Weeds AR Wild Series, Season 2 Episode 8. 
Title: Weeds AR Wild Series, S2 Ep8. Soybean Weed Control Tips: Planting Early and Residuals
Date:  April 7, 2022

[Music]:  Arkansas Row Crops Radio providing up to date information and timely recommendations on row crop production in Arkansas.

Tommy: Welcome to the Weeds AR Wild podcast series as a part of Arkansas Row Crops Radio. My name is Tommy Butts, Extension Weed Scientist with the University of Arkansas System, Division of Agriculture. Thanks for joining us today. I actually have Dr. Jeremy Ross joining me here, our Extension Soybean Agronomist. Jeremy, you want to say “hi?”

Jeremy: Hey, appreciate the time and thanks for having me on, Tommy.

Tommy: No worries, Jeremy. I mean, I guess I have to have you on eventually for some of this.

Jeremy: [laughter] Yeah. There is a few soybeans in the state. So, we try to get information out on soybeans any time we can.

Tommy: So today we wanted to hit on just a few things. You know, right now we're recording this. It’s the first week in April. And what we really mainly wanted to touch on was some soybean weed control tips for the year. Particularly, planting early. Here, if we can get out, if the rain stops and we have a chance to get out and plant early here. And then using those residual programs and what we need to do on that front. So that's kind of what we're going to hit on today. But the first thing that we really wanted to mention, before we even dug down into that, is with the year that we're having and the prices fluctuating fertilizer prices going up and down, the market volatility, all those kinds of things, herbicide availability being low and prices high. There's going to be a lot of moving parts this year, it appears. And so we just wanted to reemphasize to everybody, make sure that we're keeping good records this year. Know what's planted where. Know what technologies we have out there, what herbicides we have in our spray tank, what we're mixing, all those kinds of things. Pay close attention this year, because there's just a lot of those moving parts. And we don't want to have those incidences where we have one technology that we thought was planted there and we spray it and well, we found out we had the opposite technology there and things like that. Also just make sure to know all your trait packages. So not even just the normal ones like Enlist versus Xtend or XtendFlex. But also know if you have an STS BOLT bean or not and whether you could spray a Permit, Permit Plus over the top or if you're spraying nearby, what drift might do to some of those. Those kinds of things. Just make sure you have all those traits locked down and you're keeping good records so you can go back and remember exactly what's where. If you're ever unsure about what the trait technologies are and what herbicide tolerances they actually possess – because, we have a whole lot in the soybean world now, with like I mentioned in the Enlist, the Liberties of the world, Xtend, XtendFlex, all of those. Make sure to check out our MP544 publication, the Herbicide Resistance Traits Quick Reference Guide, and that'll give you a quick rundown on which traits are resistant to which herbicides, and that'll help you out on that front. But Jeremy, do you have anything to add on the record keeping front for this year?

Jeremy: Yeah. So, Tommy mentioned every year I get calls from at least two or three farmers saying that “the tractor driver got in the wrong field and either they got in a hurry and didn’t write down what technology was in which field” or, “one field was wet, and so they switched to a field and never did get it recorded.” So, I mean, that's pretty important to make sure you get that. And especially, as Tommy mentioned, this year with the prices and everything kind of in short supply. We need to do everything we can to make sure everything gets done correctly the first time. Flag the Technology, you know, we had that program. It’s still around and you can still get the flags. I know a lot of people, especially the tractor drivers, when those flags are sitting at the entry of a field, they can at least stop and maybe pause and think, “hey, that's that color flag and that represents, Dicamba or Enlist or conventional or whatever.” And then maybe it’ll just give them a little bit of pause to double check exactly what they got in the tank, and which field they’re in. And so just want to kind of give a quick plug for the Flag the Technology program.

Tommy: And with that, there's also the DriftWatch online technology, too. And so if you don't use a flag, but you want to use the online technology that's also out there to know what's where, and you can put in the different technologies into that system as well. So moving on from the recordkeeping. We don't want to spend too much time on that. Let's just jump right into discussing early planted soybean and some of these cool or wet conditions that we might be putting some of these soybean plants into. So to start off, I just kind of wanted to give it over to Jeremy to let him talk about some of the potential agronomic tips or concerns that early planted soybean may entail for us.

Jeremy: Sure. So, you know, I've covered most of these at the winter meetings the last few months, but just want to kind of reiterate some of the main things we need to kind of keep in touch with, you know, keep in mind when we're looking at some of these early plantings. So, the last couple of years we struggled trying to get our soybean crop planted early. It seems like we're kind of in that same pattern as we were last year, getting rainfall about every five to seven days. And, we may be able to get one or two days a week. And that's going to be a struggle. But hopefully we can kind of break out of this weather pattern and then really get some fields prepared and get some beans planted here in the next few weeks. But first thing is planting dates. You know, for southern Arkansas, that's going to be the 1st of April to the middle of April, is where we can maximize yield. Once we get past the middle of April in southern Arkansas, we're looking at a 2% decline there at the end of April. So, I mean, it's not a huge decline, but the more beans we can get planted in southern Arkansas the 1st of April, we can take advantage of that maximum yield potential. As we move further north, we get to the northeast corner of the state. That optimum planting time is going to be the 1st of May till about the middle of May. And so, everybody always asks, “Well what about central Arkansas?” Well, it's going to kind of fall in between those two times. So, for the central part of the state, kind of the I-40 corridor, the optimum time – you know, we're looking the middle of April to the middle of May trying to get those beans planted.

Tommy: So, Jeremy, you mentioned the optimum window there. Let's say, a grower in northeast Arkansas wants to plant the beginning of April versus the beginning of May. What's that look like for the yield potential front, yield penalty front, that kind of thing?

Jeremy: So, going earlier, you're only looking at less than 2 to 3% reduction from the optimum.  We've got the study that I'm referring to, was conducted by Dr. Larry Purcell as a regional project. And we had a couple of sites here in the state. And so even if a producer in northeast Arkansas planted the 1st of April, you're only looking at a 2% reduction compared to the optimum time. So if you look at the planting window, there's less yield potential, or less yield penalty going early or before the optimum time versus waiting until late in the season and planting after the optimum time. So you know, I've had a lot of people this winter ask me, “what, is too early?” We actually had, you know, a field planted the 18th of February. It took it about a month to come up. But they did get a decent stand and they got about 125,000 plants up. They struggled, went through a couple of cold snaps and cool the wet conditions. But it's going to be interesting to follow that field for the rest of the year. But, if I was growing soybeans and had quite a bit of acreage to go, I would shy on that. Try to get as much planted on the early side. And then hopefully most of it is going to fall in that optimum category and then have less on the past optimum time later in the season.

Tommy: One more quick question, too. You mentioned that slight penalty for planting a little bit earlier. Was that for like an equivalent maturity group or can you play maturity group games and maybe, you know, get a little longer bean? What's the best case scenario there?

Jeremy: Yeah, so you jumped ahead and, I was going to mention that. [laughter]

Tommy: Sorry. I’ve just got good questions, Jeremy. [laughter]

Jeremy: You know, great minds think alike. So, the study that Dr. Purcell did, they looked at 3s, 4s, 5s, and 6s. And what really surprises coming out of that, is that we need to be planting our Group 5s the same time we're planting our Group 4s early in the season. To optimize Group 4s and Group 5s, we need to be in southern Arkansas the 1st of April and then northern Arkansas the 1st of May. Once we get past that optimum time, the yield potential is greater with our Group 4s planted even late than it is with our Group 5s, which is totally the opposite of what we've been saying the last 20, 25, 30 years. 20 years ago we always said we need to plan our Group 5s late in the season, they withstand our droughty conditions, hot conditions, better planted late. But from the data coming out of this study that was done a few years ago, Group 4’s maintained their yield above the other maturity groups. So, I think a lot of farmers have shifted. The majority of our varieties that are planted are Group 4s. We still have some plant Group 5s, and mainly because they’re looking for certain characteristics other than maturity group. They're looking for nematode resistance or there's some other characteristics of those varieties that perform well on those fields than a Group 4 does. But, on the maturity group side, I would stick with the 4s as long as I could. So, talking about seeding rates, done a lot of work on seeding rates this year. Everybody's looking for areas where they may be able to save a little money. If you've historically been in the 140-150,000 seed per acre range on your seeding rates, you may be able to cut of 10-20,000. Our data is showing that with seed treatments we can start to maximize yield around 100,000 seed per acre. And then if you go with untreated seed, you need to bump that up to about 125,000. And in some of those studies we went all the way to 200,000 seed per acre. And so, our yield really didn't change that much from 100,000 to 200,000 with treated seed. But, again you might be able to shave a little bit off of that. Really what we're trying to do is get a minimum of 75,000 plants per acre to maximize yield. Things are going to change, you know the germ and the vigor is going to change, planting conditions are going to change. You know your farm, you know how varieties have emerged in the past. Hopefully, you don't cut it too much because, we get quite a bit of yield penalty once we get below that 75,000 plants per acre. But it's really hard for me to tell you exactly what seeding rate you need to plant. So still plant a little bit more than, probably more than 100,000 – because if you plant it right at 100,000, you've got to make sure that pretty much everything comes up during that time. Seed treatments, again, this year we're probably going to get one shot at trying to get things planted. And so seed treatments are going to be real helpful on making sure you get a good emergence. We see benefits with seed treatments especially planted early in the conditions that we have today – cool wet conditions. And, then conditions late in the season, kind of that optimum time where we have, perfect conditions and soil moisture, and the plants are emerging within five days after being planted. We typically don't see the impact with the seed treatments during that time as we do on the extremes of the planting window. Probably the next biggest thing is soil depth. We need to be planting inch and a half, two inches. I know once we get late in the season and we start losing soil moisture, farmers chase that soil moisture, and you're going three or four inches deep. It's just real hard for soybeans to emerge once you really get four or five inches deep. And so just be sure you're planting the proper depth and you have really good seed to soil contact. Especially in No-Till or you're planting into a cover crop condition. We need to make sure that we got really good seed to soil contact and we're closing up that furrow, so we're not drying out those seed that we’re planting. And then the last thing on this early planted, a lot of questions on inoculants. We don't see much of a yield benefit with inoculants with these early planting conditions. But once we get out past the middle of May, we recommend looking at inoculants. Because we've got quite a bit of data that shows that we're seeing a yield benefit with the use of these inoculants planted after May 15th. I kind of, again, look at inoculants as cheap insurance. I'd rather spend 3.50 to $5 on an inoculant versus having to come back with 300 pounds of urea if you happen to have a problem and you don't get good nodulation. There's probably some other things, but that's kind of the top five or six things we need to be thinking about, especially in this early planted window and trying to get a good soybean emergence. 

Tommy: Thanks Jeremy, for all those tips. I think those are really good things to consider. And on the weed control front, I just want to hit on a couple things and I've talked a lot about early planted crops in the winter production meetings as well as couple of weeks ago when I did the Rice podcast with Jarrod, talking about residual programs and things. So, I'm not going to hit on some of these things a lot. But I just wanted to reiterate, with early planted soybean it gives us a little bit of a higher likelihood for residual activation, which helps out our weed control programs. We just have more moisture in the month of March and April than we do once we start getting to June. So that can help us out. We also typically see some extended length of residual activity, which is also a real positive thing. And we might get three to four weeks out of it as opposed to one to two, two and a half weeks kind of thing out of some of our residuals. And that can also be a little bit of a downside because we may have some more potential for injury. But most of the time that injury from our residual applications are just kind of superficial or minor, and we just got to walk away for a week or two and let them grow out of it. And the weed control we get out of it, it trumps having to see that injury for just a little bit.

Jeremy: So I have walked several fields in the past where you get a rainfall at the wrong time. And, some of these residual herbicides do get on the plants and actually bang them up pretty good. But, from the hundreds or maybe thousands of fields I've walked in my career, I mean, I think I've only recommended maybe a replant of one or maybe two fields during my career from injury from residuals. I mean, is that kind of what you've been seeing? I mean, I usually tell a farmer, like you said, “walk away from it for seven to ten days and come back and look at it.” And usually you have some new growth and it'll look totally different than it does after a splashing rainfall or something like that.

Tommy: Yeah, about the only time I really see where you have like severe, severe injury that I might be a little concerned about with a PRE is either if you didn't get a good furrow closure and you get some of those that get right down in there on the seed, wash down right in on the seed, or like you said, if you're at like cotyledon stage and you get this big splash event, you splash a whole bunch on it. But again, very – to me, very rare occurrences there. And the other injury that pops up, it just it looks bad for a little bit and let it grow out of it after a week or two. And the weed control part of that is going to be so much better…

Jeremy: Absolutely.

Tommy: …than not. The one other thing I wanted to mention was just to give you some insight on what weeds you might be battling out there, too, at different times of the year. So, I've done this with rice. We've talked about it, some other things. But I wanted to mention with soybeans, too, you know, when weeds typically emerge, which weed species typically emerge. So if we plant a little bit earlier than normal, we may move into some different weed spectrums. Some of our real early emerging weeds typically are the horseweed or marestail that we're dealing with out there. The Italian ryegrass, which everybody knows. Smartweeds and yellow nutsedge are both actually fairly early emergers, too. We're talking somewhere around 45-degree soil temps that those weeds I just mentioned will start to really germinate hard. So those we’re probably already starting to deal with maybe popping up in in bad areas. So be aware of that. A couple of weeds that are kind of in the middle are barnyardgrass and common cocklebur, that is making a comeback. I've been getting more calls on that. They generally kind of sit right in the middle, roughly like a 60-degree soil temp. So, they're not really early, but they're not really late. They just kind of are in the worst window. We're kind of battling them throughout the entire time we're trying to plant and grow. And then the other ones that are late emergers that we can generally get ahead of if we do plant early, are things like our Palmer pigweed, morningglories, prickly sida, or teaweed and even sicklepod. They're all generally late emergers. They like to have about an 80-degree soil temp and have some pretty big fluctuations over the diurnal cycle. And so if we can plant a little bit earlier, we can get a head start on a lot of those weeds and have that crop start to just have an advantage because it's out in front of some of those weeds that are normally a lot later. So just be aware of that or which weeds you might be battling when and if you have a real bad problem with one of those, maybe you can play a game with your planting date to help you out as well. Now, getting outside of early planted soybeans, unless you had anything else to add in that category.

Jeremy: No, I’m good.

Tommy: Okay. We wanted to hit on residual programs, setting ourselves up for success throughout the season. And the best way to do that, again, is use residuals. Get them activated because they always are going to give us the most consistent and economical weed control at the end of the year. So the main thing that I can tell you is my advice from residual programs, and this applies across trait technologies, whether we're talking Xtend, XtendFlex, Enlist, LibertyLink, even conventional. Right? This applies across all of them. The best thing I can tell you is get multiple modes of action out there. They're needed. And I always steal Tom Barber's comment of “two is better than one and three is better than two.” The more modes of action we can get out there and tank mix or use in a premix, the better. In a lot of my small plot research, things like Trivence, Fierce, Boundary, even the new Tendovo product that's out from Syngenta, all of those are multiple modes of action in those mixes. They're all really good products that get us exceptional weed control and pretty good length of residual control as well. And not only are all of those that I just mentioned good for pigweeds, because pigweed is always our number one that we're typically targeting. They also provide us some broad-spectrum control because of the herbicides that are in there. So, they can knock out things like yellow nutsedge or things like morningglories or things like grasses or the prickly sida/teaweed problems that are occurring. The broad-spectrum of control from those is really good. And so it just helps us manage that diverse spectrum a little bit more as well, on top of just being really good pigweed material. And then because we have those multiple modes of action in there, it's helping us delay resistance. So I mean, there's three or four advantages to using these premixes or even if we want to do the tank mixes, just making sure we're getting multiple modes of action out there. Now, one of the most important herbicides that I'll tell you to get on almost all of our soybean acres probably is Metribuzin anymore. It's really important to us as a PRE. It helps - it aids us in pigweed control, it aids us in some other weeds as well. And it just helps us out on a lot of fronts. And it's just like I mentioned, it's one of those ones I would be throwing in as a mixed partner for just about every soybean PRE residual acre out there, unless you have pH concerns or varietal tolerance issues. And I was going to let Jeremy talk about that for a second.

Jeremy: Yeah. So a few weeks ago, me and Dr. Norsworthy did a podcast specifically on Metribuzin. And so if you want to learn a little bit more about that, you can pull up that podcast. We've tried to get as much information out to growers as we can. So, we've got the Metribuzin ratings in the soybean update that's available on the website. And also we've got a standalone Metribuzin document or publication that you can look at. And, I would highly recommend if you're using Metribuzin, to look at it and make sure that your variety is either in that slight to the moderate category because for some reason this year we had more varieties in the severe category or do not apply Metribuzin onto those varieties. Education is key. Just make sure you look and you know that your variety is going to be tolerant to the Metribuzin. And so they are, again, several different avenues to get that information. I have already had one producer call and he said he couldn't find the variety. If it's an older variety, he may need to call me or email me to pull out some of the older documents to try to find that information. Because, you know, some of the older varieties, the companies just don't put them in the variety testing every year. If they get enough data on it, they're not going to have it. So if you do have a variety, you can't find by all means, reach out to me and I'll see if I can find that information.

Tommy: Yeah. Thanks, Jeremy. Appreciate that info too. The last one that I wanted to mention too, because I've gotten a lot of questions on this, is the PPO-inhibitors, especially from a residual standpoint. Across the state, we pretty much assume a bulk of our Palmer pigweed populations are resistant to the PPO-inhibitors. But generally, we test that from a POST perspective, right? A postemergence option. When we do it, when we spray these PPO-inhibitors as a residual, we still actually see what I'll call decent levels of control out of some of those PPO-inhibitors from a residual standpoint. And what I mean by decent is, if we're in a PPO resistant area, but we spray something like Valor or the sulfentrazones of the world, the Authority and Broadaxe products, the fomesafen-Flexstar prefix products, that kind of stuff, we may still be able to get about a 60% residual activity. Now by itself, that's obviously not good. But again, if we're talking these mixtures, if you get 60% from that, you add Metribuzin to it, you had a Group 15 to it and you're talking that that 60% is actually adding quite a bit to that mixture. So I wouldn't say completely scrap those PPOs out of your toolbox, but I would say they need to be used very wisely. Make sure you're getting them in good mixtures and make sure you're not relying on them solely and those kinds of things, because they can still add a lot too, to other weed controls. The Flexstars of the world are still a really good option for morningglory control and things like that. So again, they still have a place in our toolbox, but we just need to use them a little bit more precisely, I guess would be my keyword there for that. Outside of the preemergence residual programs, then, as far as residuals go, we want to make sure that when we come back for our first postemergence application. Which I would generally say may be about three weeks after our PRE –  depending on when we plant and environmental conditions and things, but somewhere around that two-to-three-week window, maybe four weeks if we plant it early, that kind of thing. You want to make sure we're overlapping another residual at that point, with whatever POST products you're spraying. Just, again, help lengthen our residual control, especially if we're planted on wide rows. If we're on 38-inch rows or even 30’s, we need some extra residual out there to get us to that canopy closure. And so, at that point we want to overlap a Group 15 herbicide and whether that's Dual or Zidua or Outlook or any of those. We want to make sure to get those out there and overlap. The major thing is, just depending on the time of the year, make sure to kind of watch some of your plant-back windows there. But overall, that's our best way to make sure we can get to canopy closure with no weeds there. And not only do they help with pigweeds, the Group 15’s – they also help with our grass pressure out there and we've had a lot of grasses anymore that are giving us fits too. So that's our best way to really maintain weed control season long there. And again, overall just to reemphasize, we harp on residuals a lot but it's because a strong residual program aids our entire weed control package. It just does so much for us on a lot of ends and it's a lot more consistent than trying to battle everything from a POST perspective. So the more of those residuals that we can get out successfully, the more flexibility it's going to give us and the overall, better weed control we're going to get. And it may help us cut down on the need for multiple POST herbicide applications, or the need for huge tank mixes later on in the season. And if we can cut down on some of those big tank mixes late in the season, or even cut out an application later in the season, that may be very beneficial to us. Like in a year like this, where a lot of our POST products are either short on availability, high on prices, or maybe there might be a lot of people scrambling to try and get them if our soybean acres are up as much as they're kind of predicted in this year. So again, get your hands on those residuals and use them. They'll do a lot for us. So, Jeremy, did you have anything else to add on the on the weed control front and the residuals?

Jeremy: No, but, you mentioned up in acreage. The report that came out last week has us at 3.25. So that's up know almost 200,000 acres compared to last year. And so already with the short supply on some of these herbicides and other things that we're going to need to produce this crop, that's just another added component to this whole thing. So, we're going to have additional soybean acres. So again, just make sure you got your herbicides and your fertility, hopefully purchased and on-hand when you need to do this.

Tommy: And I'm sure those numbers aren't done fluctuating yet. I mean, we're still only talking in the first week in April.

Jeremy: Yeah. You know, and they always do. And it always depends on what the weather does. You know, if we continue in this rainy period, soybeans may be down – or soybeans may be up, if corn and cotton go down, or it's just still kind of a moving target right now.

Tommy: Well, excellent. With that, I just kind of wanted to leave y’all, again, with some different outreach things that you can get more information from us, if you want more info. Make sure to check out our website, www.uaex.uada.edu/weeds. We post a lot of our latest information on the website there, and you can track down our contact info and all that kind of stuff. Make sure to get your hands on our MP44 publication. You can either visit your local county extension office or download it online. If you haven’t, please sign up for our texting service. We're sending out updates through that, especially now in the busy season. We're adding a few more texts each week, but just gives you information right on your phone that you have on hand from us so you can use that or know what to be on the lookout for. Right? In a timely fashion. How to join that text service. You just need to text weeds to, and that's W-E-E-D-S to (501) 300-8883. If you want to join the soybean text list, you just text that same number and all you have to do is text SOYBEAN to that to that number. So you can join both of our lists just by texting those words to that number. And then finally, as always, if you ever have a question or you need some more information, please feel free to get a hold of either Jeremy or myself directly. You know, shoot us an email. Give us phone call, whatever you want to. Even send us a text and we'll be happy to help you out with whatever problem you might be facing. So we'll try to help, at least! [laughter] We try our best.

Jeremy: [laughter] We do the best we can.

Tommy: Yeah. With that, Jeremy, did you have any final comments?

Jeremy: No. Just the same website instead of weeds. So, it's forward slash soybeans. And so again, all the variety information and then a whole host of other information, for anything related to soybeans, can be found on our website. And then, of course, our county agents are a vital source of information. And so I'd reach out to them as well because they know a lot about soybean production. If they don't know, they'll contact one of us to try to help out.

Tommy: Perfect. And we both wanted to thank a few people. We wanted to thank the Arkansas Soybean Promotion Board for their funding and support  that goes towards and drives a lot of our soybean weed control recommendations from research that we conduct, and helps us provide Extension opportunities just like this podcast series. And on top of that too, some funding from the USDA has helped us do a lot of these things as well. So thank you both to the Arkansas Soybean Promotion Board and the USDA ARS Programs. And thank you, Jeremy, for joining me today and taking part in this podcast.

Jeremy: Well, thank you for letting me jump on to the weed podcast. [laughter]

Tommy: [laughter] No worries. Well, and again, thank you all for continuing to join us and listen to this podcast. If you ever have any questions, reach out to us. Or if you want to hear something specific on the podcast, let us know. Reach out to us and we'll see what we can do. So with that, I just wanted to say thanks for joining us for this episode of the Weeds AR Wild podcast series on Arkansas Row Crops Radio.

[Music]: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information, please contact your local county extension agent or visit uaex.uada.edu.