All about cover crops: Lower seeding rates, weed control, advice for farmers & more
Hello, and welcome back to University of Minnesota Extension's nutrient management podcast. I'm Jack Wilcox in communications here with Extension.
Jack Wilcox:It's December, and we're rounding out the year with a discussion about cover crops; what are panelists' observations about plots seeded at a lower rate, cover crops and weed control, and much more. Today, we're joined by three specialists and practitioners with expertise in cover crops. Can you each introduce yourselves?
Anna Cates:Hi. I'm Anna Cates. I'm the soil health specialist with Extension. I work out of Saint Paul statewide.
Ryan Buetow:Hi. I'm Ryan Buetow. I'm a Minnesota state agronomist with the USDA Natural Resource Conservation Service, and I'm based here in Saint Paul and get to work with our our great agronomic practices, including cover crops.
Eric Yu:Hi. I'm Eric Yu. I'm a educator with the crops team, and I am located at the Farmington Regional Office.
Jack Wilcox:And, Eric, you're brand new to the podcast. This is your first episode, so welcome. Ryan, you've been a guest before. It's great to have you back again, and then Anna as always.
Jack Wilcox:Anna, what are your observations around lower seeding rates?
Anna Cates:So your cover crop seeding rate is one of the first and most important decisions you're gonna make about planting a cover crop in Minnesota alongside with species and planting method. So, of course, you know, your rate is gonna depend on those other things, your planting method and your species, but people are continually looking for ways to cut costs with cover crops because buying that seed and applying it is an additional cost, and so lowered seeding rates are of interest to keep the cost down. The other reason people are really interested in lower seeding rates, I would say, is because they're worried about cover crops getting too big. Sometimes we worry about cover crops not getting big enough, like you put that seed out there and didn't get anything for the money you spent on it. But if you're worried about cover crops getting too big because it's more to plant through when you're getting into that spring timeline or it's more challenging to terminate, then people look at lower seeding rates as a way to control that.
Anna Cates:I first heard about this out in the valley where they have pretty heavy soils, and they liked using a really low rate of rye, like 10 or 15 pounds of cereal rye. And this is down from, you know, the recommended rate of 50 to 60 pounds of cereal rye. So it's a lot lower, not just a little lower. But they liked it because they said they got growth. They essentially transformed their field from flat to something with a lot of vertical stems in it, and the verticality of the stems slowed down soil movement.
Anna Cates:So it was really for an erosion purpose, and it allowed the wind to still get in there between the stems and dry out the soil. Again, these heavier soils drying out in the spring is a serious concern. So this is where I started to hear about it, and it seemed like we maybe needed to test whether we really were getting some erosion control at lower rates of cereal rye. So now I've looked at both wind and water erosion at some different seeding rates of cereal rye, the different biomass levels. So, of course, there's kinda two different ways to measure how much cover crop you get.
Anna Cates:One is the seeding rate in the beginning of the season, and one is the biomass level. You can get different amounts of growth from the same seeding rate, or you can get the same amount of growth from two different seeding rates. We can't predict exactly how the seed is gonna respond once it's in the ground. The seeding rate, you can control, but you can't control the weather after that. Anyway, lower seeding rates generally have lower biomass.
Anna Cates:So we looked at wind erosion in western part of the state, and we saw really dramatic reductions in wind erosion, especially over that 2324 growing season. No. Excuse me. The 2425 growing season where it was quite open. Actually, both of those were open.
Anna Cates:Anyway, the the year that we didn't have much snow cover, there was a lot of wind. Even around 200 pounds of biomass, which is not a lot, you're gonna see a lot of bare ground if we're looking at 200 pounds of rye biomass. It dropped the wind windborne sediment movement by an order of magnitude, just hugely less sediment moving around the state or around the the area. So that was one thing, and then we started looking at water erosion and also at nitrate uptake, and those results weren't quite as dramatic partly because when we looked at cover crops planted in 2024 and going into 2025, they all grew beautifully. We, again, had a beautiful season for growing well.
Anna Cates:So planting cereal rye at 10 pounds an acre got us really similar biomass to planting cereal rye at 60 pounds an acre. So we've been starting to say, well, how low can you go? What's a good rate to stop at? And Ryan and I have talked about this quite a bit, so I kinda wanna pass it to you in terms of hearing your thinking about how low is good, how low is too low, how do we decide what a good threshold is.
Ryan Buetow:Absolutely. And so to back up a little bit, when we talk about government programs, right, we have these practice standards. And within that, have technical guidance. And basically, these minimum rates are based on research. Right?
Ryan Buetow:And so we have a wide range of different resource concerns that we're trying to deal with. And, really, it comes down to what is our resource concern. And with erosion, we we talk a lot about percent cover and that kind of stuff, but there's also parts of the state that have to deal with soil nitrate. Right? And so, nitrate leaching.
Ryan Buetow:So we wanna make sure that we have enough biomass to take that up, and there's a lot of studies showing how much biomass is needed, to be able to appropriately do that. And all this really comes back to planting date. Obviously, weather can make a pretty big difference in that, but things like cereal rye are able to really tiller and, kind of expand quite a bit. And so I'd honestly rather see an earlier planting date with a lower seeding rate than an extremely high seeding rate but planted later. Right?
Ryan Buetow:And so, you know, we've kind of been starting to adjust things. We we've focused on cereal rye because it's really the most resilient out of all the different species. It's able to grow basically at 33 degrees, which is really insane when you think about it. So with that cereal rye, you're able to have a lot more flexibility, able to handle a lot more different conditions. And so when we talk about that, we've been slowly moving that seeding rate over time, and I'm probably gonna continue to tinker with it as we move forward.
Ryan Buetow:But this past year, we changed that seeding rates down to 40 pounds an acre if it's planted before October 1. And then after that, made some adjustments based on whether it was incorporated, you know, drilled versus broadcast. Can we even have something in there where if it's no till, 40 pounds? Because with no till, we often have a little bit more of a microclimate that's able to be a little bit more conducive to broadcast success. Right?
Ryan Buetow:So but, Anne, back to your question, you know, that number, it's so it's so hard to really pinpoint that. Right? Because there's so many environmental factors that are gonna influence that. And I think the reality is we we probably could go lower, but we wanna make sure that we're increasing that chance of success for that minimum rate. And so that's why we tend to go higher, especially with programs where, you know, there's dollars accounting for that seed cost.
Ryan Buetow:Because if we're paying for a certain amount of seed and we're putting much less out there, maybe our our payment rate needs to drop down as well. Right? So there's a lot of kind of factors that we consider, but the research is showing that we can get some pretty good benefits from these lower rates, especially at a earlier planting date.
Anna Cates:Yeah. And I would back that up that the the need for reducing night freight in the profile, usually, you need a little more biomass than for erosion. Right now, we don't separate out our government programs by what your precise goal is, so we don't have different seeding rates for those. But it does come down to, you know, who's who's taking on the risk of paying for that seed. If the government is taking on the risk, they have a little more conservative standard of how much you have to seed.
Anna Cates:If it's your risk, you know, go ahead and seed 10 pounds of rye or whatever. It's your money out there, and you can decide whether that got you the benefit you wanted in terms of reducing erosion and not having to clean out your ditches in the spring. Maybe that was a great a great investment for you. But for the government to pay for it, often we want a little bit more certainty that we will get an outcome that benefits society, which includes things like having the ditches open as well as keeping the nitrate out of the water. It's not supposed to be in and all that stuff.
Ryan Buetow:You know, I've seen a lot of different cover crop stands. We have a pretty diverse state. Right? And so there's a lot of things that are gonna influence success. Typically, we have our minimums that we recommend, you know, for payments.
Ryan Buetow:However, a majority of the time, I would like to go a little bit higher than our minimums, right, in order to get that actually good stand out there. But like you said, you know, if all we're worried about is erosion, getting that seed out there is the top priority, what the rate is, and I don't care as much. Right? We wanna make sure that we have something out there that's gonna hold onto that soil and hopefully block that wind from kind of continuing this this cycle that blows everything to Wisconsin. Right?
Anna Cates:Yeah. We don't wanna send our soil to Wisconsin. We wanna keep it. Yeah. So that really the erosion, like I said, can be both a public and a private benefit, but one reason producers sometimes wanna have a higher seeding rate might be for weed control, which is why we have Eric in this conversation because he's our weed scientist expert.
Anna Cates:So, Eric, do you wanna talk a little bit about what you've seen in your research and even in neighboring states too in terms of how cover crops can best be used for weed control?
Eric Yu:Yeah. As far as lower seeding rates go, we really are more concerned about the spring biomass, and it looks like a lot of the research shows that it doesn't really matter what your seeding rate really is. And I know that this past year, at the beginning of this year, Axel Garcia Garcia from Lamberton shared some of his results from a larger project that's funded by LCCMR. And he found that at his lowest seeding rate, I think it I believe it was, like, 25 pounds per acre, seeing no difference when he bumps it all the way up to above a 100 pounds per acre. So a direct correlation between how much biomass you have with cover crops and how much weed control you got.
Eric Yu:But that does come to a point where it does plateau, so you do have to be kind of wary about how much biomass you have before you start taking a yield hit. So there's a balance between the two to get that optimal number. Now that's the number that everyone wants to know. What is the optimal biomass for weed control? And it's been pretty much agreed upon within the Midwest that it's 4,500 pounds per acre.
Eric Yu:The issue with that is in Minnesota, we're not always gonna be reaching those levels, especially if we're just not having ideal temperatures and weather. So I did a research project that tracks all of this, and and it was done in Rochester and Lamberton in 2022 and 2023 where we looked at different seeding rates and different termination timings. And we actually pushed our termination timing back until about the June, just to see how much biomass we can have and maybe that compensation of more biomass, you know, equally more weed control would maybe produce more yield. And so we reached about 4,500 pounds per acre at that latest termination timing in mid June, but we were also getting up to maybe 6,000 pounds per acre at that time too depending on the weather and location. But that does come at a cost.
Eric Yu:When you're delaying it that much and you're delaying your planting as well, you're getting a huge yield hit. So, yes, we're getting really good control at 4,500 pounds per acre, but we're also getting really good weed control at about 2,500 pounds per acre. And that's if we're also assisted with some a really good robust preemergence herbicide program. So cover crops are no silver bullet for weed control. We really have to take an integrated weed management approach here.
Eric Yu:And another comment on cover crops is that we really see those immediate benefits using cover crops. You know, with soil health benefits, we we do have to wait a little bit of time to kinda see those changes right away as far as physically seeing it, but we do see that with weed control. We see it right away, and then we're seeing that right away, then we'll possibly get that soil health benefit, you know, over time, and we'll really see kind of everything coming together. And then a comment on lower seeding rate, maybe I can get some insight with, Anna and Ryan. There's been some research being done in other areas where lower seeding rate is doesn't really matter with the spring biomass, but it does seem to matter with the fall biomass.
Eric Yu:So the lower the seeding rate, the patchier your biomass is, and this is specifically with cereal rye. And that can that can be a little more influential on your erosion side of things. Right? So I'm wondering, are you also seeing that with the research or anything else that you're seeing around your colleagues as well?
Anna Cates:That's a great point. The fault biomass is what determines your overall erosion rate and probably also, you know, a lot of your nitrate uptake. You need to have it well established and have it, you know, ready when the snow starts melting. I'm looking back at the fall biomass we had, and, you know, generally, it's just lower, but there's still not much difference by seeding rate. Only in one of our three sites did we see that, you know, seeding 60 pounds of rye was a lot more biomass than seeding 10 pounds of rye.
Anna Cates:But, again, we had a great fall for growing cover crops. You don't always have that. And you're right, Eric, that you might get a a much patchier stand with that lower rate. I wanted to follow-up with something else you said about that difference between, you know, some weed control at 2,500 pounds of biomass versus really good weed control at 4,500 pounds of biomass. So if you're at that, you know, 4,500 pounds of biomass range, you're you're not skipping those herbicides.
Anna Cates:I'm glad you made that point. And but you maybe are you seeing some delayed emergence to, like, what are the sort of medium kind of benefits that you can get if it's not, you know, your only weed control program?
Eric Yu:Yeah. That's a good question. And I think I wanna first address, potentially, how do cover crops maybe impact weed emergence? And there has been studies that look at how do cover crops impact your most common summer annual weeds. And, when you have adequate precipitation through the year, your cover crops actually don't make a difference in terms of the timing of the weed emergence, but it does matter when it's a drought season.
Eric Yu:So if you have a cover crop down and it is just a drought season, you're not getting much precipitation, you're actually creating an, an environment in that cover crop field where you can actually promote earlier emergence when precipitation does occur. So those rare precipitation events occur, and then the cover crops will actually break the soil down so that you get increased water infiltration, but you also get reduced evaporation just because you have some of that cover. So despite the cooler soil temperature, you still get that moisture level. So because of that, you can get flushes of weeds coming in earlier than if you had no cover crops during drought season. So it's, something to consider in terms of timing your weed management.
Eric Yu:And then as far as, let's say if you're getting lower cover crop biomass in the spring, and you're about to terminate, you really can't skip that herbicide management program. So it's I mean, more often than not, you're gonna be applying glyphosate or Roundup to, terminate your cereal rye at least, and so that's gonna add on to your weed control. And then, there's gonna be your pre emergence program, which is gonna be helpful if you just weren't able to get a good fall biomass established. But on a note of just establishing good fall biomass, you get a head start in terms of competing with your early emerging weeds. Right?
Eric Yu:So your early emerging weeds, they still have to germinate while your cover crops are already, you know, actively growing once they come out of dormancy. So lots of benefits in terms of using cereal rye as far as a weed management tool.
Ryan Buetow:Right. So when you think about organic systems, they've been using cereal rye for for years. Right? And so, I mean, this is a proven thing. It's not, you know, something that we're just finding out.
Ryan Buetow:Cere rye, between its competition and allelopathy, has the great ability to help deal with weeds as a part of an integrated pest management system. However, we gotta be intentional with it and make sure that we're utilizing that tool for that purpose. Right?
Jack Wilcox:What advice would you give farmers who are interested in stepping into cover crops or interested in beginning to incorporate as part of their practice?
Ryan Buetow:There's a lot of different ways to start. Right? So if you're in an area where there's already producers doing this, you know, visiting with your neighbor and seeing what's worked for them, what they've had success with is always a great starting point. If you're an area where there's not many folks trying this, if you have an a problem area or something where you kind of like to play around, you know, possibly try a couple different things. Right?
Ryan Buetow:You know, maybe try a single species cover crop, maybe try a mix of a few different things, maybe try some things that overwinter. The biggest thing is to think about how is this cover crop gonna impact the rest of my system. Right? Do I need to change up my herbicides to make sure that I don't kill this cover crop before it even has a chance to grow? Right?
Ryan Buetow:Do I need to make sure that my nutrient management is being handled in a way do I need to make sure that I terminate this cover crop at a time where it doesn't tie up nutrients? Right? We talk about cereal rye and its impacts on corn. It's not necessarily allelopathy. It's very likely a nitrogen tie up issue.
Ryan Buetow:Right? And so allelopathy in cereal rye impacts very small seeded things. Last time I checked, corn's got a pretty decent sized seed. Right? So, what's likely happening is as that cereal rye gets further and further in its growth, you have a lot more carbon out there.
Ryan Buetow:Right? And that carbon can tie up nitrogen. And there's other nutrients that can get tied up with carbon as well. Right? So there might be some other impacts in that system that are happening.
Ryan Buetow:We talk about sulfur as well. We don't really have some good data on that, but I I would assume, you know, we're seeing a decent amount of sulfur deficiencies out there. Are are we tying things up there as well? Right? So just make sure that you're kinda thinking through how is this gonna impact everything else so that you can get on top of that.
Ryan Buetow:Along with that cover crop, growing cover crops is a skill. Right? And a lot of producers have been doing a great job farming the way that they've been farming for their whole lives. And so sometimes taking up a new skill can come with some challenges. And so if you don't succeed right away, doesn't necessarily mean cover crops don't work.
Ryan Buetow:It just may meaning that you need to make some adjustments. Right? This past year, I kinda took up curling again. I did a little bit in college, but in a league with some friends, and we suck. Right?
Ryan Buetow:And so we're we lost to an 87 year old woman, but she'd been curling for seventy years. Right? And so, it takes some time to learn a new skill. You gotta start to, you know, think about strategy. Think about how are these different things being impacted.
Ryan Buetow:Right? So taking a new skill can take some time.
Anna Cates:Yeah. Don't be afraid to suck at cover crops a couple times, and get some help from your neighbors and from your, from your soil and water district, from your NRCS personnel. All these people want to help you, you know, get better at cover crops, but don't let the perfect be the enemy of the good. If you don't get that, you know, radish as big as your arm or you don't get a a beautiful stand in your first year, there might be some stuff you can learn. You might have struck out.
Anna Cates:You know, I've talked to really experienced cover crop producers, and they also strike out at cover crops sometimes. So I always say, you know, ask questions of those people, and also ask for help from the the cost share program so that you don't you're not losing all on your own dime. We have a lot of resources from the extension service and from the Midwest Cover Crops Council that are recipes and kind of what we think are the lowest risk starting points for cover crops.
Eric Yu:I think Ryan and Nana really covered it well. I I it is a it is a big learning curve, and it does take time to really master everything. And I do wanna emphasize on the cost care share programs. I there's a lot of money just left on the table, and I work in a regional office in Farmington that shares, you know, an office space with SWCD in Dakota County. And I've talked to them, and they they still have money that, you know, they wanna be giving out to farmers.
Eric Yu:They really wanna be incentivizing this practice. Check your local agencies to make sure that there's, you know, ways to cut down the cost risk.
Anna Cates:Yeah. Some of the programs we have this year for people trying to learn about cover crops are the soil management summit up in Fargo. We'll have a lot of cover crop content there. And then I'm gonna run another session at the Cover Crop Academy, which is geared towards agronomists and SWCD personnel to spend a whole year doing a a hybrid virtual and in person class on cover crops. So if you wanna do cover crops and you find that your agronomist can't help you, tell them to sign up for my class.
Jack Wilcox:Is there a particular website that folks should bookmark -an aggregated site that lists a lot of these resources?
Ryan Buetow:There's quite a few different options out there. I would say that the Midwest Cover Crop Council does a great job with their tool, which was just recently updated here. Right? And just to double up on what everyone else has said, absolutely. The agencies, you know, whether it's NRCS or your local SWCD, along with a lot of other organizations, have dollars available right now for these kinds of practices.
Ryan Buetow:And if you've tried cover crops and you don't think it's necessarily the right thing for you, that is completely fine. This is not a silver bullet. This isn't the only way to deal with these different resource concerns. You know, things like crop rotation, reduced tillage can also provide a lot of similar benefits as well, but they can really work well together if you wanna get into those advanced soil health systems. But the Midwest Cover Crop tool has a lot of great resources, information on different species, best times to plant.
Jack Wilcox:Thank you, everybody. And we will include links to these websites in our show notes. So just go ahead and click on this podcast, and you'll you'll get all this information available.
Jack Wilcox:Thank you so much, everybody. That was Anna Cates. That was Ryan Buetow and Eric Yu. We appreciate it very much.
Anna Cates:Bye, Jack. Thank you.
Eric Yu:Thanks, Jack.
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:We'd like to thank the Agricultural Fertilizer Research and Education Council, or AFREC, for supporting the podcast.
