Title: Rice and Advice, Episode 2: Rice Preplant and Early Season Fertility with Jarrod Hardke & Trent Roberts (4/16/21)

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

Jarrod Hardke: Welcome to Arkansas Row Crops Radio. IÕm Jarrod Hardke, Rice Extension Agronomist with the University of Arkansas System Division of Agriculture.

Today on Rice and Advice, Episode #2, I have with me Dr. Trent Roberts, Extension Soil Fertility Specialist and weÕre going to talk a little about rice pre-plant and early season fertility. HowÕs it going Trent?

Trent Roberts: ItÕs going good Jarrod. I got my jacket on from keeping my rice seed in the bag for now. 

Jarrod: There you go. The season is starting to take shape a little bit. We do have some rice planted in the state, moving along, but still plenty of the season to go, so we felt like now is certainly still a very good time to jump into this topic, again pre-plant and early season fertility. So one of the things we certainly get a lot of questions on IÕd kind of like to discuss with Trent and get him to share his thoughts on is phosphorus and potassium, or P and K timing of application. So just kind of picking those one at a time, Trent, talking about phosphorus. WhatÕs the idea application timing here that weÕre talking about or what things should folks consider in their phosphorus application time?

Trent: I think when we focus on phosphorus specifically, the two things that come to mind are, what is your soil testing level. Are you in a medium category, low, very low, but in a perfect world, we want our phosphorus to be pre-plant incorporated as close to planting as possible. ThatÕs our perfect scenario. Timing and rate are really the two important things that we have to think about. Phosphorus is relatively immobile in the soil, so thatÕs why that incorporation component is important. We want to get it mixed into the root zone where that young rice plant, the small root systems can access it because typically when weÕre going to have the hardest time accessing and utilizing phosphorus is in the situations weÕre discussing now where weÕve got small rice, weÕve got colder, wetter soils. So anything weÕve done to help put that phosphorus in the root system is going to be a big benefit. But timing of applications is important because the longer phosphorus remains in the soil the less soluble it becomes. So what we want to try to do is apply it as close to planting to where itÕs relatively soluble in those early growth stages so that the plant can actually take advantage of it. But really when you start looking at low and very low soil test values, you need the phosphorus period, right? So whenever you can get it out is important, but trying to identify fields where you have medium soil tests, those are better candidates for application timing in the fall or earlier before planting. When weÕre in those low and very low soil test categories, thatÕs where we anticipate seeing the greatest yield increase and the greatest probability of a yield increase.

Jarrod: You mentioned the pre-plant incorporated and certainly getting it incorporated is going to make it safer being incorporated in the soil, but with a lot of the shortened time tables that weÕre on, especially the past few years and so far this year thatÕs true too, are we risking much of anything by working in a fertilizer rig in there when weÕre trying to get the tillage and everything slicked off is not that feasible, are we risking or losing anything by making these service applications after the rice fieldÕs been prepared.

Trent: I think we can put phosphorus out post emergence and especially if weÕre in those lower or very low soil test categories. WeÕre going to need it to maximize yield and productivity. Part of the issue you get into there is, we mentioned phosphorus being immobile, so unfortunately those roots almost have to grow up to the fertilizer and unfortunately that doesnÕt happen usually until after we apply the flood. And so thatÕs where that incorporation becomes important is the lack of mobility of the phosphorus fertilizer really means that if we donÕt mix it in, the roots have to grow up to where the fertilizer is at the surface. Like I mentioned, typically in our production systems those roots arenÕt going to get up there until post flood. So that delay in accessibility of the phosphorus fertilizer is what can lead to yield reductions and potential deficiencies that we might see. 

Jarrod: So the very low and low soil test categories for P we are going to be better off trying to get it out there incorporated if at all possible, but again as close to planting as possible so again weÕre kind of working with a double edge sword with the current conditions weÕre working in, but I also heard you mention certainly, even after planting, getting phosphorus out there, so when I think of like clay soil situations, donÕt necessarily, we hadnÕt gotten in to pot ash in potassium yet, but when I think them generally not needing that, but they might need phosphorus, thereÕs some potential there for maybe having some other things going out, being able to wait until that timing and other opportunities. We may get into that here just a little bit later, but certainly that dimonium phosphate and triple super phosphate were similarly priced, wouldnÕt you want to go after the rice is planted and take a little bit of the pre nitrogen in that to go out there in that scenario? Assuming I think theyÕve separated a lot in price this year, but previously they were pretty close.

Trent: Anytime you can get nitrogen for free thatÕs a good decision to make, so if that and triple super phosphate is relatively the same price, the way that I equate that is that nitrogen youÕre getting for free. When the price starts to separate then itÕs a little of a different scenario. I would say pre-plant incorporated, triple super phosphate is going to be my go-to. Typically because itÕs cheaper and weÕre probably not going to be able to utilize any nitrogen in rice thatÕs applied preplant. But you brought up clay soil which is a very specific situation and if weÕre applying phosphorus post-emergence, then I think there is some benefit to going with a DAP or MAP or a phosphorus product that has nitrogen included. And the reason I say that is whether youÕre on a clay soil or silt loam, the nitrogen is typically going to help stimulate that root growth which increases soil expiration and then the accessibility of that phosphorus fertilizer, so post-emergence IÕm definitely going to have a preference for a nitrogen containing phosphorus product like MAP or DAP.

Jarrod: Ok, good deal. Like I said we kind of focused on the phosphorus part of things first, but now kind of shifting gears over to potassium or pot ash. What are some go-to tips there for timing of application going back to that angle as well?

Trent: So when weÕre talking about potassium, I donÕt want to over simplify this, that the window of opportunity is very wide. ItÕs much different than phosphorus in terms of how it interacts in the soil, relative mobility, solubility, all those types of things. So obviously we want pre-planting corporated, as close to planting as possible as idea. We can get really good responses, hot ash fertilizer, all the way out into reproductive growth. So the timing isnÕt nearly as critical for potash or ? fertilizer as it is for phosphorus. To me it really comes down to whatÕs the best for your particular production system. If we are in those low or very low soil test categories, then weÕre probably going to need that case sooner than if we were in a medium or higher soil test category. 

Jarrod: So thereÕs been some questions in recent years talking about what youÕre already touching on a little bit, but like you said that window is really wide for us to be able to get a response to pot ash in rice which one of the great things about it we can easily run into deficiency situations. We have a great opportunity to still recover most if not all of our yield in those scenarios so weÕve been asked some in recent years, should we be shooting more for what has been our traditional approach of putting pot ash out upfront or early, whatever window or just past emergence or pre-plant incorporated in there or should we be splitting it up some, or to have some go out very early and some later? We get that question from time to time. 

Trent: One thing is we donÕt have a lot of research in the value of splitting potash applications in rice and I think some of that is probably coming from the work weÕve done in soybeans where there probably are obvious benefits. I do think that in some scenarios where weÕre recommending pretty high rates of potash that we could see some benefits especially on our lighter textured soils, of splitting those applications. WeÕre going to be in a very low soil test categories before I think weÕre really at an application rate where we might benefit from some split applications. But in those low soil test categories is also where you want to make sure you have at least a portion out pre plant. ItÕs definitely something we want to look at going down the road, but the thing that I fall back on is rice isnÕt nearly as responsive to pot ash as soybean and so thatÕs where we might see the benefit of split applications in soybean where we might not necessarily see the same magnitude of response in a rice crop. 

Jarrod: LetÕs bounce over to another slightly different topic and talk a little bit about zinc. Always a big early season question and certainly the first thing we usually talk about with zinc at planting time is using it as a seed treatment and the factors should be considered in what rate, primarily what seed treatment rate we need to be using in these scenarios.

Trent: These seed treatment are always a little bit tricky to discuss just because thatÕs an ever evolving kind of market place. Seems like thereÕs a lot of new products all the time. They change things a little bit here and there, but I think the fundamentals of zinc seed treatment are, theyÕre really only suited for very specific scenarios. You really can only use zinc seed treatments when thereÕs a potential for marginal zinc deficiency. And I think we start with our soil test, right? What is my soil test recommending in terms of zinc requirements and that will tell you a lot about how the likelihood of a zinc seed treatment being beneficial. If youÕre in a soil pH and youÕre in a soil test zinc level that recommends five or ten pounds of actual zinc per acre, the a zinc seed treatment isnÕt going to get you very far. However, if youÕre kind of boarder line in terms of pH or boarder line in terms of soil test zinc, thatÕs where you can see a benefit from the zinc seed treatment. What do you think about zinc seed treatment rates?

Jarrod: I mean from a rate I think we continue to see a quarter to a half pound per hundred weight has consistently looked very good from a seed treatment rate standpoint. I think itÕs necessary to mention that there are a few products out there that may be getting applied as zinc seed treatments that may go on the seed very well but the actually amount of zinc going on there is extremely low compared to those recommended rates, so I think we need to be mindful about some of those that are out there that the price point may sound good and may sound like it goes on the seed extremely well but look at that rate and check the math on that youÕre actually getting a quarter to a half a pound per hundred rate of actually zinc on that seed. I think thatÕs been something thatÕs started to pick up that last couple of years, some of these formulations again but the idea to improve, are coverage and how well we get it on the seed and how uniformly but I think to get there has dropped that actually amount of zinc. Something that we should be watching out for. Like you said the lower the soil test zinc level gets the more itÕs going to be an issue of having less and less on there. Better coverage is great but giving up quite a bit of zinc right there in the immediate root zones for young rice is going to be an increasing concern for me. 

Trent: I think the catch twenty two would be zinc seed treatments is, the powder formulation is typically zinc oxide and we use those because they have high analysis but they have ? coverage, more sticking affect.

Jarrod: TheyÕre pretty chalky from that standpoint trying to get thinned out enough for good flowing coverage, absolutely. 

Trent: I hate to be that guy, but I am a soil fertility soil test guy and IÕm a proponent of building soil test values and time and time again zinc is the one nutrient that I feel very confident that we could build soil test values over time. And to me thatÕs the best way our money can be spent. 

Jarrod: Oh I agree too. Getting a zinc seed treatment on there is pretty cheap, good, efficient insurance to help minimize especially early season issues but thereÕs still not going to be replacement for us trying to build those soil test levels. And weÕve certainly talked about the value, you and I have discussed before the value of trying to go with zinc sulfate as a fertilizer when we have low soil test levels to try to build those soils as opposed to the reactionary approach of a post flood, now I have a zinc deficiency issue spending money flying zinc onto the field when that one gallon, say roughly one gallon of product, one pound of zinc to correct the problem costs as much as that roughly twenty five, thirty pounds of zinc sulfate out there to build soil tests, so try and keep that in mind just to your point in going after building the soil test from availability and then the seed treatment is good insurance. Also keeping in mind there is also too much of a good thing. You canÕt just put all the zinc in the world on the seed and expect no negative response. You do start I think itÕs up around one pound instead of a quarter to a half, once you get to one per hundred weight thatÕs where you get into some actual seedling toxicity from there being too much in the zone there so anyway I already kind of touched on part of it but weÕre going to talk a little bit more about fertility programs involving zinc and I know I mentioned the zinc sulfate but there are some other zinc containing products like MESZ, stuff like that. What are your thoughts differentiating those when weÕre talking about in a zinc scenario. 

Trent: First off I think MESZ which stands for micro-essentials zinc is a great fertilizer product. ItÕs what we call a multi-nutrient fertilizer product because all of the nutrients in that analysis are found within each prill and so I think the analysis is twelve percent nitrogen, forty percent P2O5. It has ten percent sulfur and one percent zinc. And first and foremost I consider MESZ a phosphorus fertilizer source and so thatÕs really what we need to focus on utilizing it as. But to me itÕs perfect for some of these marginal situations that weÕve discussed where the soil test level or the pH is borderline or itÕs also great for what I might consider like a maintenance program in the sense of the zinc that weÕre going to apply in a hundred pounds of MESZ, so one pound of zinc per acre. ThatÕs a good maintenance program for a rice/zinc management. So there are a lot of good applications in terms of MESZ for not only various nutrients but zinc as well but I think you start with your phosphorus fertilizer rate and you can apply MESZ to get that P2O5 requirement and then in those low soil test zinc situations you may have to blend some zinc sulfate in there just to help get you to a level that youÕre not going to experience any yield loss.

Jarrod: ThatÕs a great point trying to find that happy medium and always keep in mind it can simpler to run one product for this, one product for that but we can always go that route as some of these blends to accomplish all our goals and at the same time hit our price point in keeping the economics lower so definitely some advantages to be had putting those together. So weÕve talked a little bit about phosphorus, potassium and zinc and really kind of more in-season applications primarily our pre-plant fertilizer topic. But it seems like each year we also get into discussions about use of starter type fertilizers in rice and when I say starter type I guess I should say just fertilizer used with a starter concept in mind with early post emergence. So I want to kind of again discuss about that with you about situations where starter fertilizers in rice might or might not be useful. 

Trent: Well so the one thing that I would clarify to start with is I would never really recommend putting out nitrogen pre-plant, unless it was that triple super phosphate vs that scenario we discussed earlier when getting the nitrogen for free. I think if weÕre talking about starters in this scenario itÕs exactly what you said, an early post-emergence, so two leaf type rice scenario. I definitely think thereÕs situations where we could benefit from that, I think first and foremost, heavy true clay soil where the rice comes up and itÕs short and just sits there, I think thereÕs areas where youÕve got early season environmental conditions that are not favorable so cold and wet. As Rick Cartwright always said, if rice isnÕt growing itÕs dying. And itÕs one of those types of situations where a little bit of starter fertilizer that contains nitrogen, especially nitrogen and phosphorus, can be very beneficial to get that rice kind of moving in the right direction. So definitely some scenarios where it can be beneficial in the long run it may not add up to yield differences but weÕve had some recent research that has shown differences in canopy coverage, potentially differences in days to flood. So those are healthy rice scenarios, but when youÕre talking about a sick rice scenario, fifty pounds of dap or a hundred pounds of ammonium sulfate, it can make the rice look a whole lot better and it can make you sleep a whole lot better, and those are two things that are great. 

Jarrod: I agree and certainly love the comment, the rice is either living or dying, there is no third direction. ThatÕs really what weÕre working with, but yeah using those starters itÕs definitely situational and weÕve certainly gone through a lot of data and not just ours in Arkansas, but other states in and around recently. ThereÕs certainly a lot of inconsistency to the response of rice to a starter fertilizer and certainly just to clarify what weÕre talking about, a nitrogen based fertilizer, again could be dap, could be urea, could be ammonium sulfate roughly in that two the three leaf rice growth stage. I donÕt think we kind of touched on that timing weÕre specifically talking about, but itÕs occasionally shown a little bit of a yield bump at those times but most of the time as you already said it can be more of a growth response, kind of canopy coverage and seems to occur more often on our clay soils where we get a noticeable response as opposed to our loamy type soils. Having said that we were playing around with some timings last year and saw a little bit of a response on some loamy type soils but it was also a little bit later stage, so you start getting into that discussion and if weÕre already going that late why would we not just go ahead and fertilize and flood? When youÕre already knocking on the door of that window, so again get into a lot of layers I think at the starter fertilizer timings, but ultimately if someone is interested in doing it they definitely do not need to apply anything before itÕs a full two leaf, count two leaf collar, should be a third leaf coming out. That would be the earliest to do that. And hopefully get a rainfall or a flush to incorporate. WeÕre hoping rain as opposed to flush. But get that incorporated then hopefully there will be some benefits but we have seen benefits not long after the pre-flood application, which we werenÕt pushing things along, we could have taken them further. The canopies caught up to one another, where there was no starter and there was starter pretty soon after everything did go to flood, but again where there was some starter on some of those clay soil sites, probably could have been pushed to flood a little bit quicker as you said moving some maturity ahead in time, so there can be reasons to justify it agronomically, but if your sole reason for doing it is a yield gain, thatÕs not what weÕre ultimately going to necessarily get out of it. May get a couple of bushels out of it to pay for it, and certainly the time savings and efficiency may help us as well from an economic standpoint but definitely donÕt need to be slinging starter fertilizer left and right everywhere this spring. This would be my take on it. 

Trent: Yeah and if IÕm a rice producer, itÕs going to be environmental situation and I think you truly have to take kind of every situation independently to be successful with that. Along the lines of what you said, IÕm going to look at my clay soils first, IÕm going to look at my cold, wet soil second, thatÕs kind of the staging IÕm going to go through when you think about it. You brought up to me a very important thing, the timing, two leaf or later is important, because really that rice plant lives off the seed until that two or three leaf growth stage. ThereÕs no sense in us really putting out nitrogen before then because the plants living off the seed, so being able to get it out when those roots are actively taking up the nitrogen is important.

Jarrod: Yeah thatÕs the key there. LetÕs get it out once theyÕre finally taking it up and while you were talking there I was also reminded certainly like you said the clay soils and some of those stressful situations also often think of the White River corridor of production, pretty high pH in soils, we continue to try but lower fertility levels and you get into cool wet conditions and that rice can struggle mightily and though weÕre talking about loamier type soils, those certainly could be candidates for the rice is just not getting very tall or growing off very well that they could be a candidate again. Not necessarily see a dramatic yield response but in terms of getting them moved along in time when theyÕre struggling in that scenario. There may be a benefit at times situationally to do something with those just to get them moved along. A lot of times a little dry weather, sunshine and heat, thatÕs just as good as any starter fertilizer going out there, but again weÕre talking about situations where thatÕs not happening.

Trent: Definitely, definitely true. I think, to me I always keep going back to clay soil. Seems like everything can be going perfect and that rice on the clay soil just stops growing. And it just sits there and youÕre like well, itÕs too short for flood, you know, the weeds are coming and what do I need to get that extra little boost where I can get it flooded. To me thatÕs the kind of scenario that weÕre talking about. 

Jarrod: Absolutely. Yeah. There needs to be a struggle situation most of the time to see a measurable benefit. I think you touched on one of your first comments. Healthy, good growing conditions rice is how a lot of the work has been done and thatÕs just been the nature of it and so not seeing a lot of responses there through most of the literature work, but we start getting off into some of these other situations where the rice is struggling along a lot more and certainly more potential to maybe put it in use, but again just so everybody listening to this is getting the point, it doesnÕt mean look for every excuse you can find to go slinging starter fertilizer this spring to get a little boost here. ThatÕs still going to be twenty plus dollars out of your pocket to make that application, so letÕs make sure we need it and just a minor slowdown in growth is generally not going to be the end of the world. So just try to keep that part of it in mind. Well Trent  . . .

Trent: Penciling out that ROI make a difference. Just remember that those starters are probably going to have the lowest return on investments, so just be discreet about when  . . .

Jarrod: Yeah and of course I think thereÕs a very nice opportunity if weÕve got fields, IÕm just thinking my way through this, if we do have fields that have a history of struggling early and when we talked about certainly the phosphorus not wanting to get out there too late especially in the very low to low so, we would certainly want to avoid those situations with the comment IÕm about to make, but I think there could be some argument for putting out like we were talking about even initially some dap or some of our fertilizers again after that rice is up even at that two leaf stage to kind of get everything going at once. Save it for then again assuming all the prices are relatively equal and we may know that this field had the tendency to struggle on a regular basis. Maybe thatÕs one way to solve part of that problem. 

Trent: Well we could solve the problem by just proposing and putting out a study because I guarantee ya if we tried to get cold wet conditions to actually test starter weÕd have the best planting conditions in the world.

Jarrod: So thatÕs a funny THING that is always true. You pick a hot button topic and we dive off into it full bore with test all over everywhere and we get the exact opposite conditions that year. ThatÕs good thing to remind everybody of too. ThatÕs the fun and the chase and the thrill of doing the research side of it and sometimes be why the answer to stakeholder questions is, I donÕt know. ItÕs not because we didnÕt try, itsÕs because we just donÕt know. DidnÕt work out that way. It does tend to happen. 

Trent: WeÕre not as lucky as the weed scientists. You can always find weeds, right?

Jarrod: ThatÕs right.

Trent: Being a soil fertility and agronomy we canÕt always find the cold wet soils or the P responsive soils. Weed guys can always find weeds.

Jarrod: Yeah we can sit around and wait on those situations and scenarios. They happen or they donÕt. Well, I think weÕve talked about most of I guess what we wanted to cover today. Got any last minute words of wisdom for everybody this year Trent?

Trent: Well the only words of wisdom I would have is be diligent about your fertility programs. Remember how hard it is to correct a nutrient deficiency, should kind of dictate when you manage it and how you manage it, so zinc is top of the list and the hardest to correct so just make sure we take care of it first, phosphorus second and potassium kind of third, just a window of opportunity. As always, weÕre here to help, so reach out to Jarrod or myself with any questions that you have.

Jarrod: Yeah, you bet and thanks again for joining us today on Episode two of Rice and Advice, for Trent Roberts, donÕt guess soil test and for me. Again thanks for joining us on Arkansas Row Crops Radio. Have a rice day!

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.edu.