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Mike Howell (00:08):
The Dirt with me, Mike Howell, an eKonomics podcast where I present the down and dirty agronomic science to help grow crops and bottom lines. Inspired by ekonomics.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.
(00:38):
Well, hello again, listeners. Glad you’re tuning in again this week. It’s springtime here in North America and some of you probably still have snow on the ground and it’s still pretty cold, but planters are starting to roll even as we speak. I know a little bit of corn has already been planted in the US and a lot more will be coming here in the near future. Now, everybody’s probably made their decisions about their different hybrids and what they’re going to be planting this year. Probably the next important decision that everybody’s going to be thinking about is nitrogen and how much nitrogen, how to manage that nitrogen, and we’ve done several episodes in the past talking about nitrogen loss pathways and nitrogen management, but I thought it’d be good to refresh our memory on that a little bit and dig a little deeper into nitrogen management today. To help us do that, we’ve got Dr. Greg Schwab with us. Greg, welcome to The Dirt.
Greg Schwab (01:23):
It’s great to be here, Mike.
Mike Howell (01:24):
Greg, if you will, take just a moment and introduce yourself to our listeners and tell them what you do.
Greg Schwab (01:29):
Sure. I’m Greg Schwab. I have a PhD in Plant Nutrition from Kansas State University and my background is a bit unique. I started out my career as an extension specialist first at Washington State University and then at the University of Kentucky. I was at those two universities for a total of 11 years, and then I made the jump to the private sector and I became the director of agronomy at Koch Agronomic Services. Koch Agronomic Services makes enhanced efficiency nitrogen products. I was there for a total of 12 years, ended up as the vice president of Global Agronomy there and I left that role in August of this year and am now working as a consultant with a group called LVAR Partners. LVAR partners consults with a lot of different companies in the fertilizer space, green ammonia space, carbon space. We’re a group of individuals who all work together on relatively large advising and consulting projects.
Mike Howell (02:24):
Greg, we’re sure glad you took a little time out to be with us today and help us talk about nitrogen. We’ve already talked about nitrogen loss, we’ve discussed that a time or two, but in case somebody’s missed that, if you will, let’s talk a little bit about nitrogen management and give our listeners a little review of how we can lose nitrogen once it’s been applied in the field.
Greg Schwab (02:43):
This is a subject that’s near and dear to my heart. For my entire career, I’ve been trying to help farmers manage nitrogen more efficiently. Nitrogen can be lost really through three different loss mechanisms. Probably the one that most people are most familiar with is leaching. Leaching is when nitrate nitrogen moves below the rooting zone. Not just moves in the profile but goes below the rooting zone of the plant and oftentimes then that ends up in water, either in the groundwater or the surface water, and so that’s the one that makes all the press because of that. But in reality, there’s a lot of places where nitrogen leaching. If you’re in a dry climate, I always joke farmers in western Kansas pray for a nitrogen leaching event because that means the profile is full of water. I’m in Kansas. Leaching is not as big a deal in Kansas as it is further east in the corn belt, so that’s one loss mechanism.
(03:37):
Another one that farmers are probably pretty aware of is ammonia volatilization. This happens when you apply urea fertilizer to the surface of the soil. When that urea first breaks down, it is converted into ammonia gas. It can be lost from the surface of the soil. If it’s not deeper into the profile, it can be lost, and that’s called ammonia volatilization. The third loss mechanism is a mechanism called denitrification, and that occurs when nitrate nitrogen is converted back into nitrogen gas and it leaves as a gas from the soil profile, but it’s leaving as either N2 nitrogen, just two nitrogen atoms, which is 78% of the atmosphere, or is N2O. Those losses happen when the soil is saturated and when there’s not oxygen in the soil profile. Those are the three main loss mechanisms.
Mike Howell (04:27):
Greg, we know we can lose nitrogen these three different ways, but put some numbers on that. How big a deal can leaching be or volatilization or denitrification? I know it’s hard to give a specific number depending on where you are and what the weather is doing. What potential do we have to lose this nitrogen?
Greg Schwab (04:42):
That’s a great question and the answer is like you said, it depends on the weather and it also depends on what you’re measuring as loss. I guess the one I’ll start out with is volatilization. Again, that’s when urea is applied to the soil surface and then it’s converted into a gas and is lost as ammonia gas. That’s the easiest to measure. We can go out in the field and we can put traps that trap that ammonia, and we can measure quite accurately how much of that nitrogen is being lost as ammonia gas. Losses are highest when that urea is on the soil surface for a long period of time without a rainfall or without tillage to incorporate it into the soil.
(05:21):
In those very high loss environments, we can see as much as 30% of the nitrogen that’s applied being lost to ammonia volatilization. However, if a farmer tills the soil or if he gets in incorporating rainfall, maybe two or three tenths of an inch of rain will move that urea deeper into the profile, then that ammonia gas is captured by the soil and losses are quite a bit less.
Mike Howell (05:46):
What about denitrification? How much could we lose from denitrification?
Greg Schwab (05:51):
Is a little harder to measure, so now you’re losing nitrogen as nitrogen gas. If it’s lost as N2, then like I said, 78% of the atmosphere is already N2, a small amount of loss of N2 is not going to be able to be measured because there’s so much nitrogen gas in the environment in the atmosphere. Those are really hard to measure, but what researchers have done is they have over irrigated fields and forced denitrification and then they stop irrigating and let the profile have oxygen again, and then they apply nitrogen fertilizer and say, “Well, how much nitrogen did I have to apply to make up for that event where the soil was saturated?”
(06:35):
When they do studies like that, in Illinois they found that about four or 5% of the nitrate nitrogen that’s in the profile can be lost in each day of saturation. That needs to be saturated, and then you’re only losing the nitrate portion of the nitrogen that’s in the profile, so 4% or 5% per day of saturation. A similar study conducted in Nebraska showed about two to two and a half percent of the nitrate nitrogen was lost per day, so there’s variability depending on soil texture and drainage, but somewhere between 2% and 4% or 5% of the nitrogen that’s in the nitrate form can be lost every day that the soil is saturated.
Mike Howell (07:15):
Greg, that’s a lot of nitrogen that we could potentially lose. It’s obvious we want to do everything we can to keep that nitrogen in the field, not just because it’s the right thing to do and it’s going to protect our environment, we don’t want this nitrogen getting away from us, but that’s going to cost the growers money and they need that nitrogen to make the yield. We have different products out there on the market and these are kind of broken down into different classes. If you will, go through these nitrogen loss management practices and things that growers can do. Talk about the different categories if you will.
Greg Schwab (07:45):
Sure. There’s really a lot of different strategies that farmers can do to try to reduce nitrogen loss and like you said, farmers, they’re businessmen. Every pound of nitrogen that’s lost is nitrogen they paid for that they’re not going to get a benefit from. No farmer wants to lose nitrogen. Nitrogen loss can end up hurting yields too, and that can be even more economically consequential. The first thing that I think we should talk about are products like you asked about, but then I also think we need to talk about other strategies that could be used as well.
(08:17):
If we think about products and we start with ammonia volatilization, then the product that comes to the top of mind is the product with the active ingredient NBPT. That product has been in the market. It was first commercialized in 1999 by a company called AGROTAIN International. That’s the brand name that most people will recognize, but any product that has NBPT at the right concentration is going to do a good job of preventing ammonia volatilization loss from surface applied urea or surface applied UAN since half of UAN is urea. So that’s one product.
Mike Howell (08:52):
Greg, let me stop you right there if you don’t mind. You said something that I really want to point out. You said at the right concentration. Now, we know that there’s a lot of these different NBPT products out there and kind of relate that back to something growers are accustomed to measuring, and let’s just talk about glyphosate. We know we can use a name brand glyphosate and we know how many pounds of active ingredient are in that. If you’re using a generic glyphosate, it may not have as much active ingredient. This is the same thing that we’re talking about with the NBPT. We’ve got to make sure we have the same amount of active ingredient to protect that nitrogen,
Greg Schwab (09:26):
That’s a challenge because unlike glyphosate, glyphosate is a pesticide. There’s labeling requirements for pesticides that you have to state the amount of active ingredient on the label. Since NBPT is not a pesticide, it’s not regulated under the pesticide rules, the labels are not as highly regulated either. Sometimes I’ll see products on the market that’ll have a list of ingredients and it’ll say NBPT, it’ll say the solvent that that NBPT is, maybe another chemical in the jug, and then it’ll say concentration of active ingredients 100%. That’s because they’re counting the solvent as part of the active ingredient and that should be a watch-out.
(10:06):
If you see a product on the market that doesn’t tell you the concentration of NBPT by itself, in my opinion, I would avoid that product. I want to know how much NBPT is in the jug, not that the jug is 100% full. Once you get beyond that, then there is a concentration amount that’s necessary to control volatilization and that amount is about 500 to 600 parts per million once it’s applied to the fertilizer. If you take the active ingredient concentration and the amount that’s recommended, however many ounces per ton is recommended, then just like a herbicide active ingredient, you can calculate the amount of product that you’re putting on to the ton of fertilizer and it should be about 500 or 600 parts per million.
Mike Howell (10:49):
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(11:05):
Greg, appreciate you going through that. I hated to interrupt you, but I knew I would forget that as we went along. You were talking about some different products. If you can, pick back up where we left off.
Greg Schwab (11:14):
Absolutely. That’s the urease inhibitors. If we move to products designed to help prevent leaching and denitrification, it’s really the same product for both of those loss mechanisms. You’re talking about a nitrification inhibitor. Nitrification inhibitors slow the conversion from ammonium to nitrate. That’s important because only the nitrate form of nitrogen can be lost as denitrification or leaching. The strategy is keep the nitrogen in the ammonium form, it’s still plant available, and not subject to leaching or denitrification. Those nitrification inhibitors, probably the one that’s most widely known as nitrapyrin.
(11:53):
Nitrapyrin is the active ingredient and N-Serve and Instinct. It’s been on the market probably almost 50 years, something like that. It’s been around a long time. It’s been used in fall applied anhydrous ammonia quite frequently. I would say most of the fall anhydrous ammonia has nitro or a nitrification inhibitor added, and then there’s some others. There’s DCD, it’s also been around for a long time. DCD is needed at a high concentration relative to the fertilizer. It’s typically pretty hard to get an effective dose of DCD when you’re adding after granulation. Koch Agronomic services has the new product, CENTURO. It’s been on the market for about three or four years now. It competes directly with nitrapyrin with Corteva’s product N-SERVE.
Mike Howell (12:38):
There’s one other category that usually gets associated with these. Was going to ask you to talk about the slow and controlled release products. How do they work and how do they fit into this mix?
Greg Schwab (12:48):
When I was at the University of Kentucky, I did a lot of work with slow and controlled release products, ESN from at the time Agrium but now Nutrien. Those products work by … there’s a polymer that encapsulates the urea granule. The polymer allows water to go in and allows urea to slowly leak out of the polymer. It’s more of a timing type of a mechanism than an inhibitory type of a mechanism. Essentially, think of it as spoon-feeding the crop, so you’re letting a small amount of fertilizer available every day. That helps to avoid conditions like when the soil is saturated, then there’s very little nitrogen in the soil to be lost to leaching or denitrification. It’s a great product and the reason why I laugh is because it’s a product that we actually use at home on the home farm in Ohio on our wheat. We are growing some wheat and some really wet soils and we’ve found that ESN on that wet ground and on wheat is a really good way to deliver nitrogen to that wheat crop.
Mike Howell (13:47):
Recently there seems to be a lot more products coming out. For lack of a better term, we’ll call them biological products that seem to be saying they can actually fix nitrogen in the soil. What experience do you have with those products and nitrogen fixation in a crop like corn?
Greg Schwab (14:02):
That’s a great question, Mike. I think it’s top of the mind for a lot of producers. They see the advertisements going on. I approach these types of products like I approach anything. I look for the research literature that’s published on these products and then try to make a decision based on the outcome of that literature. If you look at those products, there has been a recent publication that’s been put out. It was put out by a group of extension specialists in the north central region and research scientists, I guess, both in the north central region, and they tested several of these products that claim to fix nitrogen. They actually had 61 sites across the north central region of the United States. North Dakota, Minnesota, Iowa, Nebraska. Some of the data came from Missouri, Kentucky, Purdue, Indiana, across the north central United States.
(14:53):
They did study 61 total sites. Not all the sites had all the products. Some of the sites only had one product, but all the sites had products that claim to be adding nitrogen to corn through natural nitrogen fixation or biological nitrogen fixation. When they summarized that data, they found that 59 of the 61 sites showed no response to that biological product. In other words, they had nitrogen response curves, so they did rates of nitrogen with the product and rates of nitrogen without the product, so full nitrogen response curves at most locations, and when they looked at those curves, they could not distinguish the curve that had fertilizer only from the curve, then had the biological product. That’s an important thing to note. How you do the research affects the outcome or maybe affects how you evaluate the outcome.
Mike Howell (15:46):
Greg, the study you’re talking about, we actually had Dr. Dave Franzen on the program last year. He was one of the lead authors on that and he went through that study with us, so glad you brought that back up.
(15:58):
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(16:21):
We’ve talked about a lot of products and some that we know will work, some that we have questions about. If you were a producer and trying to figure out what to do to control your nitrogen, what are some questions you’d be asking yourself to help you make these decisions?
Greg Schwab (16:34):
I’m a scientist, so I would approach it scientifically. I would try to do as much research as I could about the products that I’m considering first. What have other people found? I would try to look for research that’s conducted by a third party, a university researcher, your local retailer, somebody that’s not actually profiting by the sale of the product. That would be the first step. The second thing I would do is try it myself. I’m a scientist so I like to experiment, but I think most farmers do. They experiment with varieties, they experiment with weed control. They should be experimenting with these types of products as well. When you do that, you really got to be careful on how you do the tests. I see a lot of companies that encourage farmers “Apply your normal rate of fertilizer on half of the field and then apply 40 pounds less nitrogen on the other half and add our product and our product will give equal yield to the full rate of nitrogen that side of the field.”
(17:31):
That’s kind of the marketing claims that I see. The challenge I have with that is you haven’t tested whether just 40 pounds less nitrogen would give the same yield. Really, you need to have an apples to apples comparison. I would suggest at a minimum test their product at the same rate as without their product. If you’re going to subtract 40 pounds, then subtract 40 pounds from both sides of the field and then see if their product gives a yield increase. That’s really what you want to know. Does it increase yield when nitrogen is limiting? Then if you want to add a third treatment, add your normal rate of nitrogen and see if maybe I’m just putting on more nitrogen than I needed that year. That’s how I would conduct those trials.
Mike Howell (18:12):
Really good point, Greg. We need to make sure we have that reduced rate of nitrogen in there as well, just to make sure. A lot of growers will bump that nitrogen rate up because they know they have the potential to lose some. One thing that I’ve been noticing a lot here in recent years, Greg, and I’ve been to several meetings this year, and they’re talking about enhanced deficiency fertilizers and a lot of people have the idea that because it’s an enhanced deficiency fertilizer that that necessarily means you can reduce the rate and get the same yield and think that may be the best way to do it. I kind of have a different opinion on this. Yeah, that’s one way to look at it, but just because it’s an enhanced efficiency fertilizer doesn’t mean you have to reduce the rate. It may be letting that plant take up more of that nitrogen or keeping more nitrogen in the field for that plant to take up and raising that yield level up a little more. What’s your opinion on that? Do we necessarily need to be reducing nitrogen rates?
Greg Schwab (19:04):
Yeah, I have both opinions on this. I get asked this quite often. If I’m being asked by the farmer, “What should I do?”, I always ask a few questions first to figure out what type of farmer is he. There are some farmers who really do a good job of trying to do everything they can to control nitrogen loss and then they try to apply what they think is the rate of nitrogen that they need that year. They’re tightly dialed in and trying to do everything they can. If you’re one of those farmers that are on the lower end of the nitrogen application rate, then probably what you want to do is use these products as a risk management tool. You have higher losses than you expect and you’re right on the edge of how much nitrogen that plant needs, then if you have those situations, then you’re going to see an increase in yield.
(19:52):
Other farmers, on the other hand, will apply more nitrogen than they likely need with the thought that, “Okay, I know I’m going to lose some of it and so I’m going to put on 20 pounds more, 30 pounds more nitrogen” and then just realize that part of that is going to be lost. If that’s the type of farmer, so they’re on the high side of the fertilizer application recommendations, then probably they can use one of these products and reduce their nitrogen rates. It just depends on what kind of strategy you’re using, but farmers typically don’t like to buy something knowing they’re going to lose it, so usually it’s the first farmer that I described.
Mike Howell (20:30):
Right. They have to pay for these products and that’s money lost and losing the product is probably the good side of that story. You’re losing yield and that’s what’s really going to come back to hurt you. If you’re losing the nitrogen, you don’t have it there to make that yield.
Greg Schwab (20:45):
I was just going to add a little bit to there. If you think about the cost of a lost bushel of yield, oftentimes these products only cost maybe two or three bushels of corn equivalent per acre to use. It doesn’t take much of a change in yield. Probably even a yield change that’s what we would call not detectable or not significant in a research setting is enough to pay for the cost of these products. It doesn’t take much of a yield change to pay for the product or to justify using the product. If you’re that first guy who’s really tightly dialed in and applying a relatively lower amount of nitrogen and he has more loss than he’s expecting, then he’s probably going to lose enough yield to justify the use of these products as an insurance.
Mike Howell (21:31):
Hey, guys, Mike here, and I want to personally thank you for listening to today’s episode. If you like the show and want to continue hearing it, please like, subscribe, share, and rate it. The future of The Dirt depends on your support. We’ve got plenty of big things coming up this season, so as always, stay tuned.
(21:54):
Switching gears just a little bit, let’s get into politics. There’s a lot of people that are out there pushing to reduce nitrogen. I happen to see something come out, it was last week I saw it for the first time. There is currently legislation in Congress in the state of Nebraska that’s proposing to pay producers to reduce their nitrogen rates. I think it says that they’re wanting to reduce it 20%, and if they can show that they reduced their nitrogen rate 20%, they’ll pay them a minimum of $10 per acre. Are you familiar with this legislation that’s being proposed and what do you think about it?
Greg Schwab (22:26):
I am familiar with the legislation. I live in Kansas, so we’re just right next door. What do I think about it? Whenever somebody starts mixing politics and agriculture, the first thought I always have is a quote from Eisenhower. I don’t know if you know the quote that I’m getting ready to say, but he talked about what he called synthetic farmers. He said these are farmers that live in DC who think that they know better than the farmers who actually farm on how to manage their fields. His famous quote is, “Farming is easy if your plow is a pencil and you’re a thousand miles from a cornfield.” That’s the first thing I always think about when I think about politicians trying to make decisions that are better than the farmer who’s managing the ground.
(23:08):
With that said, I know in Nebraska they’re not a thousand miles from a cornfield. There’s a lot of farmers, I’m sure, and then Nebraska legislature, and they’re trying to do what I think they think is right. The challenge is that what’s right varies depending on where you’re at. If the same thing was right for every farmer, every farmer would farm alike, and that’s just not true. These guys are managing multimillion dollar operations and they’re trying to do everything they can to maximize that return on investment, their land investment, their equipment investment. They’re not doing things intentionally to waste input dollars or not applying more nitrogen than they think they need.
(23:46):
The first thing I would say is that farmers, they’re innovators. They’re going to be trying these products and if they’re profitable, they’re going to use them. In my opinion as a taxpayer, if the practice isn’t profitable for the farmer, I wouldn’t feel good as a taxpayer for my money tax dollars to be invested in a practice that isn’t profitable for a farmer. Let the farmers decide what works and what doesn’t and they’ll quickly adopt the things that do work and add value. That’s kind of my first thought about that. I have other thoughts about this legislation as well.
Mike Howell (24:18):
We would love to hear what you think, Greg.
Greg Schwab (24:20):
They get crazier as they go. Your listeners are going to think I’m a crack pot by the end, but I do try to have scientific basis for everything that I say. I think the next thing you got to think about is how and who is going to decide who the winners and losers are. If you look at this legislation, the maximum is $5 million that’s going to be invested per year, and it mentions a minimum of $10 per acre. You can do the math really quick and say, okay, that’s only about 500,000 acres of the almost 10 million acres of corn that grows in Nebraska, so they’re not going to be able to subsidize a high percentage of Nebraska farmers. What happens when a farmer thinks he’s going to get paid and then the $5 million is up? Somebody’s going to have to decide who the winners and losers are from that perspective.
(25:10):
But then from a product perspective, they’re also going to have to decide, okay, what products qualify? What products don’t qualify? There’s lots of claims being made. Very few of those claims are actually supported in the literature. I did a quick scan. I keep track of biological products that are on the market and I counted in my list 22 biological products right now that have a known nitrogen fixing bacteria within the consortia of the product. Are all 22 going to qualify? Is there somebody going to say, “Yeah, this one does, that one doesn’t”? That’s another challenge is how do you decide, and the bill is pretty silent, just says the Department of Natural Resources will decide. It doesn’t say what criteria they’re going to use or anything like that.
(25:54):
I think that’s a problem as well, and that’s a problem whenever the government tries to subsidize a practice. Let’s say cover crops, same way. Who’s to say what constitutes a cover crop? Sometimes I can plant a cover crop and have zero emergence. I’ve done the practice, I’ve planted it, but it’s not going to be very effective relative to a cover crop that grows and sequesters some of that residual nitrogen. That’s kind of my second thought, and then my third one is really crazy.
Mike Howell (26:21):
Let us have it, Greg. Nothing’s too crazy for us.
Greg Schwab (26:24):
The crazy thing is, as a scientist, I find it hard to believe that people assume that just because it’s naturally fixed nitrogen means that it’s not going to be as susceptible to loss as fertilizer nitrogen. As a lay person, it might seem sensible. “Okay, natural nitrogen fixation, surely that’s not going to go anywhere.” But when I look at the research literature, we have a great plant crop that naturally sequesters, fixes all the nitrogen that needs, and it’s called a soybean plant. If natural fixation was not susceptible to loss, then we shouldn’t see losses nitrate leaching following soybeans. We could look at the literature, which I have to say, “Okay, what does the literature say about nitrogen loss in corn relative to nitrogen loss in soybean crops?” It’s hard to tease those differences out because often soybeans are grown after corn and then corn’s grown after soybeans.
(27:23):
Oftentimes we’re putting fall anhydrous into soybean stubs for the next corn crop and when you see nitrogen loss in the spring, is that related to the soybeans or is that related to the fall anhydrous? Oftentimes it’s kind of hard to tease that out, but researchers have done that, have looked at the contributions, and one of the ways they’ve done it is in the Raccoon River in Iowa. It’s a watershed that’s relatively confined so it’s easier to kind of study than maybe other bigger watersheds like the Mississippi River, and what the researchers have found is that the nitrate loading in the river is actually related or correlates to the acres of soybeans in the watershed. So depending on the price of corn and soybeans, that determines how much continuous corn is planted in the watershed versus how much corn soybeans are planted in the watershed.
(28:15):
What they see is that when there’s a higher percentage of corn in the watershed, then there’s less nitrate loading of the Raccoon River. In the Raccoon River study from 1999 to 2014, so 15 year period, they looked at 60 different locations, sampling locations, in that watershed. Increase in corn acres didn’t increase nitrate loading. In fact, corn acres over that 15 year period increased by 19% while fertilizer applications increased by 24% and yet no increase in the nitrate loading because of those changes. Then the researchers in their conclusion, they wrote, and I’m going to quote this directly because they said it really well, “We conclude that the expansion of corn acres at the expense of soybean acres may be affecting the water quality”. But then they went on to say, “Better management of the soybean in a corn soybean rotation should reduce the nitrate export from the watershed.”
(29:14):
So pretty conclusive that yes, we do have a problem with nitrate leaching and soybeans. Then for Nebraska, I know we’re talking about Nebraska, so I looked up some Nebraska data, and on a very similar study where they were looking at corn grown continuously versus corn in rotation, and what they found was in a six-year study, so they measured had continuous corn for six years versus corn soybean three times, what they found was that the total loss from the continuous corn system over the six-year period was 52 kilograms per hectare. Essentially a kilogram per hectare is almost a pound per acre, so essentially 52 pounds per acre in the continuous corn, while in the corn soybean rotation, they found 91 kilograms per hectare of nitrate leaching, so a 75% increase in Nebraska in highly controlled studies as a result of having soybeans in the rotation versus continuous corn.
(30:15):
To me, as a scientist, I say I don’t believe that just because it’s natural means we’re not going to have a problem. Encouraging biological products like these in corn could be a good thing, reduce fertilizer input, but it may not have the desire consequence on leaching.
Mike Howell (30:33):
Greg, that’s some really interesting information and I am not familiar with those studies. I’m going to have to do some more research on those. Is part of that maybe because the corn plant is more efficient at taking up nitrogen than the soybean plant or what do you see the reasoning behind this?
Greg Schwab (30:46):
I think there’s a lot of good reasons for that. One thing that researchers like to think about is the carbon nitrogen ratio of the residue. When you have a high carbon to nitrogen ratio residue, when the microbes break it down, they tend to use nitrogen from the soil to break down that residue. Corn is a great example of a high carbon to low nitrogen residue. When you harvest corn and you put all that residue out on the soil surface, the microbes start to feast on that, start to decompose that residue, and while they do that, they’re sequestering nitrogen that was remaining in the soil. That tends to tie up to nitrogen.
(31:25):
Soybeans on the other hand have a very low carbon and nitrogen ratio. Microbes see that as candy, if you will. It’s easy to decompose because there’s plenty of nitrogen there, and that decomposition happens relatively quickly and we know that when we grow corn after soybeans, we don’t have to apply as much nitrogen to the corn crop, and part of that is because of that high nitrogen content that’s left over in the residue. I think that’s what’s causing the problem is you have that high nitrogen residue out there and then it gets lost before the following corn plant has a chance to take it up.
(32:01):
From a management perspective, if you’re trying to grow, say, cover crops to capture that nitrogen, cover crops are going to capture probably a lot more nitrogen in corn soybean after soybeans than they will after corn.
Mike Howell (32:14):
Well, we really appreciate you taking time to share your knowledge with us today. I know everybody’s going to get a lot out of this and help them make more informed decisions about their nitrogen management this spring. Greg, do you have any closing comments you’d like to make? Anything you want to leave our listeners with before we sign off today?
Greg Schwab (32:30):
One thing I always encourage farmers is to do on-farm trials themselves. When I was in university, I had small plot equipment. I could really do a lot of replicated trials and measure yield results very carefully, but that was in very controlled environments. The challenge is understanding what happens across the landscape. Farmers actually have the ability to do testing across a landscape. They can do it with their full scale equipment and actually do as good a job and maybe even better job of measuring differences out in their own fields than the university researchers can do in small plot trials. I always encourage farmers “Try products on your own field” and then of course use those products that work really well.
(33:14):
Just real quick, it reminds me of a funny story. One time I was in Kentucky, I was at a farm show and a farmer walked up to me and he said, “Greg, I learned the secret of a 500 bushel corn yield.” He goes, “I’m going to try it next year.” He said, “I walked around this trade show and there was at least 25 products claiming to increase my yield by 10 bushels to an acre.” He said, “I can already grow 250 bushel corn, so I’m sure if I use all these products, I’m going to have 500 bushel per acre corn next year.” We all laugh when we hear that story because it’s not likely going to happen, but that’s the nature of marketing. Oftentimes we see the unusual being marketed as the average when we know it’s probably not.
Mike Howell (33:57):
You also have to pay for those 25 products, and that’s going to affect your return on investment as well, so make sure you’re going to be able to pay for them or whatever you’re putting out in the field.
Greg Schwab (34:07):
That’s true. The key is to try to figure out which few of those products actually do live up to their claims and then use those.
Mike Howell (34:15):
Greg, we really appreciate you taking time to be with us today. We really appreciate your knowledge and listeners, we’ll be back in just a moment with Segment two.
(34:23):
Listeners, I hope you enjoyed the first segment of today’s show. If you did, please take a minute and give us a rating on your favorite podcast channel or app and give us some feedback as well. We want to hear from you to help make the show even better. And don’t keep it to yourself. Please share these episodes with coworkers, family, friends, anyone you think may benefit from the information we’re sharing here. Don’t forget to visit our website, nutrien-ekonomics.com, to help find the latest crop nutrition news and research information as well as market updates, a growing degree day calculator, a nutrient use calculator, a rainfall tracker, and much, much more. It’s all at nutrien-ekonomics.com.
(35:08):
Most episodes of The Dirt are now available for CCA credits. Visit our website and click on the agronomics tab to find these CCA credit opportunities, and if you have a question you can ask one of our agronomy team members, simply ask your question and one of us will get back with you. Thanks for listening. Now, segment two of The Dirt.
(35:34):
Welcome back for segment two, listeners. We hope you enjoyed that first segment we brought to you today. I know I learned a lot from it. We’re in segment two now where we talk about a research experiment station at each of our different universities around the country and across Canada. Today we have Dr. Brian Arnall with Oklahoma State University with us. Now, Brian’s no stranger to The Dirt. We’ve had him on several times and we always appreciate him being willing to share his knowledge and insights with us. We always learn a lot from him. Today, Brian’s going to talk to us a little bit about some of the research going on at Oklahoma State and one of the research farms there. Brian, if you would just take it away and let us know what you have to say this morning.
Dr. Brian Arnall (36:10):
Absolutely, Mike. I always appreciate being on, it’s a great format and I just love visiting with you. I’m with Oklahoma State University. My title is Precision Nutrient Management Extension Specialist, so I hold a three-way appointment in the land grant system. That means I get to do all three jobs. So I’m extension specialist, I teach two classes, I teach soil fertility and precision ag, both senior graduate student level courses, and then I have a 15% research appointment, so I still get to do some research, but most of my research is trying to feed into my extension program and some kind of outward looking stuff too.
(36:47):
I want to share a little bit about our research farm. We’ve got some unique stuff here at Oklahoma State as far as numbers, but Oklahoma is an interesting state. I like to say we run from gators to antelope because our southeast is 300 foot above sea level gets 50, 60 inches of rainfall, then you go to our high plains, which is 4,000 foot above sea level, gets less than eight inches. We do have research stations strategically placed in all corners in central portions of the state that represent our ecosystems, production systems and such. What I want to highlight in this little segment isn’t necessarily a single research station. My predecessors had a lot of foresight and forethought on long-term trials, so the OSU system alone, we have a series of long-terms. They’re all long-term fertility trials, typically N, P, K and some have an S component, that were established anywhere between 1968 and 1972.
(37:47):
Those replicated studies that we have in different corners and different eco regions, and there are four replicates, large trials, we have irrigated dry land. They’re all continuous wheat because in the ’60s and ’70s that’s what we did and we haven’t changed them. We have gone into no-till and so now they’re no-till continuous wheat on about four or five of them that have been no-till for 15 years, and that’s a whole nother data set that’s really cool to look at. We have long-term cotton study, which was established in 1967, and it’s been going as far as an NPK study under continuous cotton down in our southwest region. That’s a really cool study that we can get into look at nitrogen response. It’s helped us build nitrogen response models for cotton. It’s also helped us better understand the nitrogen potassium relationship of a cotton crop and how it’s integral to have both of those team together properly to get good link yield and quality.
(38:52):
Then I’d also be remiss if I didn’t bring up our oldest trial, which is the Magruder plots. That’s a really cool trial that’s in Stillwater. It was established in 1892 when they broke out the prairie. It was a tallgrass prairie. They broke it out and this study established with a single treatment that was unamended. At the time, they didn’t have fertilizer, so it was unamended. Over the years, they added an amended, which was manure, and so they added that. About 1898, 1899, they started putting beef feedlot manure or beef manure on plots and over years that trial added nutrients as they became commercially available.
(39:32):
Unfortunately, the campus was expanding because it started with one building. When they started this trial, there was a single building on campus. Around 1938, campus got so big they actually took this trial, they picked up what they thought was the most six important treatments from what they called trial zero, and they moved it to an identical soil type right outside of campus where it’s been since 1938. While it’s been moved and so some of those long-term trials like to dig on us because we’re not the original location, we do have plots that haven’t been fertilized since 1892. It broke out the prairie and it’s never received fertilizer. We have a plot that’s been getting beef manure since 1998. Then we have a couple other plots that’s been getting commercial fertilizers, N, P and K, and also a lime treatment since the invention of commercial fertilizer.
(40:24):
It’s really cool what we can look at this study as far as, “Man, that check plot, I’ve cut 30 bushel wheat off of this check that’s never received fertilizer.” We found cyanobacteria and blue-green algae that exist only in this plot that’s never received fertilizer, so there’s so much we can get from these long-term. Stratification and nutrients in no-till, it’s just really cool playground for a soil scientist.
Mike Howell (40:49):
Brian, I’ve always heard about the Magruder plots. I’ve been to Oklahoma State numerous times and never had the opportunity to stop by and visit those plots. Maybe next time I’m in town we can set up a few minutes and ride by and take a look at those.
(41:01):
Talk just a little bit about the importance of those not only for the growers there in Oklahoma, but around the world.
Dr. Brian Arnall (41:07):
Absolutely. That’s one of the challenges. Long-term trials tend to drop off, so I want to sidetrack a second. Universities doing a trial every year costs money. To have the students go out or to have faculty go out or technicians go out and plant and fertilize and do all this, it costs money and sometimes it costs a lot of money. We see over time these trials that were established in the ’60s and ’70s, they go away because of financial support. Luckily, we have the fertilizer checkoff in Oklahoma that supports this long-term because our farmers and growers see the benefit. But we learned so much. In the wheat experiments, not in Magruder but in our long-term or ’60s and ’70s, we stopped applying P and K because the rates that were established in the ’70s, we’ve built up our soil test levels so high that we’ve got these really, really high soil tests, so now we’re looking at drawdown. We’re looking at, “Okay, we built them up. What does drawdown look like?”
(42:06):
We can look at varietal response because we hold a variety for five or six years, can look at variety by environment over all the data sets. Going to no-till has been really cool because we can quantify the stratification of organic matter and nutrients even in the check that doesn’t get nutrients. It’s really cool to see a non fertilized check is extremely stratified in the top inch in two inches of soil for carbon, for phosphorus and potassium, even though we don’t put it down. There’s a big deal right now is that how does maybe nitrogen negatively affect our organic matter? We’ve got one trial we have 100 plus, 125 years, but these other trials, we’ve got 60 years of different nitrogen rates and we’ve been able to show that, at least in our environment, it takes nitrogen to make organic matter. In fact, it takes nitrogen above economic optimum to build organic matter at a higher level, and so we start talking about rebuilding our soils, we’re adding carbon, we need nitrogen, it takes that nitrogen to build the organic matter, and it takes a little bit more if you want to build it quickly.
Mike Howell (43:13):
Great information there, Dr. Arnall. That stuff that’s coming to light every day, we need more and more of this information. We really appreciate you joining us today and talking about these long-term studies. I wish we had more of these to draw from around the country, but I understand the cost associated with those. Listeners, we want to thank you again for tuning in today. Here on The Dirt, we’re dedicated to offering the best agricultural knowledge. I’m happy to share that free CEU credits are now part of that offering. Check out the available podcast CEU credits and other learning opportunities by visiting nutrien-ekonomics.com and clicking on the agronomics tab.
(43:51):
Until next time, this has been Mike Howell with The Dirt.
