that's one of the reasons it's there's a bunch of things that actually cause odor in manure, but ammonium is one of them.
Melissa Wilson:So if you can smell it, that means you're losing nutrients.
Dave Nicolai:You know, if if if you have an idea of what you normally do or need for from a fertility standpoint and you might use our nitrogen calculator that's online, other other sources, or, have a soil test for for p and k. But if you want to take a look at your analysis of, what have you found over the years? I mean, we have we've had tables that are general in nature and talk about nutrient content at various manures and and moisture levels. But is it still really good to, you know, take the opportunity to to get an analysis on your on your own on your own manure or your neighbors here?
Melissa Wilson:Yeah. Absolutely. One of the things that we've been finding we've been working with a lot of the local labs and actually have a project where we're working with nationally a lot of different labs, and we're able to look at track these changes over time. And one of the big things we've learned is that there's so much variability, even within Minnesota, there's so much variability. Swine manure is not an average swine manure.
Melissa Wilson:Like it's always, it can be off by 20, £30 of nitrogen per 1,000 gallons. And that's a big deal when we're considering, you know, our fertilizer bill. Right? Like if
Dave Nicolai:you're applying
Melissa Wilson:£40 per 1,000 gallons, but you're actually only applying 30. That's, you know, a pretty big deal when you're applying 4 or 5, 6000 gallons. So getting it tested is critical. And the big things are if you're, like, have a really consistent bar and you're not changing your feed, you might be able to get away with doing the 1st 3 years of an analysis in a new barn, and then you could do it for a couple of years after that, particularly if you're not changing anything. But if you're changing anything, you're adding different feed, you have different waters, you notice you're using a lot more water because it's warm.
Melissa Wilson:You know, things can potentially change in that manure. So getting it tested fairly regularly every couple of years is definitely recommended if you're changing things often and maybe even annually.
Dave Nicolai:So, the same thing if if it isn't manure that you're producing obviously on your own farmstead, but it's from a neighbor or a source. Like I mentioned before about the, you know, the poultry and used to be the the turkey aspect and so forth. It's it's good to do your due diligence there as well, isn't it?
Melissa Wilson:Yeah. Absolutely. One of the things you'll definitely wanna get from them is a manure nutrient analysis so that you know, what kind of nutrients they're applying. Make sure you're getting, application records. So hopefully, like, how much they applied and where they applied it.
Melissa Wilson:So that way, if for some reason a corner was missed or something, you can go back in and make sure to hit that with commercial fertilizer. And, kinda think about your fertility too. Do you want them to apply, like, you know, there's a lot of variability in the field. So do you want them to apply a lower rate and then come back in and side dress nitrogen? We've been recommending that because it takes off some of the variability that we see with manure from year to year.
Melissa Wilson:But you can consider applying like a base phosphorus rate for instance, so that you're applying your phosphorus needs for the plant and then coming back and adding the rest of the nitrogen that you missed, for instance. But there's all kinds of things to do. Just make sure to consider what you wanna do for your fertility plan and then kind of plan around that.
Dave Nicolai:Well, I would imagine in some places, some folks might be taking a deep nitrate test or other, pre side rise and nitrate test. I mean, you would still recommend that to help, what, fine tune that, so to speak?
Melissa Wilson:Yeah. So one of the things that's interesting about Minnesota is a lot of the work on the PSNT, pre side dress nitrate test, has been done on nonmanured fields. We're actually just started some research projects. I think we've just finished up a full year. We're halfway into the 2nd year looking at doing pre side dress nitrate test in a manure field from the previous fall.
Melissa Wilson:So there might be manure fields that have done it, but it's like wasn't when manure was applied the previous year. It was like a couple years ago. So we're trying to see if that is useful, and then we can make recommendations based on it. A lot of the other states actually only use the preside dose nitrate test in manure fields, at least when I worked in Maryland on the East Coast, a lot of them were using that only in Menard fields. So it theoretically should work pretty well, but we're trying to build some data on that to just make sure that it's making and matching up in our midwestern soils.
Dave Nicolai:Any, look at this fall, okay, past August, any final words about application? I know you you mentioned a little bit about soil temperature and so forth, compaction. Anything else that you want to mention about good best management practices for what I would call a true fall application here?
Melissa Wilson:Yeah. Definitely, the later you can get it on or closer to the soil temperatures reaching that 50 degrees, the better. And that's not necessarily a hard line. Like, getting it on at 60 degrees is better than getting on at 70 degrees, which is better than getting on at 80 degrees and so on and so forth. So trying to aim for that is always good.
Melissa Wilson:If you need to get it on a little bit early and it's something like a swine manure, which has high ammonium, and it's only a few weeks earlier, we have seen some success using a nitrification inhibitor in the manure, but those only last for a few weeks. So if you're talking about putting it on in August or early September, that's it's not gonna make it the rest of the way into the fall because it like everything else is subject to microbial action in the soil. And if it's warm and wet, it's gonna break down faster.
Dave Nicolai:Okay. Great. Great. Well, any other last, last comments here at at this point in time? If if people do have questions, perhaps where they wanna learn a little bit more, you you've had various publications, through, Crop News.
Dave Nicolai:If they have to look at some standard analysis, you know, what I call the old checkbook method of, you know, like I've got this manure, this type of manure, nutrient, so forth. There are some different references for that. Again, not necessarily that accurate, but at least a guidepost.
Melissa Wilson:Yeah. We have our website is menor.umn.edu for general guidance. We also just started a project. I was talking about working with National Labs, and you can actually access all of that data. It's our we call it Menor DB, DB standing for database.
Melissa Wilson:So that's menordb.umn.edu. And you can pick, like, Minnesota, what kind of species you wanna look at, that sort of thing. And that'll show you some of the averages and medians and stuff like that.
Dave Nicolai:Okay. Well, great. Well, thank you, Melissa. We appreciate that, that information. We wanna thank again, our hosts, in terms of our guests, today, Bruce Potter and, from the Southwest Experiment Station and Research Outreach Center at Lamberton and Melissa from the Department of Soil and Water and Climate, to be with us here today on this field notes program.
Dave Nicolai:Also, we want to thank our sponsors again the Minnesota Soybean Research and Promotion Council along with the Minnesota Corn Research and Promotion Council.
