Weeds AR Wild Series, Season 2 Episode 16. 
Title: Coating Loyant and Novixid on Fertilizer
Date:  June 8, 2022

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

Dr. Jason Norsworthy: Welcome to the Weeds AR Wild podcast series as a part of the Arkansas Row Crops Radio. My name is Jason Norsworthy, Distinguished Professor of Weed Science with the University of Arkansas System Division of Agriculture. And today, I'm excited to be joined by one of my grad students, Bodie Cotter. Bodie, hey, it's good to have you with us today.

Mr. Bodie Cotter: Hey, it's a pleasure to be here. Thank you for having me.

Jason: Bodie. First of all, I have to get this out. Bodie is finishing his master's project. He's probably a few weeks, months from finishing up. And then after that, Bodie, my understanding is you're going to go to law school.

Bodie: That's correct.

Jason: So yeah, sure. You have some exciting, plans in front of you with law school being in the future. But with that, we're here today and we're going to talk about coating herbicides onto fertilizers, things like urea, potash. And there's some specific herbicides that you worked with in terms of your research. And that was, you did a lot of work on Loyant and you did some work on Novixid where we actually coat those materials onto things like urea. When we take a look at products like Novixid and Loyant and we coat those onto urea, what are some advantages of actually coating those materials onto a fertilizer? And what did you see from a weed control standpoint with those products?

Bodie: You know, we come down to the root of one of the problems we had, which was off-target movement and being able to coat these herbicides onto urea, we're able to potentially reduce that off-target movement. So, then that leads to the weed control question at point. With Loyant, we're able to successfully control hemp sesbania, rice flatsedge, and ducksalad – when coated on urea. And with Novixid, we’re able to successfully control barnyardgrass, yellow nutsedge, hemp sesbania, rice flatsedge, and ducksalad. Now if it seems like we added a few weed species in there, we did. With Novixid we've got the addition of grass with the active ingredient penoxsulum in it. And that additional ALS herbicide allows us to better control barnyardgrass and offer better control for yellow nutsedge as well.

Jason: Yeah, it's interesting that you mentioned that. And you're right. I mean, I saw the plots. We walked the plots, and we did have some grass control there. But you know, when I look at the Novixid label, Corteva does not actually have any grass species on the Novixid label, but I agree with you. If they're small. One thing that I saw in your work that we've done over the last several years, is that overall I think the herbicides are probably more effective with a spray than when coating them on urea. So again, I mean, I've killed barnyardgrass with Loyant, if I spray it. And you saw the same thing in terms of your sprays, but when we coat it on urea or on potash – overall, you just don't have nearly the activity that you would do with a spray. Would you agree with that?

Bodie: I would agree with that. You know, we did some smaller studies looking at different flood depths associated with applications, or following applications, of Loyant coated on urea. And regardless of flood depth, we were unable to successfully control barnyardgrass with Loyant alone.

Jason: Now, again, that doesn't necessarily mean that this isn't a good option. I really like the fact, if you're in an area where you're concerned about off-target movement, coating it on fertilizer is an option. But overall, what we've seen is you're really going to only pick up those species that appear to be highly sensitive to these herbicides. Those that are somewhat marginally controlled or you need a full rate in order to control those, you're probably not going to control those if you coat it onto urea or some other fertilizer. Some other things that you mentioned there at the start was, one reason we do this is because of the off-target movement issue, drift issue. And I know that you actually did some work in soybean looking at drift rates of a spray on the soybean versus actually coating the material onto urea and looking at equivalent drift rates on the soybean. What did those results show?


Bodie: So we actually looked at off target movement involving drift rates, or what we like to say low dose exposure rates, of florpyrauxifen-benzyl Loyant. And we looked in two different scenarios where we had what we can consider a conventional wide row soybean planted on 36-inch beds here at Fayetteville. And then we also did it where we used a drill and drill seeded the soybeans, which you see from time to time in eastern Arkansas when you see soybean fields. Really was no difference in injury between those two trials, when we're talking about injury from coated applications of Loyant or from spray applications of Loyant. But when we had the spray applications at a 3 fluid ounce rate, which would be a very high drift rate, we actually saw a complete soybean death from that rate when it was sprayed onto the crop. But whenever it was coated onto the crop, we rarely ever exceeded 20% injury.


Jason: Yeah. So basically, also you don't expect a prill to move as far as you would potentially a spray droplet. Now, that does not necessarily say that you can't drift. I mean, can you drift a fertilizer? Absolutely. You can drift a fertilizer. You know, I saw that Dr. Roberts actually sent out a tweet here a couple of weeks ago. Just mentioning the fact that fertilizer drifts in high winds, and you sure don't need to be spraying in high, windy conditions. But with that, even though we're not eliminating it, we can definitely reduce the risk of off target movement on to soybean, if we coat this stuff on fertilizer. Another thing to mention is, it's really all about the quality of the fertilizer. You can have something that's going to produce a dust. If it produces a dust, dust has a tendency to move long distances. If it moves long distances, it's probably also going to do a better job of coating a leaf surface such as soybean. So you've got to have a prill, and that prill has got to be able to fall through the canopy and not necessarily see coverage of a crop such as soybean, if you're going to minimize the risk of physical drift based on the work that you've done. But in addition to that, you know, there's always discussion. “Well, is the off target movement purely a function of physical drift, or is there also a volatilization component it associated with that?” And, you actually took some Loyant. We coated it on urea. We applied it to wet soils. Dry soils. I mean, trying to basically cause the material to volatilize. What did you see in those trials?


Bodie: You know, we use those coated urea prills with Loyant and we applied them to flats in low tunnel volatility trials. And we were trying to recreate what we think would be optimized volatility conditions within those low tunnels. And what we saw was regardless of soil moisture. So like you said, we had a saturated soil, we had flooded conditions and we also applied it to dry soil. We saw no differences in volatilization from those. And we also collected some volatility data using high volume air samplers to confirm what we saw visually in the field. And there was very little to no injury. So that confirmed that coating it to urea would not increase any chances of volatility events occurring even under those different moisture conditions.


Jason: Exactly. So again, volatilization is really not a component. It's not a concern when we're spraying these compounds, Novixid, Loyant. Whether we're coating them onto fertilizers. We saw no issues associated with that in regards to volatilization. Loyant and Novixid had a use rates: Novixid 27.4 pounds, I'm sorry, fluid ounces of material that you need there, whereas Loyant – you only need 16. And if you take a look at the 2EE recommendations, Corteva recommends no more than 27.4 fluid ounces of Novixid per 150 pounds of fertilizer. And then also with 16 ounces of Loyant per 100 pounds of fertilizer. But what has been your experiences when you're mixing, you're mixing these products, you're mixing a fluid with that of a fertilizer such as urea? Can you get too much of a liquid onto fertilizer? And if so, what happens?


Bodie: You know, I do think you can get too much of a liquid on a fertilizer. I mean, for those of you that have been around fertilizers and seen how they react in higher moisture environments, if you get too much, you it will cause them to stick together. It'll be a less broken apart substance, which will lead to other concerns and problems in itself when it comes to application time. So you really want to make sure you're getting the right recommended rate of whichever material onto the urea to ensure that you don't have any other issues after the fact.


Jason: Yeah, you know, one way of actually getting around that is moving to something like muriate of potash. Something that's not going to be is as soluble or dissolve. Because what happens is, when you apply these liquid herbicides to fertilizer such as urea, you tend to dissolve that urea prill. And just based on what I've seen, I don't like to go much more than 15 to 16 fluid ounces per hundred pounds of urea. So with that, I mean, you start getting higher than that I've ran into issues. I heard of an instance here, I guess it was last year where an individual actually had too little fertilizer per the amount of liquid that they were applying and had some issues in terms of getting a material out of a plane. So we don't want to run into that. And I think if we stick to 15, 16 ounces per about 100 pounds and don't go less than that from a fertilizer standpoint, we should be fine there. You know, if you take a look at these labels, most of your work, you look at actually putting this stuff out pre-flood and you saw a little bit of flexibility that you had in pre-flood. But the two doubly recommendations from Corteva, those are actually for post-flood applications. Talk a little bit about weed size and the importance of small weeds.
And what are your thoughts there in terms of controlling those weeds?


Bodie: Yeah, when we look back at some of the some of the research we've done over the past two years, one of the common denominators we saw was about effectively controlling it with these coated application methods, was weed size. And weed size plays a lot into to being able to control weeds even that you would normally be able to control with Loyant. But when you increase your weed size, like say if you've got a 4 to 5 inch flood in a field and you drop in coated-on urea Loyant, you're going to expect less control. If you've got, say, a hemp sesbania plant, that's 50 to 70% out of water because you're just getting less of that herbicide interception with the plant material.
Jason: Really the uptake of the herbicide is going to be in the water itself. When we take these materials and we coat them on to a prill, you're not getting any interceptions. So the material is going to have to be active in the water taken up there. And if you go and you look back at the labels or these recommendations from Corteva, they're going to recommend 70% of the weed be submerged. I really think based on what I've seen in the field, that's a good estimate. If you have 50-60% of that weed, it's going to be out of the water. You have a tendency to increase your risk of missing those weeds, you know, things like coffee bean or hemp sesbania – five, six inches. If I've got a three-inch flood, four-inch flood, something like that, five, six inches, I'm good in terms of controlling it. That's probably the break point. When I start getting above that, we start having some issues. And you know, Bodi, you looked at actual weed sizes where we looked at small weeds and we looked at large weeds. And you definitely saw a break depending on the timing.


Bodie: Sure. Especially, you know even an easier to control weed like hemp sesbania with Loyant, when we got up to approximately ten-inch weed size or even a little bit greater. Our control started dropping off pretty drastically.


Jason: Yes. Also, when you think about a herbicide that you're putting out just right in front of the flood or maybe even dropping this herbicide into the flood shortly after flood establishment, at times we have excessive rainfall, levees break, we lose water. Various reasons we may lose water from the field, and some of your data said that we needed to really hold that hold that water as long as possible before that water starts moving. Before we start moving it potentially from bay to bay or again. But hopefully we don't break levees. But if levees begin to break and we begin to lose water, we could have some issues with herbicides like this that are active in the water. And so with that, if you take a look at the recommendations we recommend as well as, again, what I think Corteva is recommending – at least ten days, we'd like to see that herbicide held in the water without it moving in order to get optimum activity of the herbicide. Otherwise, we have a tendency to have a little bit less control than what we would expect based on our research. And so with that Bodie, is there anything else that you've learned from your studies over the last couple of years that you would like to add as it relates to Novixid, Loyant or coating herbicides onto of various fertilizers? 


Bodie: More, just so from a practicality standpoint. Whenever you're putting out these herbicides coated on urea, it's very important to be able to get that water onto that herbicide coated prill as soon as possible. Because the amount of time, as you increase time from your application to your flooding, you've got the potential of herbicide break down or other environmental influences to lessen your weed control.


Jason: And I think that's probably why Corteva actually recommends not putting it on dry ground, putting it actually into the flood. I know most of your work, you actually looked at putting it on fields where at times, they were dry. At times we had rainfall events and we had wet soil in. And there's all different conditions under which you applied these materials. But overall, I believe Corteva is recommending that it go onto a flooded field and I understand the importance of that, because if that field is flooded, you're not having to wait to get water across it. Some of these fields in Arkansas, I mean, I've talked to some growers that’s actually said that it may take them as many as 12, 13 days from the time that they get urea out to until they can actually get a flood across an entire field. And you can't wait. A product like this – I'll tell you, you can't sit there and wait 13 days because this herbicide is not going to have any activity until you get water on it. You're not going to get the post emergency activity like what you get with, for instance, a Loyant spray, a Novixid spray. You've got to have the water there if you're going to have activity of these herbicides. So with that, anything else, Bodie, about that you want to add?


Bodie: I think we've covered it about all.


Jason: Okay. Well, hey Bodie, I really appreciate you joining us today. And again, good luck as you begin to start law school. And I want to thank all of our listeners for joining us for this episode of the Weeds AR Wild podcast series on the Arkansas Road 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.