Read Full Transcript
[00:00:08] Mike Howell:
The Dirt with me, Mike Howell, an economics podcast where I present the down and dirty agronomic science to help grow crops and bottom lines. Inspired by economics.com, farming’s go- to informational resource. I’m here to break down the latest crop nutrition research, news and issues, helping farmers make better business decisions through actionable insights. Let’s dig in. Well, hello again, everyone. Welcome back to The Dirt. We are doing a live recording today. We are on location here at Mississippi State. It’s great to be back on campus. I was actually here for the Georgia Baseball series a few weeks ago. That was not a really good weekend, but having a great time here today. Did not realize that we were gonna be the opening act for the Zach Bryan concert when we came in, but really big event going on here on campus this weekend. A lot of activity around Starkville.
[00:01:04] Mike Howell:
We’ve got a soil fertility class here that’s gonna take part in this podcast with us and we’ve got Dr. Vaughn Reed, the soil fertility instructor joining us today. Vaughn, welcome to the dirt.
[00:01:13] Vaughn Reed:
Morning. Thank you.
[00:01:14] Mike Howell:
Vaughn, today I thought we would talk a litle bit about P&K removal and replacement. We’ve talked a lot about removal rates. We talked about that a little bit when we went through our economics website. That’s one of the calculators, one of the tools that we have there. You can put in your crop and see how much P&K is coming off with a 200 bushel corn crop. First off, if you will, introduce yourself to our listeners that are listening at home. I know you’ve been on before, but we’ve got a lot of new listeners, so if you will, introduce yourself and tell them what you do here at Mississippi State.
[00:01:41] Vaughn Reed:
Hi, my name is Vaughn Reed. I am assistant professor of soil fertility here at Mississippi State. Been here. This is my … Coming up on my fifth year here at State doing, um, I’m about a 60 / 40 split, so I spend about 40% of my time teaching, 60% of the time researching, which actually ends up being 100% of my time is always taken up by something. Like, we’re busy all the time. Our research focuses on soil fertility, nutrient management, even doing some precision ag within all crops growing in Mississippi and also just focusing a lot on soils. We’re always doing something. We always got a lot going on.
[00:02:13] Mike Howell:
Savon, I don’t know how this happened, but you did not mention extension. You don’t have an extension appointment?
[00:02:18] Vaughn Reed:
No, I do not have an extension appointment.
[00:02:20] Mike Howell:
I’m working to fix that. I met with Angus yesterday.
[00:02:31] Vaughn Reed:
Thank you. Listen, if I know anything, it’s I always eat another job.
[00:02:34] Mike Howell:
There you go.
[00:02:38] Vaughn Reed:
Right. Well, good. I’m glad you’re negotiating for me with Angus.
[00:02:42] Mike Howell:
No, we know you help out everywhere you can. You have to wear more than one hats on the university these days, so that’s just the way it works. Von, let’s get into it and talk a little bit about P&K. And before we really get into what we wanna talk about, remind everybody why P&K is so important in crop production.
[00:02:57] Vaughn Reed:
Phosphorus and potassium are generally the second and third nutrients we think about if we’re going in levels of a nutrient management plan. Nitrogen is the one that gets all the love, a lot of the attention. And it’s mostly because we’re just applying so high rates of that and we have to for corn. Less than that, we have to apply for cotton and obviously we don’t have to apply much, if any, for soybeans. And so those are the main crops we have in Mississippi. Phosphorous and potassium though are immobile nutrients. We derive them 99% of it from the soil, so we need to get it from the soil. And the soil provides most of it. We have to apply a little bit more to feed that soil, but that has to go up into the plant and it comes down to its mobility on how much that plant is going to need.
[00:03:38] Vaughn Reed:
If you go way back, and I realize I’m teaching a class and so my mind thinks in teaching in this scenario compared to extension or research. But if you go back to mobility, the original, like, background of soil fertility, you go back to a mobility concept, nitrogen is going to be yield-driven. The higher yields are, you need more nutrients. Phosphorous and potassium is a sufficiency. Once you get up to a certain level, you have maintained what your yield is going to be and applying anything over that is going to feed your soil, but not necessarily going to feed your plant all the time. Now, that’s very simplified as to what it is. We need phosphorus and potassium to really reach our 100% maximum yields we can have and then just making sure that there’s going to be enough in the soil there for it to be.
[00:04:17] Mike Howell:
Von we know that a lot of these crops are, you mentioned corn and soybeans, but we know they’re going to take off these phosphorus and potassium nutrients. Talk a little bit about what crops are high users of phosphorus and how much phosphorus can be taken off by one of these crops.
[00:04:31] Vaughn Reed:
For most of our, uh, row crops in the state, phosphorus is pulled out and I wish I would have pulled up these numbers beforehand. Phosphorus is pulled out in a moderate rate. A 200 bushel to the acre crop is going to pull out roughly 40 to 60 pounds of phosphorus. It pulls out a decent amount, but that number that we’re pulling out of the soil isn’t necessarily what’s going to be reflective on a soil test value. Corn, soybeans, cotton, all pull out a decent amount of phosphorus, not a huge amount, but a decent amount of it. If you go start looking at potassium, that starts to delineate a little bit. Cotton takes out a significant amount of potassium from the plant. For Mississippi bound, sweet potatoes takes out a lot of that as well. Corn removes second to cotton and then soybeans removes a decent amount of potassium as well.
[00:05:13] Vaughn Reed:
So all of these not nearly as much with nitrogen. They’re not removing as much as they do with nitrogen, but they still are removing a significant amount of phosphorus and potassium.
[00:05:21] Mike Howell:
And Vaughn, I’m gonna challenge you on that. I think there’s one crop that you missed and I think a lot of people overlook this one. What about forages? Hay production.
[00:05:28] Vaughn Reed:
That’s a very good point. Forages because we are removing so much biomass. So with row crops, corn, cotton, soybeans, we’re leaving a decent amount of biomass in the field. We’re taking out the nutrient rich part of it, the grain or the fiber, but for forages, we’re cutting that and removing everything from the field. Our forages are pulling off. They’re the highest remover specifically of phosphorus and potassium and of others. Nitrogen is pulling off a decent amount compared to corn and cotton, but phosphorus and potassium with forge is you’re pulling off a lot of nutrients.
[00:05:57] Mike Howell:
Vaughn, you kind of mentioned it earlier and we hear a lot about this, the soil bank and how much nutrients are in the soil bank. When fertilizer prices go up, growers kind of want to tap into that soil bank and maybe rely on that. Can we make a withdrawal from that soil bank? Talk a little bit about what we mean by the soil bank.
[00:06:13] Vaughn Reed:
When you said earlier we were gonna talk about banking and financing, this is where you were going with some of this.
[00:06:17] Mike Howell:
No, we’re, we’re going a little deeper here in a minute.
[00:06:20] Vaughn Reed:
Okay. With phosphorus and potassium, these are immobile nutrients and so we are basing those out of the soil. We are taking a soil test to tell us what’s there. There are multiple forms of each phosphorus and potassium within the soil. I generally split it up between two banks. There’s a solution and there’s a solid phase. Your solution is what is in water, in solution, within your soil at any one time, and it is what’s immediately available for the plant to take up. Then we have our solid phase, which actually has to melt or dissolve in order to refill that. Think about it as like an ice cube. If you’ve got an ice cube and then you’ve got water, you can take all that water away from that ice cube, but you have to wait for that ice cube to melt a litle bit more before you can remove more water from your glass.
[00:07:00] Vaughn Reed:
Our soil bank is that ice cube, is that solid format and it takes some time to refill that liquid that’s left behind. With a soil test, we’re trying to estimate how fast that solid cube is gonna dissolve, how fast that that solid phase is gona dissolve and make its way into solution so that plant can take it up. Soil test value is gonna tell you roughly what we think is going to be there, but it’s not necessarily reflective of the total amount of nutrients available in your soil. A total soil test doesn’t give you what is actually gonna be a plant available. It’s gonna tell us over 100 years what is there, but not necessarily what can be there for this year or the next coming years.
[00:07:37] Mike Howell:
Great point. And that’s something we need to pay attention to what is actually available. You kinda stole my thunder just a little bit. I told you we wanted to talk about banking and finance and that’s one thing that I hear in my travels that students coming out of college these days don’t have a real good understanding of banking and finance. They don’t understand how to manage money and I’ve heard that we need to do a better job teaching that to our students and I probably needed to do a better job teaching that to my kids when they were coming up. But relating that back to soil fertility, I’ve kind of been thinking about this for a while now. We mentioned the soil bank and the nutrients that are stored in the soil and this can be beneficial if we’ve got enough money or if we got enough nutrients stored up in the soil, but it’s only gonna last for so long.
[00:08:15] Mike Howell:
We can only tap into that for so long before we run into a negative balance. We’ve gotta replace it. But if I go down to the bank and want to get money out of the bank, there’s two ways I can get that money. I’ve got it in my checking account and I can go get that money. That’s my money. That’s free money to me. I can go get it and do what I want to. If I don’t have money in my checking account, I’ve got to go sit down with that banker and negotiate a loan and I’ve got to borrow money from that banker and I’ve got to pay that money back with interest. That’s somebody else’s money. When we start thinking about these nutrients, do these nutrients belong to the farmer or do these nutrients belong to the soil? And the more I think about this, you talked about the sufficiency level and how much nutrients are in the soil.
[00:08:52] Mike Howell:
Anything up to that certain point, I think those nutrients belong to the soil. That’s what’s naturally gonna be there. Anything above that is something that the farmers put there and that’s probably the farmer’s portion of it. That’s something he’s put there and he can probably pull off of those nutrients. Anything below that is the soils and it’s gonna cost him some interest to pull out of that. And that’s kind of where I wanted to get to today. If we start pulling out below that sufficiency level, if we pull out 40 units of phosphorus below that sufficiency level, how much do we have to put back? What’s the interest penalty on that? Can we put back 40 units and get back to where we were last season?
[00:09:24] Vaughn Reed:
That’s a really good point. The math of what the soil has available to it and what you have never makes sense. If we were removing 60 pounds of phosphorus from the soil, buy a corn crop, buy cotton crop, buy soybeans, by forages. I can’t just turn around and go put 60 pounds on it the next year and now we’re back level. It’s a balancing act, so you’ve got to feed the solution, which then in turn is gonna refreeze that ice cube. You’re putting money into your checking account to try and refill your savings account or pay back the loan that you’ve got and the math doesn’t work out perfectly. You have to put a significant level above that. Now, the numbers vary from location to location and that’s really soil chemistry based, that’s classification of your soil. It’s whatever that soil actually started out as.
[00:10:06] Vaughn Reed:
But you’ve got to put a significant amount above removal to actually start building that back up over time.
[00:10:12] Mike Howell:
Now you’re getting to my next point. You said it varies from location to location. That depends on what bank you go to. Different banks have different interest rates. If we’re talking about a sandy soil versus a clay soil, that interest penalty may be a little different, right?
[00:10:24] Vaughn Reed:
You’re right. If we are looking at a sandy soil, that might be your local bank. Does enough exactly for the location you are, but you’re not gonna go take out a 1.6 billion dollar loan from your small local bank. You’re gonna have to go a little bit higher above. That’s where we get into our heavier clay soils. If you go out east of here about 20 or 30 miles, you get into the black belt soils in Mississippi. Those are predominant heavy clay soils, CEC above 30, 40, 50 CEC. We are very heavy soils. That is gonna have a lot larger bank and it’s gonna take a lot more nutrients to slowly fill those soil test values over time. Sandy soils, we can refill that pretty quickly.
[00:11:01] Mike Howell:
Paul, we’re talking about replenishing the P&K. Is that interest penalty gonna be different for phosphorus versus potash?
[00:11:07] Vaughn Reed:
Potassium is fairly straightforward on … It’s gonna be CEC determined. So as you apply more, we’re gonna fill that CEC up and then slowly over time we’re gonna fill up that solid phase and those nutrients are gonna build up. Phosphorus is different in that it is not directly related to CEC, but things in the CEC are gonna dictate phosphorus. If you have more area within your soil that’s gona hold more nutrients, you have a higher CEC, you’re gonna have more nutrients like calcium, iron, and aluminum that are going to attract and hold onto that phosphorus. They’re not directly related, it’s indirect relationship between those. So the more of those you have available is determining how much phosphorous is actually going to be required to build those up. We’re gonna have some phosphorus go in over time and that’s gonna slowly start creating more and more insoluble nutrients and over time we’re slowly filling that bank up, but it’s not nearly as quick as what we would hope for it to be.
[00:11:58] Mike Howell:
Von, we had Brian Hopkins on several weeks ago and we talked about different strategies when it comes to nutrient management. We talked about the build and maintain. We talked about replacement. We’ve kinda beat around that topic a little bit today. I’ve got a couple of questions related to that. Is it possible to build the soil test level for P&K? And if it is, is it economical to do that?
[00:12:19] Vaughn Reed:
That’s a really good question. Like Brian Hopkins said, there are kind of two main approaches for phosphorus and potassium management. You can do sufficiency approach where you apply up to exactly what this year’s crop needs and then you stop and then you have gotta build and maintain that says, “I’m going to continue to apply above what this year’s crop is to build my soil test value up.” And then once it gets so high, we’re gonna tail off and maintain it. We’re gonna apply a lot less over time. The answer is yes, we can build our soil test values over time. That’s going to be very soil specific. Heavy clay soils are going to take a lot more nutrients and a lot more time to get there. Sandy soils aren’t going to take as long. Is it economical? It really depends on what the fertilizer price is.
[00:12:59] Vaughn Reed:
For this year, any producer who we’ve been talking to gives me a call and says, “I need to cut back on some stuff. What do we do? ” I’m saying we need to go back to a sufficiency solely apply what is the, available for this crop this year. Let’s not try and build our soil test values up and hope that in the next couple of years fertilizer prices go back down to a point where we can replenish those nutrients over time. Now, if we’ve had three or four seasons of drawing down those nutrients like we probably have in the past three or four years, it’s going to take a lot longer to build that back up. Then we have to try and find some way to not only rebuild, but also make sure that what we’re putting out there is still going to be enough for that crop.
[00:13:37] Mike Howell:
Von, let’s kind of wrap all this up into a nice, neat little bundle. Are we better off utilizing what’s in the soil when these prices get up really high or is it better to make an application at some level no matter what the fertilizer prices are?
[00:13:50] Vaughn Reed:
I think you try and utilize both. I think we need to utilize what’s in the soil, try and make that soil provide what that crop is going to need, but you’re still going to have to supplement something. If we can find a way of whatever you’re putting in, if we can cut that back but still maintain our yield by applying at the right time, the right area, the right source, the right placement, that would be heavily beneficial, but you’re still going to need to rely on what is going to be there for your soil to get up and really maximize your crop.
[00:14:15] Mike Howell:
Vaughn, we really appreciate you joining us today. I know we’ve covered a lot of ground here in a short time. Is there anything you think we’ve missed, any closing comments we need to talk about before we wrap up today?
[00:14:25] Vaughn Reed:
Right now, no, I don’t think so. I think we’ve hit most of the stuff that I was hoping we would talk about, but it’s just important to watch your soil test and make sure, even though, and I’ll be the first to tell you that a soil test isn’t going to be perfect, but just watch it and make sure that you’re not getting to a point that it’s going to cost a lot more money to really build that back up. We empty faster than we can put back into it. That time is a lot slower to build those values back up.
[00:14:49] Mike Howell:
Listeners, we really appreciate you tuning in. For those here in the live audience, we really appreciate you joining us this week. Great to be back on campus here at Mississippi State. Really appreciate y’all joining us. Those listening at home, if you will, hang on for just a few seconds and we’ll be right back with segment two. Farming isn’t farming without questions and now there’s a place to go for answers. At economics, an entire team of agronomists is waiting and ready to help for free. No question is too big or too small. Visit nutrient-economics with ake.com and submit your question with the ask an agronomist feature. Listeners, welcome back for segment two. We’re doing things just a little different for segment two this week. Since we’re live and on location here, we’ve asked the students to come up and ask some questions for us today. Instead of using your listener questions, we’re going to get the students to come in and do the aston agronomist section.
[00:15:43] Mike Howell:
Students, anybody that has a question, feel free to come on up and ask these questions.
[00:15:48] Speaker 3:
Would these same concepts on nutrient availability still be applicable on like international scales when the soils and the different crops would be different? I guess just dealing with the difference and how those two systems may interact a little differently with the same concepts of nutrient availability still apply, or is there still more research needed?
[00:16:05] Vaughn Reed:
That’s actually a really good question. Will the concepts that we currently use work on an international scale at different soil types? Depending on where you go and it also dependent on what kind of soil you have, what is the parent material of that soil and how weathered is it? And so if you go to an area in rainforest where those soils have been weathered with tons of rainfall over time and time is also in part of this as well, going to weather that soil even further, that soil chemistry actually changes a lot. Instead of us having a predominant CEC, cation exchange capacity, you can weather a soil to the point that you can actually start having some AEC or an ion exchange. Some of the nutrients we talk about as being immobile here at other more weathered soils or completely different parent materials that can actually flip and change that mobility.
[00:16:53] Vaughn Reed:
Most of what we talk about in class or extension specialists or extension agents across the US, it’s going to be very US based. Our soils are for the most part consistent on CEC and the soil chemistry standpoint, but it’ll change in other ways soil pH, mineralogy, some of the chemistry and physics oil change, but most of it is going to be fairly applicable across North America. As you go out and change soil types, it’s going to be completely different and would need to, I myself would need to start from ground zero to rebuild what I know about it because it’s just completely different. That’s a great question.
[00:17:27] Speaker 3:
Do you think that you have to replace everything that gets removed each year or do you think you can get away with not replacing nutrients at all?
[00:17:34] Vaughn Reed:
I’d have to have some more information, mainly telling where did we start? There is a workout there that says that there is luxury consumption of certain nutrients. Certain nutrients like potassium, like chlorine, those are going to move into the plant with water indeterminately. It’s just going to start moving into the plant. And so that plant is going to take it, go put it into storage, but not necessarily use it. We see this in cotton a little bit. We see this in, even though cotton uses a significant amount of potassium, we see this in soybeans, plants will take up more than what’s there, more than what is actually required to maximize the yield. So do we need to replace everything? Depends on the nutrient and depends on what your soil test has. If your soil test comes back and you tell me you have 500 parts per million Malik three potassium, which is a lot, then we would not need to replace what we’re pulling out of that.
[00:18:19] Vaughn Reed:
If we have low soil test values, then we would definitely need to consider replacing what we’ve pulled out of it.
[00:18:23] Speaker 4:
Thank you.
[00:18:24] Mike Howell:
Vaughn, I want to add on just a little bit to that. Great answer, but I’ve got a slide that I show in a lot of my talks that looks at the soil test averages from across the United States and if you look at the numbers on there, it shows the percentage of soils that are coming back testing below the critical value for P&K and it floors me when I look at that. I think the values for Mississippi for P&K are like 60 and 70% below the critical level and it’s worse than that in some other areas. Yeah, that’s exactly right what you said, but a lot of these soils that we’re looking at are below that critical level so we really need to pay attention to those soil tests and we’re not where we think we are on a lot of these soil tests. Make sure you know what’s in your soil.
[00:19:00] Vaughn Reed:
Right, right.
[00:19:02] Speaker 3:
Is it ever all right to skip a potassium or phosphorus application for a year or
[00:19:07] Vaughn Reed:
Two? Is it ever okay to skip applications? That really goes back to our soil test. Again, if we have a high, very high soil test, we could probably skip a season or two. If we’re starting to get deficient to the point that we need to be making applications, specifically with phosphorus, if we are in a low soil test and my recommendation says, “Let’s apply 60 pounds,” and I say, “Okay, well, I wanna go ahead and feed for next year. Let me put out 120 pounds.” That does not translate from one season to another. Doubling up this year doesn’t mean that my soil test is gonna be perfect next year. There’s some percentage of what you put on above, as we talked about earlier, is going to build up your soil test values, but it’s not going to be a one-to-one. It’s not necessarily going to be okay for crop to crop from one season to the next, but checking your soil test values, making sure it’s at least close to where it needs to be and then making those yearly applications if possible.
[00:19:58] Vaughn Reed:
For phosphorus, it’s better to split that application up one year after the other. You can’t double up or even triple up the year before and try and meet the next year and exactly get what you need. It’s a little more difficult.
[00:20:08] Speaker 4:
How do you determine what nutrients have been removed and what you need to replace?
[00:20:13] Vaughn Reed:
If you look up any nutrient removal calculators, there’s a bunch of the apps. Economics has got a nutrient removal app. Depending on where you are, your extension office or your university will generally provide you with that and it just says how many nutrients per bushel of corn or per bale of cotton or per ton of dry biomass are moving off the field. That’ll give you a close estimation. You’ll get a range of values. Like if I’m doing research, I can see that a value might be 1.2 pounds per bushel, but we might see 1.1 and 1.3. But that average value is gonna get you close to what’s being removed from the field and then just multiply that by however many bushels you removed and that’s going to tell you how much you’ve actually removed from that field.
[00:20:52] Speaker 4:
Okay. And I have a second question.
[00:20:54] Mike Howell:
Let me jump in before you get to that second question. Von, that’s exactly right. The nutrient removal calculators, that’s telling you what you’re taking off with the crop. We can also have losses in other ways. If we have an erosion event, things like that, we can lose nutrients from the soil in other ways. Those nutrient removal calculators are great at telling you what you’re taking off as far as yield, but don’t forget about losing nutrients in other ways as well. We can lose some nutrients other ways.
[00:21:17] Vaughn Reed:
And even with what we consider to be immobile nutrients, we can still have losses with water. We can just be flushing it out of the system, leaching it out, even though it’s considered to be an immobile nutrient. We can lose it a lot of different ways.
[00:21:29] Mike Howell:
A lot of people don’t realize that potassium can be leached from the soils. I mean, we get down on the Gulf Coast and we lose potassium, uh, with rain events. I’m sorry, go ahead with your second question now.
[00:21:38] Speaker 4:
Is there any way to aid in decomposition to return those nutrients to availability within the soil?
[00:21:44] Vaughn Reed:
Is there a way to aid decomposition of biomass to try and put those nutrients back in the soil? Yes and no. We can aid in decomposing organic matter. We can break that organic matter up into smaller chunks. We can increase the surface area and that’s going to speed up the decomposition of that organic matter. It’s not necessarily going to feed those nutrients back into the soil. That comes down to the carbon to nitrogen if we’re talking about nitrogen or carbon to phosphorus, carbon and potassium. Depends on those ratios, what the percent of how much carbon is there versus how much of that nutrient is there. Those bacteria that are doing the work of decomposing, they have to have those nutrients too. When you have a significant higher amount of nitrogen, so we say a 20 to one if you have less than 20 to one carbon to nitrogen, we are going to see a net return or actually going to have more nitrogen be put back into the soil.
[00:22:35] Vaughn Reed:
But if you start getting up to 40 carbons for everyone nitrogen, the bacteria that are going to be decomposing that are going to be consuming those nutrients themselves and it’s got to go a little bit further through the cycle before it’ll actually become plant available. We can aid decomposition, but unless we are replacing the nutrients that those bacteria are consuming, it’s not necessarily going to return those nutrients immediately back into that soil.
[00:22:57] Speaker 4:
Thank you.
[00:22:58] Speaker 5:
We talked about this a little bit before, but when you’re talking about applying nutrients, most people are going to think granular liquid applications to the soil. What are y’all’s thoughts about, say, foliar applications of fertilizers such as foliar K and cotton? I know there’s a lot of mixed results and stuff on that.
[00:23:13] Vaughn Reed:
Depends on how much nutrients we’re trying to replace. If you need eight to 10 to 12 pounds of potassium to put that crop to the next tier, then a foliar application that puts that out in one application or maybe two applications, if that’s all it takes is that eight to 10 at a really good timing, it works well. We’ve seen this in nitrogen in wheat where you can get a protein boost. So if you have above 12 and a half percent protein, you can actually get a premium when you go to sell that grain. We knew you could go late application of foliar nitrogen and actually drive a lot of that nitrogen into the wheat grain and get that premium. That works really well. If we are 30 to 40 pounds deficient, it’s going to take multiple passes of a foliar application and you’re also assuming that that plant is going to consume it in an efficient manner and put it where it needs to be at good timings.
[00:23:59] Vaughn Reed:
Foliar isn’t going to feed it completely, but it can help in specific scenarios, specifically when you adjust that timing of when you’re trying to put it out. Soil applied is the best foliar in rescue scenarios or in very timely applications.
[00:24:14] Mike Howell:
I like to think of the foliar as kind of like a bandaid to get you through that emergency situation, but the soil applied is by far the best way to get it there.
[00:24:21] Vaughn Reed:
And for nutrients like some micronutrients where we need a very small amount, foliars can work really well because you’re putting that out there, but we’re really limited on a foliar application. Anything above about eight to 10 pounds of KCL or potassium nitrate, something like that, that’s actually gonna start hurting the plant just because there’s so much salt in it. You’re limited by your volume for a foliar and that limits how much nutrients we’re gonna be able to put out.
[00:24:43] Speaker 6:
In times of high fertilizer prices, could banding immobile nutrients offer a greater nutrient use efficiency? If so, could rates be cut? What sources are the best for this and possible application methods?
[00:24:54] Vaughn Reed:
That’s a good set of questions there. Are there placement options for nutrients that actually can increase their efficiency? It’s nutrient dependent. For potassium, banding potassium doesn’t really do a whole lot, but for phosphorus is extremely beneficial. By banding phosphorus, you are putting that phosphorus nutrient, that fertilizer, and a high concentration. And so as the irons, the aluminums, and the calciums are trying to attack that phosphorus and bind it up, you have created an area around that where those nutrients are trying to get in to get phosphorus, but it’s not being able to get into the middle of it yet and get all of that. By banding phosphorus, we can actually increase that efficiency because we’re keeping most of that as available as possible within the season. We’ve seen in Oklahoma and Kentucky and other states as well, you can decrease your phosphorus rates 30 to 40 to 50% by putting it in a high concentrated band, what we generally consider a two by two, so two inches over from the fura, two inches down into the profile.
[00:25:48] Vaughn Reed:
We can decrease our rates 30 to 40% in that manner. It can be liquid or dry. You can do map, you can do dap. Triple superphosphate works well. Dry banding is a little bit more difficult. Liquid products. APP is the most popular form of liquid phosphorus we have, but really anything that has some phosphorus in it does extremely well in a banding scenario.
[00:26:06] Speaker 7:
I’ve heard farmers in the delta grow radish as a cover crop and they believe the deep tap root is bringing nutrients to the surface. Are there nutrient reserves below the root zone and does this bring even a noticeable amount of nutrients up, even if it works?
[00:26:22] Vaughn Reed:
Are there nutrients deep within the profile? Yes, there are. There are lots of nutrients deeper in the profile. That is a fact. The problem is, is the concentration goes down. If we just went outside of Bost here and took a deep profile of the soil, 90% of the nutrients are gonna be within that first foot. 95% are gonna be within the top two foot. And then from there, as you go deeper within the soil, that concentration gets lower and lower. Nutrients start at the top because biomass is breaking down, you grow a crop, you’re growing grass just out on the lawns, that biomass is breaking down and setting up towards the top and then it’s gonna slowly percolate its way down the profile. Crops with the deep tap root, whether it be a cover crop or otherwise, can pull nutrients from the bottom from deeper parts of that soil and bring that up to the surface.
[00:27:04] Vaughn Reed:
Whether that is going to become plant available, it goes back to the conversation about breaking down organic matter. It really depends on this carbon and nitrogen, carbon to phosphorus ratios. If it is high enough concentration of some of those nutrients that it’s going to be mineralized and make its way back into the soil, then that is bringing up usable nutrients that the next season would be possible of being used. If it’s pulling it up and that carbon to phosphorus ratio is not … Italian rye grass is one. Very high carbon to nitrogen, very high carbon to phosphorus. Those nutrients are not going to become available for a longer period of time. It really depends on when you kill that cover crop out and how you’re incorporating it into the profile, whether it’s going to become plant available or not in the next season.
[00:27:44] Speaker 8:
Is there an optimal time from a newer application of Mississippi and row crops, or is it just heavily conditioned dependent? I know a few farmers who applied and incorporated chicken litter in the early spring, but I know traditionally it is applied in the fall due to heavy rainfall in the spring.
[00:27:57] Vaughn Reed:
That’s a good question about timing of manure applications. Is there an optimum timing? In my opinion, I like spring application of all nutrients. I do not like any fall. Lime is, is great in the fall because it gives some time for that, especially in Mississippi where we have fairly mild winters. That lime is gonna react over the winter and we’re gonna get some of that effect before the crop goes in. For all other nutrients, I don’t wanna apply anything regardless of its source until the spring. Nitrogen’s gonna be more available if we plant then. Phosphorus is gonna be less unavailable so we’re not binding it up. You’ve not given it enough a time. Spring application and manure works really well. Obviously, if you get to too high a volume, two, three, four, five tons to the acre, you start having issues with having too much on the surface.
[00:28:38] Vaughn Reed:
But for the most part, there’s not really any issues with spring application of organic matter like that.
[00:28:43] Mike Howell:
The only issue with spring application is can you get in the field?
[00:28:45] Vaughn Reed:
Yeah, that’s the important part.
[00:28:47] Mike Howell:
Logistically, we’ve got to move all the fertilizer products or manure products and get it there and is it gonna be too wet to get in? A totally different concept, but we, we have to consider that as well.
[00:28:56] Vaughn Reed:
Yeah. I realize I work at research and I think research most often. I would love to put every bit of nutrients. I wouldn’t put anything out at planting. I would wait until emergence and then start putting my nutrients out. That’s not practical.
[00:29:07] Mike Howell:
Agronomically, that’s probably the best. Logistically, I don’t know if we can do that.
[00:29:11] Vaughn Reed:
No, no, no. That’s why I understand putting fall applications of phosphorus and potassium. You gotta get out there because, especially as wet as it has been. Now this year-
[00:29:19] Mike Howell:
This year we could probably have done it.
[00:29:21] Vaughn Reed:
Yeah, we could’ve done a lot as dry as it was early on. We had plenty of … We are actually running out of moisture by the time we were trying to plant some of our stuff. This year would’ve been a good year for spring application, but last year when it rained every day for a long period of time, fall application was the only time you could’ve gotten it in before planting.
[00:29:36] Speaker 9:
You mentioned that there’s two types of soil test values for every nutrient. So how does a farmer look at a soil test and decide how much you need to apply or when you need to apply it or just make a decision on that?
[00:29:49] Vaughn Reed:
If you look at your soil test values, if you get a soil sample ran by Mississippi State, if you send it to Waypoint Memphis, you send it to another commercial lab, they should return to you two things. A soil test value You that should say parts per million or pounds per acre of certain nutrients. And then next to it or at the bottom of the page, it should say recommendation. You need to apply this many pounds to the acre. If you get a soil test value, unless you tell them, “I don’t want recommendations,” they’re gona feed you something back that says, “Based on our data, you would need to apply X amount of pounds depending on your crop to maximize your yield.” Just looking at your soil test and making sure that that has that information. If it doesn’t have a recommendation attached to it, I’m biased so I’m gonna tell you to go to Mississippi State University’s extension, you can look up and say, “At this soil test level, Mississippi State recommends,” or if you’re in Arkansas, University of Arkansas, or if you’re in Louisiana, LSU is gona say, “At this soil test level, this is what university research and our recommendations say you need to apply to get here.” Most often, I would recommend if even if you get soil tests and fertilizer recommendations from another lab, compare that back to either another lab or a university or the university to the next state over.
[00:30:56] Vaughn Reed:
Try and compare a lot of those values across to just see this state says this, this lab says this. I can kind of pick and choose, do I have the money for a little more application this year and maybe try and build that up? Or if I’m trying to stick to this university says this is the level I can get away with and move on from there.
[00:31:13] Mike Howell:
Bon, a lot of those soil tests can be kind of confusing for a farmer to read if they don’t understand that really well. I see Dr. Angus catchall is slipped in the back, director of extension here in Mississippi, but there’s county agents around in just about every county and that’s not just in Mississippi, that’s in every state. If you have questions about how to interpret those soil tests, take it by your local extension office. If they can’t do it in the office, they can pick up the phone and find people like yourself to help them interpret those soil tests. Utilize your extension agents.
[00:31:40] Vaughn Reed:
Even if it’s not a Mississippi state soil test, if you bring it in and say, “I’m having a really hard time understanding that, ” if they don’t know it, they will get you to somebody who will know that because that’s what we’re here for. We’re here to help. So I can talk you through, I get emails all the time about, “Here’s my soil test. Tell me what it is and it’s not from us.” And that’s okay. That’s not why we’re here. We’re here to help everyone looking at that.
[00:31:59] Speaker 9:
Also, you don’t recommend fall applications?
[00:32:02] Vaughn Reed:
In a perfect world, spring applications is better. Nitrogen, I would never recommend a fall application. Phosphorus and potassium, I understand the practicality aspect. If you can get out in the spring, I would love to do that. We’ve seen that you can wait pretty late past emergence for corn and soybeans on phosphorus and potassium, wait a little bit into the season and that’s okay. If you can wait till the spring, that’s great. If you can’t, I understand it and realize that practicality, if you’ve got to cover 10,000 acres, covering 10,000 acres in the spring dodging rainfall events is pretty hard to do. My question is about the farmer using heavy machinery in the field. For that reason, is there any impact for heavy machinery in the soil nutrient? Is there necessarily any impact of heavy machinery over fields? For nutrient management standpoint, not necessarily. By taking heavy machinery over the field, especially if you’re running in the same roads you’ve ran every year, you’re using the same AB lines, you’re driving over the same spot, you’re compacting that soil tighter and tighter over time.
[00:33:00] Vaughn Reed:
Now, when we’re doing a lot of tillage, that’s not as big of an impact specifically in the top six inches to a foot where we’re normally doing that. It’s not going to impact the chemistry of nutrient management. It’s mostly going to impact the plant. If we have a really hard layer at three to four inches deep, we can have all the nutrients in the world underneath that, but if the plant’s roots can’t expand and dig through that, they’re not going to have access to it. It’s not going to impact the chemistry. It more impacts the physics of can that plant get through that surface?
[00:33:29] Speaker 10:
Dr. Reed, you’re talking about soil test recommendations. Let’s say you have a very high soil test potassium. I know fertilizer costs are really high this year. Let’s say we get back at soil tests from the lab, says very high recommendation is zero potassium for that acre. Why then would cotton yields go down if a potassium application is skipped for that year?
[00:33:50] Vaughn Reed:
Soil tests, unfortunately, are not perfect. Soil fertility, nutrient management is not perfect. My dissertation, my master’s thesis, everything that I have done shows that soil tests work often, extremely often, above average, but there are some scenarios in which your soil test is estimating a certain value but is actually not telling what all that plant is going to need. If you go to the definition of what a soil test is, it is estimation of plant available nutrients, not this is exactly what’s going to be plant available. We grew some corn, the brown loam research station last year. We grew 300 bushel corn. The soil test value was 160 parts per million or 320 pounds of phosphorus to the acre, which is way above, five times higher than what we would expect to need. And by applying phosphorus, we got a yield bump. There are times in which that your soil test would say no, but it doesn’t necessarily mean that that is going to be perfect.
[00:34:48] Vaughn Reed:
It just means as you go higher above that critical value, whatever your soil test is, as you go higher, your chance of response goes a lot less, not to zero, but a lot less than it was before.
[00:34:58] Mike Howell:
Another thing that could factor into that is if those samples were taken in the fall, there’s a chance you could have lost some of that available nutrients there. I don’t know where the location was that he was asking about, but, uh, if that was in South Mississippi on some of those deep sandy soil, we could have lost some of that potassium during the winter months. A lot of different scenarios that could factor into that.
[00:35:16] Vaughn Reed:
Yeah. There’s a lot of natural fluctuations of soil samples over time, regardless if you’re growing anything or not. Moves with water down the profile, moves with water back up through the profile later in the season as things dry up, more pulling water to the top. So there’s just going to be natural fluctuations, but that’s a good point.
[00:35:30] Speaker 11:
You might have mentioned a little bit about this earlier. We know that soil temp affects sea germination in crops and other plant processes, but does soil temp play a significant role in nutrient uptake and breakdown?
[00:35:41] Vaughn Reed:
Does soil temperature significantly impact nutrient uptake and breakdown? Soil temperature is going to dictate the chemical dynamics of moving a nutrient from one form into another. We used the example earlier of a glass of ice and you’ve got ice cubes and you’ve got water within that. The warmer that temperature is, the faster that conversion from ice into water happens, the same thing with solid nutrients into solution. As that temperature increases, you’re going to increase that flow to a point. It’s not going to exponentially increase the difference between 80 and 90 degrees, let’s just say for soil temperatures, 60 to 70 degrees, that’s not going to double it or anything. But as you increase your soil temperature, you’re going to have faster conversion, not necessarily enough for in season to really tell the difference unless we’re talking about organic matter. As you increase your soil temperature, as you increase your ambient temperature, those bacteria are going to increase their activity and break down nutrients faster.
[00:36:36] Vaughn Reed:
Sometimes we might see an early deficiency of phosphorus or an early deficiency of potassium, but then as that temperature warms up, that organic matter on the surface might break down, put it back into the soil, and then that plant can actually take some of that up. So you might see some early deficiencies that warming up will actually help with.
[00:36:53] Mike Howell:
Hey, great question.
[00:36:54] Speaker 12:
Do you think the soil microbiome approaches will ever replace the corn fertilizer application and are they more likely to be more complementary as a integrated nutrient management perspective? And what do you think are the required steps to take for farmers to adapt soil microbiome, nutrient management aspect?
[00:37:13] Vaughn Reed:
So it’s a multi-step question. Does soil microbiome influence nutrient availability? The answer is yes. Soil microbiome have to break down that organic matter in order for it to become plant available. Then you have the nitrogen cycle or the sofur cycle, which is going to be processing some of those bacteria or going to be uptaking nutrients to break down more organic matter and then releasing some of those over time. For nitrogen, we see the nitrification going from urea into ammonium, into ammonia, into nitrate making its way all the way around. We rely on bacteria to do a lot of this cycling for us. That’s extremely important to have. Could you repeat your second part?
[00:37:48] Speaker 12:
Are we ever gonna replace the current nutrient management with microbiome site completely or do we not need to apply any nutrients at all?
[00:37:56] Vaughn Reed:
If you brought me back moon soil and I adjusted the pH and put enough nutrients, we could grow things off of that. But the cycling of nutrients from taking it up and replacing it back into the soil isn’t going to work as well because there’s not a soil microbiome there. Can we influence that? That’s very dependent. There’s a lot of work being done right now to see if we can introduce a new microbiome and that influence and change the soil and change some of those nutrients up. The problem is that there’s been very limited results on that. Not saying it, that there’s not some good positive stuff out there, but it’s not as easy. Your soil has trillions and whatever is above true and squad trillions amount of other microbiota there and introducing another small amount of a different one, your natives might kill that out within the first couple of hours or worse, your new bacteria might come in and kill some of your others out.
[00:38:45] Vaughn Reed:
There’s still a lot of work to be done on that. I think there could be something that helps a lot of that cycling along, breaking down organic matter on a speedier process, specifically on higher organic matter soils or soils that don’t have a lot of moisture or anything, but there’s still some more work we have to do to figure out exactly where that fits into the situation.
[00:39:02] Speaker 12:
Thank you. I have one more question. So what do you think how long the phosphorous sources are gonna last because they’re getting debated over years and I think it’s gonna be get expensive as we move further forward towards the time. How do you think like in near future around let’s say 100 years or something like that, how hard is it going to be managed fast for us and what can we do as of now from the sustainability perspective so that we can have a better future? Thank you.
[00:39:29] Vaughn Reed:
Mike, do you have an estimation for how much phosphorus we have left?
[00:39:32] Mike Howell:
You know, I’m hearing reports that some of the mines have 40 to 60 years left. There’s some things going on now to help extend the life of those mines. There’s some things like the micronized sulfur technology that nutrient is utilizing that’s supposed to help extend the life of those mines. It depends on where the mine is located, how long those mines are good for. Who knows? We may tap into some new mines and they’re not too far off future. Some of the existing mines, we know the life cycle of those, the lifespan of those, but who’s to say we don’t know about a mine that we’re gona tap into here not too far down the road? I
[00:40:00] Vaughn Reed:
Think I read something a month or so ago about they had just found another fairly large mine on, I can’t remember exactly where it was, but as currently stated, we think we’re gonna run out in the next 100 years, 60 to 100 years. As for how do we increase that efficiency or what can we do to slow that down? I think we’ve done a lot of really good work of understanding nutrient dynamics. So a lot of the water problems we have are nitrate-based, but also some phosphorus as well. Phosphorous can be a big impact on water quality. We’ve made great strides to decrease our phosphorus, leaching, not applying too much. If you are going to apply organic matter, making sure you only apply so much for that. We’ve taken good strides to reduce phosphorus leaching and therefore reducing losses. I think we still have some areas in which we can do better with that.
[00:40:42] Vaughn Reed:
The banding of phosphorus can help a significant amount. We’re decreasing the phosphorus needing to be applied. It also takes some really smart scientists somewhere who know more about it than I do, who can find ways that we can take phosphorus from other sources that are not currently available. We have nitrogen in the atmosphere and we figured out how to take nitrogen from the atmosphere and turn it into fertilizer. We just have to find a way to efficiently and economically pull phosphorus from other areas like the ocean, like water sources, and make that into something that is viable for fertilizer use.
[00:41:10] Speaker 13:
In regards to specialty crops such as cut flowers, we often think in like agronomic terms and these like large scale you need hundreds of pounds. But how can specialty crop farmers that deal in smaller acreage accurately put out what they need when they’re often working in a field the size of this room might be their whole operation.
[00:41:28] Vaughn Reed:
If you look at a soil test, if you’re taking a soil sample and you tell it, “I’m doing cut flowers or maybe I’m growing a specific flour,” most of the time if I grow corn, I’m going to turn that soil test value in and I’m going to tell them corn and they’re going to feed it back into me as pounds per acre, because that’s the scale we’re at. Many times if you go to a lab and you say, “I’m using a garden or I’m doing cut flowers or if I’m doing a lawn,” they’re going to convert that from pounds per acre into pounds per 1,000 square feet. If they don’t supply that for you, then, and I know it’s easy for me because I can just tell you that there’s 43,560 feet in an acre, but you can take a conversion, you can go online and there’s different apps that’ll do it as well that’ll allow you to convert this per acre into this per thousand square foot.
[00:42:09] Vaughn Reed:
If you know the exact size of the area you’re trying to apply, you can even break it down even further and say, “This is how we convert it from 1,000 square feet into 2,500 square feet if that’s the size of your plots.” It is something that I know the numbers in my head what a phosphorus rate or a nitrogen rate looks like on a per acre basis. It takes me a little bit of time to do the conversion to know that 200 pounds of nitrogen in an acre is going to be 20 some pounds in a thousand square foot.
[00:42:34] Speaker 13:
And a second question, when dealing with things such as like calcium, cut flowers need more calcium than most things, how do those farmers need to make sure they’re not getting too much nitrogen to where it doesn’t reproductively bloom and it’s only vegetatively growing while also getting the calcium because often it’s just added in to nitrogen blends with fertilizer.
[00:42:52] Vaughn Reed:
With calcium, that’s one of the things that we don’t normally talk about. I don’t normally speak on is because row crops don’t need a lot of calcium specifically in Mississippi where our soil, unless you’re going peanuts, our soils have plenty of calcium for it. That is a problem with specialty crops, specifically smaller areas where you’re not going out and buying tons, you’re normally going to buy a pre-blend of stuff. You just need to look for another source of that fertilizer. So for calcium, gypsum’s a good source for that. Lime is actually a good source for calcium, but obviously you’ve got something coming out of that, you’re applying lime and that’s going to change your pH around so you have to watch for that. Just trying to select those sources that are more focused on, this has a higher amount of calcium nitrate is obviously a big one, but as you said, you don’t want to apply too much nitrogen because that’s going to impact some of that.
[00:43:33] Vaughn Reed:
So we just have to change our source. Like I said, gypsum’s a really good one and if your pH is a little acidic, we can do lime as well.
[00:43:40] Mike Howell:
There’s also a lot of foliar calcium products out there that you can utilize as well, so.
[00:43:44] Vaughn Reed:
Yeah. Especially for higher value crops like flowers, like gardens and that kind of stuff, higher dollars per square foot.
[00:43:51] Mike Howell:
Guys, we really appreciate all the interaction today. We appreciate all the questions. Listeners, we appreciate you tuning in today. As always, if you need more information on anything we’ve talked about today, you can visit our website, that’s nutrient-economics with a k.com. Until next time, this has been Mike Howell with The Dirt. Listeners, we appreciate you tuning in today. This was a great episode here live at Mississippi State. It’s always great to be back on campus. Did a little check in this morning before we started and this is our 165th episode. When we started this four and a half years ago, I never dreamed that the dirt would be so popular, but thanks to you for cheating in each week and making the dirt so successful. I hate to say it, but today is my last episode as host of The Dirt. The time has come for me to move on and explore the next chapter of my life.
[00:44:36] Mike Howell:
The dirt is still gonna be brought to you each week. Many of the agronomists on the Nutrien team will be back with you each week bringing you new episodes and new perspectives and we hope the dirt will continue to go on as you’ve come to expect it. I wanna thank everybody for your support along the way. It was great to meet all of you at different events down the road. Thanks to everyone who came up and spoke to me at different trade shows along the way. Thanks to each one of my guests who’s helped participate in this and thanks to everyone who’s worked behind the scenes to make these episodes so successful. I couldn’t have done it without you. Over the course of these episodes, we’ve tried to bring you scientific research-based information to help improve the quality of your farm, whether you’re a farmer or an advisor or a teacher, our goal was to give you information to help improve the quality of your farm.
[00:45:20] Mike Howell:
And we tried to do this by bringing you experts from around the world to give you their expertise and share their experiences. We tried to give you something to think about and look at different ideas and different ways of doing things and we hope you learned something, we hope you made you think, we hope you had a little fun and laughed along the way. But until we meet again, this has been Mike Howell with The Dirt. Hey guys, if you like what you heard today, do us a favor and share this podcast with someone else. It could be your neighbor, your friend, your crop advisor, or whoever you think would enjoy it. Your support helps ensure future episodes. So please like, subscribe, share, and rate the show wherever you’re listening from.
