For this edition of Cover Crop Strategies, brought to you by La Crosse Seed, managing editor Julia Gerlach sits down with Jim Stute, an independent research agronomist who’s been studying cover crops since the 1980s.
Stute shares the latest analysis on glyphosate resistant weeds (specifically waterhemp, giant ragweed and marestail), including an on-farm trial that resulted in a 98% reduction in weed numbers.
Stute also discusses the key findings from his graduate study on yield response to different cover crop species.
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Full Transcript
Noah Newman:
Hello, and welcome once again to another edition of the Cover Crop Strategies Podcast. I'm your host Noah Newman, Associate Editor. Before we get started, let's thank our sponsor, La Crosse Seed, solving the soil health puzzle, La Crosse Seed has you covered. Cover crops are an important piece to future profit, but it takes work and it's puzzling at times. La Crosse Seed delivers quality soil first cover crop products, plus training and tools to help you succeed, whether you're looking to grow your cover crop seed business, get product tips, or find a local soil first dealer, La Crosse Seed is ready to help. Learn more at soil1st.com, that's soil1st.com or call 800-356-SEED.
Noah Newman:
All right, this week, Managing Editor, Julia Gerlach, sits down with Jim Stute, an independent research agronomist who's been studying cover crops since the 1980s. That is a long time. On this edition of the podcast, Stute shares the latest analysis on glyphosate resistant weeds, specifically waterhemp, ragweed, and marestail, including an on-farm trial that resulted in a 98% reduction in weed numbers. Stute also discusses some key findings from his graduate study on yield response to different cover crop species. So without further ado, here's Jim Stute.
Jim Stute:
Yes, I am a city boy, I grew up in Madison, Wisconsin, and currently live, for the past 30 years on the farm my dad grew up on. Became very interested in agriculture early on, spending time down here on the farm, and let's be frank, it had to do with equipment operation. And then later on, I got really turned on by biology and realized, "Hey, you know what, agriculture combines equipment operation with biology." So from there on, it was giddy up. Did an undergraduate at UW Madison, started farming here while working an off farm job and flunked out of farming. Went to graduate school based on a key question I had, "I need to cut my input costs, what about this age old practice of green manuring which I saw my grandpa do here on the farm?
Jim Stute:
So I went to an Extension forage agronomist and asked him about that and he gave me a publication, so this is in the late '80s, he gave me a publication from 1973, an Extension bulletin from Wisconsin, that cited data from Iowa in the mid '50s. And I thought, "That's all we got, this is why it opened, so let's work on it." So I went to UW Madison graduate school, both degrees, and studied the practice of green manuring. So we didn't know, in what we call cover cropping now, with legume cover crops. At the time, we didn't know what would work when to plant it. What have you? So we worked out some of the agronomy, we did species screening to find productive legumes that could grow in any number of combinations, interceded with small grains. Seeded after small grain harvest, after canning crops, inter-seeded in corn, which is a totally different environment than we have now, because now with the glyphosate ready trait or glyphosate tolerant trait, we can inter-seed and still get full weight control early on. We didn't have that option. So we had to time it with a short, residual product, and as soon as we thought that the residual was gone, we interceded and it didn't work. So anyway, here we are, things are a lot different.
Jim Stute:
So then, my path professionally was as a county based Extension educator here in Southeast Wisconsin, two different positions and also with the Michael Fields Institute in East Troy, which is a nonprofit dedicated to sustainable agriculture, whatever sustainability looks like. But it's the same practices we talk about is in regenerative, so cutting tillage, cover cropping and diversified crop rotations, that kind of thing. And so, currently I am an independent research agronomist. I am really interested in, well, the issue of economics with cover crops. And I have of the firm belief based on my own experience, my experience talking with farmers and what the social science literature tells us about what it's going to take to adopt and its economics. Purely economics, everyone else is working on soil health and that's good for them, and I think somewhere there's an interface between the two of them, but I'm looking at the bottom line; the impact on yield and minimizing the cost of the cover crop so we can produce a positive return on investment. And if we can do that, people will do it as a routine practice to increase their bottom line.
Jim Stute:
Concurrently, I'm also really interested in the issue of glyphosate resistant weeds. So here in Southeast Wisconsin, we have the big three giant ragweed, which I have a population on my farm, which the university is trying to confirm is resistant. I know from experience with it, if it's not resistant, it's ultra tolerant and it creates a problem; marestail and waterhemp. And not only here in Southeast Wisconsin, but that's also pretty much ubiquitous amongst the states of the upper Midwest. So I'm interested in using the practice of planting green to suppress that.
Jim Stute:
So if you look at more survey data and in particular, the [inaudible 00:05:48] annual cover crop survey, which they've been doing since 2012, the cover crop people say, "We see enhanced weed control our weed suppression. So it cuts our weed control cost." And so I'm trying to put a number on it. And then experimentally, I noticed in one of my on-farm trials, we were forced into a situation because of a wet spring from going from a planned burn down, to a plant grain, terminate later. And I just happened upon the observation that in the plots where we terminated late, the planting green plots, there was no waterhemp, but in the control, which is a no cover treatment, there was waterhemp. Hey, there's something here, something, what the farmers are saying in the [inaudible 00:06:35] survey, let's look at it, let's put a number on it, how much suppression.
Jim Stute:
And sure enough, so I've got a trial that I'm looking at suppression of the big three, waterhemp doesn't show up for whatever reason. So maybe that's just a good reason to do it on my farm. So it doesn't show up. But the point is that we are seeing suppression. And last year, so I've got one year data, not enough to draw firm conclusions from, but in a drought year, which we had last year, we saw 98% suppression compared to the planning green treatment, late termination compared to the control, which is following University of Wisconsin Extension best management practices recommendations; 98% reduction in the weight numbers. Which I think is huge from a resistance management standpoint, because not only do we have fewer weeds that we need to apply a newer active ingredient to, but also the potential for one application per year, so that's less exposure to these individuals. If that works out to be true than this could be a resistance management strategy.
Julia Gerlach:
So just talk about that system a little bit more. So, you're planting your corer soybeans into rye. When are you doing the burn down or when would you be recommending it?
Jim Stute:
So in this trial, it is specific to soybeans. So it's rye planted into corn stalks. And what we're looking at is no cover crop, so we're using cereal rye for the cover crop, no cover crop. And we're also looking at seeding rate, which turns out to really not matter as far as the effect on the following crop. As far as biomass production, yes. Canopy, yes, but not as far as the effect on the following crop. So two different seeding rates, planned burn down before planting, or we plant green and then terminate later. In this particular trial, what we're looking at is very late termination, so it's at anthesis, pollination. And so we've got the two polar extremes of controlling the cover crop; before planting or way at the end. And the reason for the anthesis or the pollination treatment is rye has reached its maximum biomass accumulation, vegetative growth at that point. So we've got the polar extremes. So we're looking at that. In reality, it's probably somewhere in between.
Jim Stute:
So the take home message was we did have weed suppression, but in a drought year because of excess moisture use to get that additional growth that suppressed the weeds, we saw a 30% yield reduction and that is unacceptable. So our next generation study is to look in between. I see. And so I'm going to work on setting that up for next year, stay tuned.
Julia Gerlach:
Okay. Yeah. And you're not doing any roller crimping in this study then?
Jim Stute:
No, there's no roller crimping involved. I've got experience in doing roller crimping, specifically with rye and some other cover crops, just for fun. Buckwheat works great, sun hemp works great, rye, not so much. So do the people that are doing it and doing it successfully, congratulations, because it's difficult getting the timing right. Getting the soil moisture conditions right, so when you crimp it, you're cutting it or crimping it like you're supposed to and you get termination and it stays laid down. My experience is it always stands back up, come do it again, because that was fun.
Julia Gerlach:
Yeah. Well I've heard that there's something very specific about, you have to be able to crimp the inner nodes of the rye at least twice or something.
Jim Stute:
Right.
Julia Gerlach:
And so that would be very difficult, especially with certain equipment. I mean, in some cases, maybe those blades aren't close enough on the equipment or the rye hasn't elongated enough to make that possible.
Jim Stute:
Or the soil's too hard or too soft. So there's definitely an art to it, like farming and a lot of stuff we do. So you got to get the conditions just right. And that's kind of luck also, luck involved.
Julia Gerlach:
Well, it's so interesting to me that you've been studying cover cross for so long. I mean really since sometime in the '80s, you've been studying this. And so, y when you were talking about what you were doing, graduate school, that was your PhD project that you worked on your thesis.
Jim Stute:
Right.
Julia Gerlach:
And were there some specific things you learned from that were surprising to you?
Jim Stute:
There were, and in a very pleasant way, because most researchers, we are advocates. So in my ideal world, every acre would be no-till if soil conditions are right, there are some soil types we can't no-till in sure. But if you're going to go to that extreme to no-till, then let's put a cover crop in because the two were made for each other. And there's a lot of management flexibility that cover crops give you in no-till where the ground is maybe a little slower to dry out with the cover crop. And that's the strategy I used on my farm this year; let's have the cover crop there, watch it. We did have a wet spring, watch the ground. When the ground's dried up enough that I can successfully plant, plant and then terminate the cover crop so we don't have competition with the primary crop.
Jim Stute:
And what I was concerned about was corn. Soybean, to me, that's a no-brainer, but corn, I was a little concerned about it. So what we looked at in this trial, I was interested early on in the nitrogen question. And so, this was when the sustainable egg movement was starting up and they were focused on energy. So the manufacturer of synthetic energy, synthetic nitrogen fertilizer takes an incredible amount of fossil energy. So my idea was to reduce the industrial fixed nitrogen and the energy use with biologically fixed nitrogen. So for my five years in graduate school, I ran a trial for rotational cycles; the cover crop followed by the response crop. And what we were doing was basically looking at response crop, yield response to the different cover crops.
Jim Stute:
And so, we looked at the same five, there was two alfalfa varieties, red clover, sweet clover and hairy vetch. And so, we're looking at yield response and just observations, what works, what doesn't, what are the past interactions, what have you? So of those five, we found that two were consistently the most productive year in and year out. We had some really ideal conditions. We had some wet years, we had some dry years, their performance was consistent. And so, that's kind of a way to look at it from risk management standpoint is we get consistency because cycling and booming boss doesn't do you any good when you're trying to farm for average to make money. So with those two, so it was red clover and it was hairy vetch. The red clover was interseeded with a small grain, the hairy vetch was planted afterwards.
Jim Stute:
And so what we did was look at the synchrony between the decomposition of the legumes, the mineralization of the nitrogen and the uptake by corn. So in and of itself, that's not the full picture; we need to compare that to commercial nitrogen fertilizer. So our treatments were the two legumes, a control zero, so in the zero control, no fertilizer nitrogen, otherwise the rotation and everything was the same as when we grew the legumes. Same rotation, no cover, but then 160 pounds of nitrogen fertilizer, which at the time was for that soil type, the recommendation of University of Wisconsin Extension. So in the cover crops, we measured how much biomass was there, how much nitrogen was in that biomass. So we did that right at planting. We used a technique with residue bags. So we took the samples, we washed them, so we could get an accurate, fresh weight free of soil. We buried them in the residue bags. The residue bags had pores that were large enough that they would allow soil water and the solution with soil bacteria, soil fungi, to have intimate contact with the tissues, but small enough to keep the earthworms and whatever might have carried some of our tissue off.
Jim Stute:
So we buried those bags, concurrently we planted corn and we applied the commercial fertilizer as ammonium nitrate so it was 100% available. Throughout the growing season. And during the first four weeks, we sampled at weekly intervals and then we went to two weeks after that. And so at our sampling time, we dug up some of these bags at different Heights in the profile so that we could see if there was a difference that it'd have to be buried deep was shallow okay. And I should say, this is conventional tillage; I would really like to do this in no-till, but that's another story. We took soil samples to the depth of three feet. So, in the top foot, we went down six inches, and then six to 12, and then from there, second foot, third foot. And what we were measuring there was plant available nitrogen, so any mineral nitrogen.
Jim Stute:
We did some speciation, was it ammonium? Was it nitrate? But just based on budgetary constraints, we grouped it together and said, "This is plant available mineral nitrogen." Concurrently we took corn samples, dry matter samples and analyzed them for total dry matter and nitrogen content. So what we found was, stunning to me and very gratifying, in the case of the legume decomposition and mineralization, we lost 50% of that tissue nitrogen within the first month. The result was a pool of plant available nitrogen in the soil before the period when corn began its period of rapid uptake. So we were building like you do with fertilizer application, building that pool, so when that magic day comes and corn goes from taking up very little nitrogen, to needing one pound per acre per day, we were there, we delivered. So the synchrony there worked very well.
Jim Stute:
In the case of the fertilizer nitrogen, because we applied it in a plant available form right away, there was a spike in availability. So what the legumes did was delay that spike and it's really important from an environmental standpoint, because if we had gotten really heavy rainfall and more than what the soil could hold, it would've leeched; it would've taken the nitrate nitrogen with it. Or if it had ponded, we would've lost the nitrate nitrogen into the air as nitrous oxide. So in effect, what we were doing by delaying the mineralization, we were timely from a corn standpoint, but minimized the potential for environmental risk at the end of the day, no significant difference between the legumes and the full nitrogen rate, but they were all significantly greater than the zero fertilizer, which you would expect. So we put on-
Julia Gerlach:
No difference in terms of yield?
Jim Stute:
In terms of yield. Right.
Julia Gerlach:
That's amazing.
Jim Stute:
Great.
Noah Newman:
Let's take a quick time out, back to the podcast in just a second, but once again, let's thank our sponsor La Crosse Seed solving the soil health puzzle La Crosse Seed has you covered. Cover crops are an important piece to future profit, but it takes working as puzzling at times. La Crosse Seed delivers quality, soil first cover crop products, plus training and tools to help you succeed whether you're looking to grow your cover crop seed business, get product tips, or find a local soil first dealer. La Crosse Seed is ready to help learn more at soil1st.com, that's soil1st.com or call 800-356-SEED. Now, back to the podcast.
Jim Stute:
So at the end of the day, we learned that the legumes released over the growing season, 70% of their available nitrogen. So, that means there's 30% still in the pool, and presumably the easy stuff was mineralized so this is the harder to break down stuff available for next year's crop. We went to three feet again, at the end of the season to see what was left over as far as nitrate nitrogen, which could potentially late, should become an environmental concern over winter. In this case, the exact opposite relationship; the two legume treatments were no different than the zero nitrogen control treatment, which were all significantly less than the full rate of nitrogen fertilizer. So, that's good news. We're in very good synchrony. We met corn's nitrogen needs, it showed up as corn yielded and we didn't have as great a potential economic negative impact at the end of the season. Giddy up.
Julia Gerlach:
That's amazing.
Jim Stute:
It was. So we did this for two years and the two years were distinctly different. 1991, a very hot season, and moisture was just what we needed to get the crop to produce what were record corn yields in the state of Wisconsin for that year, up until it got bumped off the throne, very good growing conditions. The next year, 1992; cold and wet yields were mediocre for the growing season, they were acceptable for the type of conditions we had. But if you look at the relationships and you were to lay this out on a map, they would overlay perfectly. The difference was in the magnitude, so the legumes didn't produce quite the level of the available nitrogen spike. Corn yield wasn't where we were and the corn uptake curve was delayed a little bit because corn development was delayed, but stunning. Two different years, same results.
Julia Gerlach:
That's amazing. And so, you said you were doing this in conventional tillage and basically this was a green manure application, meaning you were incorporating it into the dirt? Into the soil?
Jim Stute:
Something into the soil. It's dirt. Once you get it on your clothes, like it's soil.
Julia Gerlach:
It's dirt under your fingernails.
Jim Stute:
So at the time, and I can't tell you what the research literature was saying, because I wasn't interested in no-till at the time really. So I don't know if there was a difference, but at the time the Extension nitrogen credit said, "Nitrogen credit for terminated forage." So old hay fields or cover crops, you needed to incorporate it to get the nitrogen benefit, the full credit. We now say, that's not the case. The credit is there regardless of tillage system. So, that's good news. That's one of the reasons why I would like to go back and look at it, but a trial like this takes a lot of money. We know it works. We have kind of indirect ways where we can measure it. I would rather spend the limited resources I have looking at yield response and getting people to use covers on more acreage.
Julia Gerlach:
So why is that important to you?
Jim Stute:
Well, so I have a conservation that an ethic that I got it from my dad, and then I was fortunate enough to have Dr. Art Peterson for Soil Science 327 back in the eighties. So Art was one of the early individuals in soil conservation. And he worked as an Extension specialist, but he also taught undergraduates. And so Dr. Peterson and Dr. Burl Lowry, they tagged team and they were both great. And that was my favorite class by far at UW Madison. I was like, "Yeah, we got to take care of our soil, because guess what? They're not making any more of it." Right? Well, so upholder region in another lands, but that takes a lot of work, so nevermind. So we need to protect it and we need to maintain the productivity for future generations.
Jim Stute:
So we've all heard the 9 billion problems; so if past population trends hold true, we're going to have 9 billion people by 2050. And that's not that far off, that we need to feed. And so we can't be stressing our resource that we rely on if we're going to produce food and fiber for them. The other point is there's the issue of climate change. And so, believe it or not, I can tell you the indications of climate change are all around you. We are facing dramatic changes here in Southeast Wisconsin with rainfall, intensities, storm intensities. What used to be a 100 year storm, it's happening a couple of times a month. Come on, tell me something's not going on there.
Jim Stute:
I, as a farmer, look at the difficulty that I have had over the course of my career in getting things done, whether it's windy for extended periods, whether we have really wet springs, really dry springs. I look at the weather conditions on my farm. The last four years are two standard deviations above my long term mean of 30 years, so what that means is so two standard deviations, 95% of the data. So we're on either end, two and a half percent on either side. To get four consecutive years where that's the case. That's a problem. We're losing our top soil, we need to do something about it on our farm, but also we need to do our part to take carbon dioxide, which is one of the drivers of climate change, take it out of play. So we're storing it, sequestering it in our root systems with cover crops with no-till. So I've been doing this so long, I've screwed myself out of carbon markets and ecosystem markets, but I'm still doing it because it's the right thing to do, but it's protecting my farm.
Julia Gerlach:
I want to pivot just a little bit and ask you a little bit more about glyphosate. We've just kind of talked briefly about the possibility of creating resistance in our cover crops to glyphosate, so resistant rye or something else. What are your thoughts on that?
Jim Stute:
So just in general, not that I'm a fan of biotech, and, "Here's the latest silver bullet." We are learning with resistance, whether it's the glyphosate or the corn root worm, [inaudible 00:26:14] that took what three years to get resistance to. There are no silver bullets. So management of pests, it takes an integrated approach. So it's cultural rotating crops, [inaudible 00:26:30] fields. If you see a weed that looks like it made it through an application, get out there and get rid of it so it doesn't produce resistant seed. Varietal selection, just good farming practice. So among my neighbors, I was the first to adopt the glyphosate resistance trait in soybeans because it made no-till soybeans a no brainer. And I used it, I worked at the time with UW Extension. The Extension weed scientists are saying, "This is not a good thing. We are going to develop resistance. So you need to follow best management practices. In beans, where we were somewhat limited with the herbicides that we had, let's use it there. Let's not use it in corn."
Jim Stute:
It developed in corn. They kept saying, "Use it as a defensive trait in corn. We need it in soybeans because the options that we have, have crop health issues." So that's the beauty thing of the glyphosate system in soybean. The soybeans, because of the way the tolerance works, they don't have to metabolize it. So it just knocks out one set of an enzyme from the... It knocks out one set of two. So the trait gives you two sets, so double the amount of enzyme. So we knock out half of it, the soybean plant continues. That's why we have rate restrictions, single application as well as season long so we don't ever overcome that. You can kill tolerant soybeans with glyphosate. I see I've done it. Charging the boom. And it's like, yeah, you sprayed enough and come back in and is dead. Okay. So you can kill Roundup beans or Roundup, yes you can.
Jim Stute:
So no-till beans and frankly, that is our weak link in conservation. It's not the bean residue, but it's losing the corn residue. We need the corn residue because beans don't produce residue for the following crop. It made it easy. So we did it for a number of years. This works good, the university was arguing against it. I piloted UW Extension, had a program called the Two Pass Challenge. So the idea was to put on a pre-emergence service side. And so, the educational psychology was, and they told us this up front, "There's going to be no yield difference. The only difference is you got to make an earlier application. That's putting on the pre-emergence service side, you're still going to put on one post versus post application of glyphosate, versus maybe going in a two post program. At the end of the day, yield's going to be the same." Sure enough it worked.
Jim Stute:
So the problem is Ronald Brady, corn came along, and it's so easy, and crop safety and crop health is there, so why wouldn't I do it? So we developed the resistance, the resistance that's on my farm manifested itself in probably 2018. In 2019, for sure, I was really aware of it. I did everything right; I used the glyphosate trait in corn as a defensive thing. I will spot spray, but I haven't done a blanket application of glyphosate for uniform we control. And I don't intend to. The glyphosate trait is in the corn that I get, because I want the hybrid and I want the drought guard trait. It comes along with it. I pay for it and it's there in case I need it. So we developed it on my farm. I did everything right. It could be because our troublesome weeds, the giant rag, the marestail, the waterhemp, they are outcrossers that pollen could have drifted in from my neighbors and I got the problem. I have to deal with it.
Julia Gerlach:
Yeah. So I am. Yeah. So you called them outcrossers is, are cover crops also outcrossers? I mean, do we have the potential of creating that problem within our cover crops?
Jim Stute:
We do have. So, where I use, I'd like to say, "Ubiquitous," it's not, but that's what everyone is using. So we are setting up a selection pressure with our use of glyphosate to terminate. And glyphosate is the best mode of action for doing that. But we are setting up a selection pressure, and eventually, we could get resistance. So the other, and this is a cover crop that I just love [inaudible 00:31:08] grass works really well as a cover crop. It's got applications, [inaudible 00:31:16] corn [inaudible 00:31:19] corn, for example, or shortly after harvest, it's great. And it's got a different growth habit altogether; it spreads out, so it covers the ground more rapidly than cereal rye does. But we know that we have resistant populations. They've been documented in the research literature forever, and our seed comes from believe it or not, New Zealand, Australia where it's documented. Oh, so our weed scientists here are saying, "Don't do it, no cover crop." And I was like, "Well, wait a minute. Let's watch what we're doing. And be careful. Watch for it. We don't want to lose one tool to keep another one." So it's always management. And so really what this gets to as ag professionals, as farmers, watch your fields, watch for behavior that doesn't look right to you, and if that's the case, let's look at what's going on here and prevent problems from developing.
Noah Newman:
Great stuff there. Thanks to Jim STDY and managing editor Julia Gerlach for that interview. Once again, before we go, let's thank our sponsor one more time, La Crosse Seed. Solving the soil health puzzle La Crosse Seed has you covered. Cover crops are an important piece to future profit for the takes work, and as puzzling at times, La Crosse Seed delivers quality soil. First cover crop products, plus training and tools to help you succeed. Whether you're looking to grow your cover crop seed business, get product tips, or find a local soil first dealer, La Crosse Seed is ready to help learn more at soil1st.com, that's soil1st.com or call 800-356-SEED. Thank you so much for listening, hope you enjoyed it. Until next week, remember for all things cover crops, head to covercropstrategies.com.
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