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Welcome to University of Minnesota Extension's Nutrient Management Podcast. Each month we bring you the latest research in nutrient management for crops and how you can incorporate the latest tips and best management practices to your farm.
Hello and welcome to Advancing Nitrogen Smart, the special podcast series from University of Minnesota Extension. I am Jack Wilcox as always in Extension communications. Today, I am joined by Brad Carlson, Extension educator for Mankato, and Daniel Kaiser, Extension Nutrient Management Specialist in Saint Paul.
Jack Wilcox:Today we'll talk about reducing nitrogen loss using perennial plants. With some of the issues concerning nitrates in water, there's been discussion about adding diversity to the landscape.
Jack Wilcox:Brad, what role do perennial plants play?
Brad Carlson:Well, I think it's important to to recognize we've talked about this a lot, that a lot of the nitrogen loss is sort of an artifact of annual cropping systems that because of the organic matter in our soils and we're mineralizing nitrogen through the growing season, the data really supports that at the end of the season when the crop is more or less done taking up nitrogen, the soil is still warm and we're continuing to accumulate nitrate kinda through, you pretty much through freeze up. It slows down when the soil temperature gets below 50 degrees. And the the dynamics of the loss kinda indicates that that a lot of what we're losing, maybe two thirds of the nitrogen coming through the the tile lines at Waseca, for instance, is attributable to postseason accumulation. And so when we're talking about, for instance, you know, people talk about diversifying crop rotations and adding a third crop, you also have to recognize that if those are annual crops, it's not going to solve a lot. Now that being said, you know, one of the mitigation strategies that we've talked about in the past is, of course, is putting in cover crops.
Brad Carlson:And the issue with cover crops and corn and soybeans is getting those growing early enough in the season that they actually are gonna take up some of that nitrogen and get established and so forth. And so, yes, if you add a third crop, for instance, a small grain and it's getting harvested in August, now you do have a window to establish a cover crop. However, that's, you know, that's that's adding the cover crop is the nitrate mitigation. The crop itself probably isn't helping a whole lot, with the nitrate loss situation. And so, you know, there's been some research and some data that's that's out of Iowa that indicated adding oats to the rotation helped.
Brad Carlson:I think, really, the situation is having the small grain and then following it up with a with a cover crop is really kinda what helps. You know, historically, in Minnesota, we grew oats and then used it as a nurse crop for alfalfa, and then you had the growing alfalfa thereafter that to take up nitrogen and nitrate out of the soil. So that that was a big part of that. You know, beyond that, though, I think, you know, that long crop rotation that we used to have that involved a couple years of corn, then you had small grain, and then you had alfalfa following that. Really, the key in all that was the alfalfa, which is a, you know, a a perennial plant.
Brad Carlson:You know, it's not a forever perennial plant. You know, when alfalfa gets to be seven, eight years old, it dies out. But but it's a perennial for several years. That's really the the what what's made a difference. Some of that that data that was obtained from by Giles Randall and and Dave Huggins was involved in that at the research station in Lamberton, where they had perennial plants at alfalfa, and then they had what was basically native prairie grasses kinda simulating a CRP situation, found that the nitrate loss through the tile lines, when those crops were present went to almost zero.
Brad Carlson:I mean, it was, like, one pound or one and a half pounds of nitrogen per acre per year, which, you know, is about as low as we possibly can get.
Dan Kaiser:Yeah. And Brad's what Brad said, I mean, really, with a lot of this, if we're looking at managing things like cover crops, really, it's it's establishment. And that's really key because the amount of biomass that you have if you look at I'm trying to think back to our our fundamental section, but I think some of the stats we had on there is typically, you know, biomass is anywhere from one to 3% nitrogen. So when it comes to the amount of end taken up, it's really dependent on total amount of biomass out there in the field. There's a balance to that too, especially when it comes to nitrogen management.
Dan Kaiser:Rye is a very good, crop if you can get it established to put on biomass and take up nitrogen. But if you get too much, then it become it can become a problem when it comes to nitrogen management because it actually can start tying up nitrogen. It's one of the things we found with, some of the work I did with Rye, especially in some of the when we're going into situations where cover hadn't been established. I mean, a lot of people will talk about nitrogen recycling, and I just I don't see it. I mean, with that, I mean, if it does happen, it's kind of something that's gotta occur further down the line when you've got establishment over time.
Dan Kaiser:But, you know, if you're looking at reducing nitrate, that may be our best option, when it comes down to it. So if you've gotta put a little extra n on just because of the rye, that might be a little bit cheaper going that route than some of these other mitigation strategies that we talk about, you know, at some point during this this nitrogen smart climb or this reducing nitrate, program. So I think that's really the key on some of this, is really getting something out there at least that's gonna establish, and that's what, there's been some work here at the University of Minnesota looking at some different crop options through the forever green program, looking at, trying to find some other markets for things that can actually be utilized in other ways. Because with the cover crop, you know, you know, typically just killing it off and plowing it down, I mean, you're hoping you get a benefit from the nutrients there, but you're not getting a whole lot else really to recoup the the cost the cost of seeds. So, you know, go ahead...
Brad Carlson:No. I was gonna say, so so the the the concept of forever green, what that really is meaning is always having a crop present out on the landscape. And so even if it's a annual crop, it could be a winter annual crop, it could be a perennial crop that there's always something growing. That that really is, you know, conceptually, that would be a big step towards reducing the amount of nitrate loss from our cropping systems as long as there's some plant growing. Now, of course, really, the issue with that or the crux of that is is what are those plants?
Brad Carlson:Can they grow in Minnesota in our harsh climate? And does it make sense economically? And so I think that's obviously been a big part of what they've been researching for the last decade plus. You know, I I personally, I had Don Wise. He was kind of the the spirit behind Forever Green.
Brad Carlson:He passed away a couple years ago. I had him as a professor, and I remember him talking about some of these concepts already thirty five years ago, when I had him, as an instructor. You know? And and he really kinda got going on some of these. But I I I remember even in those days him talking about the need to get some of these crops to the point where they actually made sense economically that that, you know, we could grow this stuff, but it didn't pay for it.
Brad Carlson:Nobody was gonna do it until it did. And and so, you know, the kinda really the the, you know, what the the the battle plan here is to bet to look at the whole array of things that can be grown and to select the things that they think have the greatest potential, to turn economic. And so, particularly, a couple of the, crops that they've been investigating are winter camelina and field penny crops, which historically was a weed in Minnesota, that that both of these are winter annuals. And so, the idea is is that following a following a a typical annual crop, maybe a small grain that's harvested a little earlier, then you would plant these as sort of a double crop situation in the fall, and then they would be ready to harvest earlier in the spring, as a crop, and then you would come back. And and so, you know, Minnesota, historically, we don't get to double crop like they do in Ohio or Indiana where they'll plant winter wheat and then come back and grow soybeans or something like that.
Brad Carlson:This is a way of potentially pushing that season in Minnesota.
Dan Kaiser:You know, I think one of the challenges really for us in Minnesota is our our planting window is so compressed too, and that's where, you know, I have some concerns with with some of these winter annuals to try to harvest them is whether or not we can get the crop planted in time with with some of these in play. But, I mean, there are some benefits to it. I mean, really clearly, you look at it. You know, Brad, you brought up oats. One of the things I've always kinda wondered are some of these spring annuals, whether or not we could get enough, uptake in the fall because the winter kill, and you have to deal with the biomass in the spring.
Dan Kaiser:But I think some of the data that Jeff Vetsch had at Waseca showed that they really don't do anything. So you've gotta have I mean, these winter annuals are really key. When it comes down to it, if you're not dealing unless you're dealing with a perennial full perennial system, I mean, if you're looking at this forever green concept, it's having something out there that starts growing a lot earlier to take up some of the nitrate. I'm kind of interested. We're starting to do some work on oats, and I know I think some people are wondering about that too.
Dan Kaiser:But, you know, being any sort of annual crop, I just kinda have my doubts we're gonna get enough reduction in the amount of nitrate, in some of these soils. I mean, it might be possible, but it's it's just something we don't know. And, I mean, the other thing then is is too is looking at, you know, whether or not I think, Brad, you've talked about this in some of the other, meetings too is, you know, whether or not they're just certain fields that are contributing more towards, some of the end loss, whether those would be better targets for something like perennials to try to reduce some of that. And that's one of the things you see in the Southeast that we're losing a lot of, with some of the dairy herds dropping is you don't have as much alfalfa out there on the on the landscape. And we know there are clear benefits to it.
Dan Kaiser:I mean, the data has shown that if you look at some of the the water quality data from, you know, Waseca, I think it was Lamberton. If you looked at comparing, perennials versus, you know, annuals, there's a a clear drop off in the amount of nitrate in the, you know, water potential to being leached just because that crop actively growing and starting to grow earlier, have a more developed root system does have a benefit in terms of reducing the nitrate that's in the soil itself.
Brad Carlson:And I think it's also important to you mentioned the the dairy industry. Places in the Southeast, there's producers that I work with who I'm quite familiar with their operations who, for instance, grow canning crops, and then they come in with cover crops. And they're utilizing that cover crop then as a forage. They're they're growing. It's growing in the late summer.
Brad Carlson:It's greening back up in the spring. They're harvesting it as forage, and then they're coming in and planting, corn or soybeans, probably soybeans in most cases because they wanted to, grow a little more in the spring. You know, that that those situations also kinda fit the bill here, but you do have to have the ability to use that forage. And and probably, you're gonna have to be able to take it up and make silage out of it because, you know, the if you're talking about harvesting a a cover crop that greened up and is is growing heavy in early May, you know, we all know what the average weather is like. The odds of dropping that on the ground, drying it, and bailing it aren't real good.
Brad Carlson:So we're probably gonna have to green chop and and put it in the silage. But but that's you know, I I think, you know, we talk about the fact that solutions probably need to be customized towards the operation, and that's really the case like this is if the operation has the ability to manage and utilize that cover, I think that could be a really good solution in some locations. Well, in rye, I think, has really been one of the ones.
Dan Kaiser:I mean, rye, you know, chopped at boot stage. Wisconsin's looked at that for dairy production systems. I mean, I think there's some some opportunities there for some of that. We haven't really researched any of that here in Minnesota. It's some of the thing one of the things I'd like to kinda get on and look at that in a continuous silage system just to see what the nitrogen requirements are because we just don't have a good handle on continuous silage anyway.
Dan Kaiser:But, I think, like I said, as Brad said, there there are some opportunities there. It's just gonna be tailor fit to the system and, you know, whether or not they can find some value in it. I mean, I've seen things certainly I don't know. This, you know, twenty twenty six spring, having a cover crop out in some of these areas wasn't necessarily the worst thing. It's just the amount of wind we had too.
Dan Kaiser:I mean, there's there's other benefits there too that just with soil loss through erosion that that can have some benefits to it. But but yeah. I mean, just the we know there's the clear difference there. I mean, perennial versus annual that you know, annual, we're always gonna expect some system, and the data really bears that out. If, I mean, if you look at incorporating some of these covers in there, we've got a fair amount of data.
Dan Kaiser:I mean, you know, right now with of these annual covers that there could be some benefit if you get them established.
Brad Carlson:The the the 2026 growing year is going to be a real interesting one. You know, as we're recording this and the the growing season has just kinda barely started, there was really good growth of cover crops in Southern Minnesota. So, you know, some years, they barely get established. I know, like, at the research station at Waseca where we've got cover crops on our drainage plots, there was really good growth. And and and so I think really the one of the scenarios that we're going to have to watch, and this is sort of setting up to be a dry year, is if it is a dry year, what what is the impact of having had those cover crops out there?
Brad Carlson:Because it's possible, you know, we know that, you know, that that growing plants, can, take water out of the soil and rob it for the the the crop that you want. You know, that's the whole theory why, you know, Western United States, they they used to follow land is to just simply not have a crop out there and not take the moisture out of the soil for an entire growing season so that it was, you know, conserved for the following year. Cover crops could have an impact on that. And so I guess we'll kinda just have to wait and see how the year plays out this year.
Dan Kaiser:Yeah. Soybeans, I think, are one of the ones that are really affected. I've had some work where you looked at iron chlorosis. We know that an oat companion crop seeded in the spring with the soybeans can help reduce the impact of iron chlorosis. But if you let it go too long, it tends to be more competition.
Dan Kaiser:As Brad said, I mean, water is is another thing too. So they're complex issues when you start including these things in there that you have to to deal with. But, you know, I go back to the point of me before is looking at options. I mean, if we you'd get the situation where we have to look at trying to further reduce the amount of nitrate, I mean, it I think it's probably one of the easier things to do or some of these cover crops versus, some of these other mitigation strategies, that require engineering, especially in in with some of these tiling systems. So there might be some opportunities there that, these things could come into play as kind of a next step to see if we could help meet some of the reduction goals that we're trying to meet, for nitrate across the state.
Brad Carlson:So if you look at some of the data, the Forever Green people have done a little bit of water quality monitoring data. They use suction lysimeters to monitor nitrate concentration in the soil water. This gets a little bit into how the sausage is made, but I think it's important to discuss this because there is data out there being thrown about that is nitrate concentration in water that came from a suction lysimeter. What a suction lysimeter is is like a length of PVC pipe, maybe two feet long. It's got a ceramic cup on the bottom that's glued on.
Brad Carlson:The top is is a stoppered with a rubber stopper. So you've got this sort of airtight tube with the exception of that ceramic cup. And then it's got it's got, plastic tubes going down into them that you can create a suction inside of that, and it draws water into that cup. Okay? So because that water is extracted under tension, that is not necessarily the water the concentration of nitrate that's going to leach.
Brad Carlson:It's gotta be saturated or not under tension in order for it to leach. And so, we do need to be a little careful using suction lysimeter data because, the soil moisture is definitely a factor in how much actually gets lost, and that's typically not measured, when you use that data. That being said, it tends to be useful within a a single study. You can compare different treatments. You know, in the same year, you can sort of compare different sites, but it's really depending on whether those sites have had the similar climate.
Brad Carlson:You know, when we start getting from one year to the next, it becomes a little more problematic. So that being said, the forever green folks do have lysimeter data that shows that that with, with fuel pennycress and Camelina, the couple of the crops that they're investigating, the amount of nitrate in the soil water decreased by, like, 90%. And that's interesting because that really kinda matches the data that Giles and Dave Huggins came up with from Lamberton under those drainage plots. So in in fact, they were even looking at maybe higher than 90%. I think part of the problem with that I shouldn't say a problem with that dataset, but one of the peculiarities of that dataset, and people have pointed this out to us before, is the amount of nitrogen loss under our traditional cropping systems in that study was really high.
Brad Carlson:However, the period when that was measured was nineteen ninety to ninety three, and that was coming out of the drought in the late nineteen eighties. And so we did see major increases in nitrate loss from all of our cropping systems. The data from the Minnesota River bears that out. And so that led to some really high nitrogen losses from crops. I think we've increased our knowledge base and such that we are making better recommendations following a drought, to mitigate some of that compared to what we did forty years ago.
Brad Carlson:Regardless of that, though, the the point really the point of this to that study, though, was that, when they had the alfalfa and the CRP, grasses out there, the amount of loss went down to practically nothing. And so it is it is intriguing that the forever green folks had data that that showed similar effects when they're growing winter annuals. I think another one that that's worth talking about is whether we actually can have a true perennial out there, to harvest for grain. The the the one that they're looking at, intermediate wheatgrass, which has the trade name of Kernza, has been talked about a lot. It shows similar effects, and it is a perennial, and it will root very deeply.
Brad Carlson:You know? But it, like a lot of the other a lot of the other perennial plants that we've talked about, has issues with yield, and so they're continuing to work on that. Like a lot of, perennials, it produces a decent yield when it's first planted, and then it kinda peters out. And so, you know, if we're trying to get the environmental effects of that plant by keeping it out in the landscape long term, we're probably also gonna have to overcome the hurdle of the yield decline that happens over a few years. I know that they're working, diligently on that, but I don't think they've they've come up with a solution to that one quite yet.
Brad Carlson:So if we look at, you know, if you look at where this this whole situation is going, you know, one of the things that I remember, as I mentioned before, I had Don Wise, as a professor forty years ago, which is dating me when I say forty years ago. But, he had talked and that at that time, the whole concept of genetic modification was brand new that we potentially were gonna have to go into genetically modifying some of these plants if we were going to get the kind of increases and benefits necessary to make them acceptable economically and and performance wise. I don't know. You know, it doesn't we really haven't gone very far with genetic modification of some of this stuff, but I do think it is possible that we could, for instance, take some traits. I mean, what you know, why I don't know why we can't take the trait that allows winter wheat to, survive the winter and green back up in the spring and breed it into oats, for instance, or or genetically modify oats.
Brad Carlson:I mean, there's, I think, there is the opportunity to do some of that stuff. Similarly, I think there might be the potential to genetically modify, some of these, other crops like Kernza or or field penny crops or so forth to increase the yield. I guess we just gotta kinda gotta wait and see with that. You know, the big hang up of a lot of this stuff is, that that, you know, organic standards say that you can't have genetic modification and and be organic. And that's been where a lot of the markets are for a lot of these crops so far.
Brad Carlson:And so if they can't market them organically for as an organic grain, then all of a sudden, there hadn't been a lot of market at all. But we're probably gonna have to overcome that hurdle if we're gonna make a lot of progress with it. So I did some math when if we look at the this, you know, roughly 90% reduction in nitrate loss from from putting a perennial in versus having a having a annual crop out there. What I kinda calculated is that if we were going to if we were going to reach the water quality goals that we have in Minnesota, strictly by putting perennials in the landscape, this comes to 6,072,013 acres. Now this is kinda back of the envelope math I did.
Brad Carlson:Obviously, you wouldn't really know until you actually, put it out there and saw how everything was performing. But based on the data I had, that's what I came up with. That's 33% of all cropland in Minnesota. And so is it realistic that one third of all of our cropland in Minnesota gets planted to a perennial? I don't think it is.
Brad Carlson:I do think that we know that the losses, the reductions in losses on our perennials is so significant. It definitely plays a part. But I think the other thing we have to acknowledge is that, we currently have in this state roughly a million acres of CRP. There's a 140,000 ish acres in the CREP program. There's about a 190,000 ish acres in the RIM program.
Brad Carlson:There's about three quarters of a million acres in other set aside programs, primarily US Fish and Wildlife Service easements, for waterfowl production that are also in perennials. That's already there. And so, you know, what I'm talking about needing the the 6,000,000 acres, we're talking about on top of all of that. That's not adding to this because that's already there and represented when we monitor water quality, you know, that that's that's in the mix already. And so, you know, I think that's the hurdle that we're facing when it comes to, incorporating perennials.
Brad Carlson:Now I think long term, I personally do have, some hope that, you know, Dan, you talked about it or said that I talked about it, and I do talk about it a lot, that there could be places in the landscape that are contributing unevenly or more sensitive. I think we we really have a ways to go with identifying, those sites that are closer to water, that have soil types more prone to loss and so forth, where we can target some of these practices. I also think that Southeastern Minnesota, just because of its terrain and and because of some of the issues, really is a good candidate for expanding the, the beef industry, cow calf industry, and potentially looking at getting some more, pasture ground and perennial plants in the Southeast. And I think particularly, you know, if you get closer into the rivers and streams, and places like that would be good candidates. And, you know, at least at the moment, there's decent money in the beef industry also.
Brad Carlson:So, you know, I I think there is the potential to expand the use of perennials in Minnesota. Can we see 6,000,000 acres and totally solve our water quality programs with it? Probably not. But I think it's definitely gonna be a part of the puzzle going forward.
Jack Wilcox:You just heard Brad Carlson, Extension educator out of Mankato, and Daniel Kaiser, Extension nutrient management specialist out of Saint Paul. Thank you both for being here.
Brad Carlson:Thanks, Jack.
Dan Kaiser:Thanks.
Jack Wilcox:Do you have a question about something on your farm? Just send us an email here at nutmgmt@umn.edu. Thanks a lot for listening, and we look forward to seeing you next time.
Jack Wilcox:Advancing Nitrogen Smart is proud to be supported by the farm families of Minnesota and their corn check off investment through Minnesota Corn.