Title: Weeds AR Wild, Ep. 17: Late-Season Soybean (6/23/21)

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

Tom Barber: Welcome to the Weeds AR Wild podcast series as part of Arkansas Row Crops Radio. My name is Tom Barber and I'm an extension weed scientist with the University of Arkansas System Division of Agriculture. Today for episode 17 of the podcast, I've asked our esteemed extension soybean specialist, Dr. Jeremy Ross, to sit down with me and discuss the soybean crop and some of the questions that he's been getting on replant scenarios behind the flood. Jeremy, thanks for taking time this evening to visit with me and I know there are a lot of growers out there with some questions. 

Jeremy Ross: Yeah, I appreciate it Tom. We've really been focusing on the flood down in the SE corner of the state, but really a lot of the recommendations that I'm going to be talking about the next couple of minutes really pertains to any soybeans that are still being planted. When we're looking at these late planted soybeans compared to our normal planted soybeans, really what we're looking at is trying to get as much light interception as we can to try to produce the best crop that we can. Even though as we're delaying planting we're reducing our maximum yield. We can still do fairly well with late planted beans but there's just a few things we need to kind of think about when we're looking at these late planted beans. The first thing you want to look at is your row spacing. A lot of our data says that narrow rows increases yield, but definitely late planted scenarios we need to look at, drill spacing is probably less than thirty inches and so a lot of our farmers are trying to switch to rice drills and trying to get that seven and a half, ten inch row spacing, so that's the first thing I'd probably recommend. The next one is seeding rates. With the late planted crop we really need to increase our seeding rate. Number one is because our germ and accelerated agents starts to come into play and we just don't get the germination and the seed emergence that we typically do under normal conditions. The accelerated aging really comes into play under these really warm soil temperatures so we really need to make sure that we've got a good accelerated aging on the seed that we're planting. When you're looking at seeding rate, you need to increase your seeding rates ten to fifteen percent over your normal seeding rate, so if you're typically planting at about a hundred and fifty thousand you probably need to bump that fifteen thousand to twenty thousand just to get enough seed out there to get a light interception. Probably the biggest question I've had is what maturity groups do we need to plant? Our data is showing that group 4's still perform the best and have the best yield production. Really at this point we really need to be focusing on our mid 4's and kind of moving away from our late 4's, so I'm talking 4-3, 4-4, 4-5, maybe a 4-6, in that range. And the main reason is because we're kind of running out of time. I've had several calls in the last couple of days asking what is the latest we can plant soybeans and still get a yield? If we kind of look at it, July 15th is probably going to be about my extent. Once we get past that date we really start running a risk of hitting either a freeze or a frost especially as we delay planting. So if you look at the average frost date for Dumas Arkansas that's November 3rd. So if you look at average mid 4's it's going to take about a hundred seventeen to a hundred twenty days to get that crop to maturity from emergence. And if you add it up from July1st to the first of November, that's a hundred and twenty days so we really are starting to run the risk of not being able to harvest that crop because we may run the risk of a frost problem that late in the season. And then the next thing is looking at inoculants. We've got a whole host of data that's showing that late planted soybeans perform or have higher yields with the use of inoculants. If you look at our data, mid-June planted soybeans means we're averaging anywhere from five or six bushels with the use of inoculants and then if you look at mid planted or mid July planted soybeans that bumps it up to about ten to eleven bushels increase. And that's not to say we're seeing the same yields in July that we were for May planted beans. Progressively the yields have dropped down but we're seeing a really good benefit, a really good yield increase with just the use of inoculants. So Tom, what about herbicide options and herbicide technologies? I know we're kind of getting to the cutoff on some of our applications on herbicides but you might want to give us some insights on what guys need to look for on these herbicides.

Tom: Yeah, and that's kind of the biggest questions coming in to us as weed scientists and I know a lot of the questions in our meeting Monday night had to deal with is can we plant beans behind everything basically because we've got corn that's drowned out, we've got cotton drowned out. We've got those herbicides down in a lot of cases and in most cases it's been at least six weeks. Luckily between those residual herbicides and when we'll be able to plant beans so I feel pretty confident in getting a soybean stand behind most of these herbicides, most of our corn and cotton herbicides, you know Brake, a herbicide that we use in cotton probably hangs out a little bit longer in the soil than most of the others that we use in cotton or corn either one and so I'm a little concerned with Brake going to soybeans, but again we've had a lot of rain, close to twenty inches in spots and so I feel like that for the most part most of our herbicide has been either flushed down into the soil profile or washed out of the system or there's new dirt that's covered it. You know we talk about when rivers and streams get out, ditches get out, I mean we're moving a lot of soil, and sometimes we'll have another layer of top soil on top of what we had there already. For the most part we're recommending going ahead and replanting these soybeans. Brake is the one caution I would throw up. We may still have some issues behind Brake herbicide that's been applied in cotton but even there as long as long as we've had six, I'd rather have two months but as long as we've had six weeks I think we've got a pretty good chance. But there is some concern there. Moving forward Jeremy you talk about row spacing and narrowing those row spacing is really going to help on our weed control as well and the quicker we can get canopy the better off we're going to be, because fighting weeds in the middle of July is not fun with any herbicide. The weeds just don't respond as well in those hot dry conditions of July and August as a whole so we're recommending like you said, plant something that's tolerant to Glufosonate, it can be Enlist, XtendFlex or straight Liberty Link. That's going to give us more flexibility. I did have my first call today of not being able to find the Glufosonate they wanted and that was in a small area in north Arkansas. I don't know how easy it is to find right now. This is the first time that a grower has told me they absolutely couldn't get anymore. For the most part we've been able to get it, so if that's the case we're running up on June 30th here in seven days and so June 30th, Dicamba cutoff for the Federal label for soybean production and so really that lends back to the Enlist system I guess if we're not able to get Glufosoante. But we need something to be able to control these pigweeds in July and August because they will be coming and you may have more than you thought you had because they will wash out of the ditch. Some of these seeds can wash out of the ditch and be a problem in our fields. One thing I do want to touch on is Flexstar because we get a lot of questions about Flexstar now. Number one we have a lot of PPO resistance out in the state to Flexstar in our pigweed population. But the other thing is Flexstar has a ten month rotation to corn and grain sorghum and that's a real rotation that we need to be concerned about. Any of these late beans that are planted, if we use anything containing fomesafen herbicide, that's the active in FlexStar, then we need to be mindful and mark these fields to not go back to corn or grain sorghum likely the next year. And where we're going to see the biggest issues is where we overlap. But still we get calls every year about Flexstar carryover in corn and grain sorghum. 

Jeremy: Yeah and that's important and like you said I think with the flood and everything, I think these weeds are probably going to come back with a vengeance. I think it's going to be tough to control those. Just a last couple of points and really kind of focusing on insects and diseases. We still are recommending seed treatments. I've had that question the last couple of weeks with this flooding issue and late planted soybeans. We still see a benefit with insecticide, fungicide seed treatment. I know a lot of guys are looking at cutting costs but we definitely need to try to preserve the seed that we're planting now because we're just not going to have the option or the luxury of coming back and replanting those again. We're just going to completely run out of time so along with those fungicide and insecticide seed treatments, look at inoculants, just be aware that there are certain insecticide, fungicide that are not compatible with certain inoculants. Just look at the labels of the inoculants and make sure that the seed treatment you're looking at applying to the seed are labeled for that. And then the last thing, I know a lot of people aren't really thinking about it now but, is late season insect and disease control. A lot of these beans are going to be some of the last beans in the fields especially in southern Arkansas and so we typically have boll worms and stinkbugs to begin with even in our early planted beans, but these are just going to be kind of bio-magnets. These fields are just going to be havens for these late season pests and so we definitely need to be out there scouting in these fields and making sure we're getting on the proper product in at the proper timing on controlling these late season insects because if we let those go it's really just going to kind of eat up whatever little profit that we might be able to try to salvage out of this late planted soybean. Especially down in SE Arkansas in the flooded conditions it's really a field by field basis. I'm telling most of the farmers I'm talking to, try to keep as much as you can. Several of the fields I walked were starting to go into reproduction and so those beans were moving along pretty well before the flood, but a lot of these fields either the entire field was destroyed or the bottom half of the fields and so a lot of these farmers are having to kind of look at these fields as two different crops. At this point we just need to do everything we can to try to salvage what we can. Hopefully some of these points I've given you you'll can take and try to help manage what you got now or try to start over and try to do the best we can. Hopefully we'll have a mild summer the rest of this summer and this fall we won't have an early frost and especially these late beans down south. Maybe we can get them out before we see a killing frost. 

Tom: It really is kind of a worst case scenario because you think about we had all these inputs in the crop, right. We had all our herbicides, pretty much laid by, everything was laid by when this hit so that makes it hurt that much more and that much more frustrating for these guys. And you're right, it's going to be a management nightmare and so, but what else are you going to do. You've got to get back in there and replant and just do the best we can. Like you say we hope that we can get the temperatures in October to mature everything on out. Well anything else we need to talk about? 

Jeremy: No I think we've covered, this topic we've covered just about everything. 

Tom: I just want to remind everybody out there spraying weeds right now, pigweed is coming on strong. I looked at a couple more fields today that Flexstar just didn't do the jobs. So our PPO resistance in those pigweed populations, like I said earlier appears to be spreading a little more, so make sure you have a plan B other than Flexstar out there available in these fields. And we get into cotton this time of year we're talking about post directed laid by applications. Not many folks want to do that anymore, but if we're looking at cotton right now, Diuron is a cheap post direct herbicide, put it with MSMA, you can put it with Roundup, you can put it with Liberty, you can put it with Enlist if you're an Enlist system, or you can Xtend in the XtendFlex system up until June 30th. So we need to think about using these residuals to finish out our cotton crop because our cotton's just now really getting going. It seems like it's took it forever to get to this point. We need to go ahead and get it laid by and get the pipe out to finish out the season, most of it. Well with that, Jeremy you got anything else?

Jeremy: Nope, appreciate you letting me use this format to get the information out.

Tom: Well yeah, we appreciate you joining us especially at the last minute. I called you a couple of hours ago to see if you'd do this.

Jeremy: This is one of those things we're trying to get as much information out as quick as we can. There's a lot of people asking questions, so we're using just about every format to try to get information out.

Tom: All our numbers are posted somewhere on our website. You can text us, call us, you can e-mail us. We'll be happy to come look if we need to look at a farm or if we need to just answer questions. That's what we're here for. Right?

Jeremy: Absolutely

Tom: So I want to thank everybody for listening today and again I want to thank Dr. Jeremy Ross, our extension soybean specialist for joining us. Join us next week. Dr. Jason Norsworthy will be discussing late season weed control issues that we're having and we're just playing these ear by ear, week to week, kind of seeing what the issues are. I want to thank everybody for joining us for this episode for the Weeds AR Wild podcast series on Arkansas Row Crops Radio.


End notes: 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.