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“Cover cropping is not a one-to-one relationship with increasing yields. It could be better yield stability or resilience over time. It could be reduced nutrient inputs some years. It could be some years that are resilient to droughts or floods, but those are not annual dynamics. Economics can be a real challenging one to overcome for a lot of growers.”
— Steven Mirsky, Research Ecologist, USDA Agricultural Research Service
Like anything in farming, cover crops are not a one-size-fits-all model. Steven Mirsky, a research ecologist with the USDA’s Agricultural Research Service, helped develop the Cover Crop Decision Support Tool, which helps farmers quantify the economic and environmental impacts of cover crops.
In this episode of the Strip-Till Farmer podcast, brought to you by Terrasym by NewLeaf Symbiotics, associate editor Sarah Hill talks with Mirsky about adopting covers with site-specific management, how growers can quantify the benefits of cover crops, how cover crop genetics have improved in the last decade and more.
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Full Transcript
Michaela Paukner:
I’m Michaela Paukner, associate editor of Strip-Till Farmer. Welcome to this episode of the Strip-Till Farmer podcast series. I encourage you to subscribe to this series wherever you get your podcasts. Subscribing allows you to receive an alert about new episodes when they’re released.
Michaela Paukner:
Thanks to Terrasym by NewLeaf Symbiotics for supporting this podcast series. Want to do more in 2022? Now available in convenient planter box application, Terrasym by NewLeaf Symbiotics is proven by Beck’s 2021 PFR to improve yield by 2.7 bushels per acre in soybeans and 4.6 bushels per acre in corn. It also nets $20,000 more in incremental income with every 1,000 acres planted. To calculate your ROI and purchase Terrasym for only $4.35 per acre, visit newleafsym.com/2022. That’s newleaf s-y-m dot com, slash 2022.
Michaela Paukner:
Like anything in farming, cover crops are not a one-size-fits-all model. Steven Mirsky, a research ecologist with the USDA’s Agricultural Research Service, helped develop the Cover Crop Decision Support Tool, which helps farmers quantify the economic and environmental impacts of cover crops. In today’s episode of the Strip-Till Farmer podcast, associate editor Sarah Hill talks with Mirsky about adopting covers with site-specific management, how growers can quantify the benefits of cover crops, how cover crop genetics have improved in the last decade and more.
Sarah Hill:
Welcome to the podcast, Steve.
Steven Mirsky:
Thanks. I really appreciate the opportunity to be a part of your podcast.
Sarah Hill:
Well, to get us started to us a little bit about yourself?
Steven Mirsky:
Well, I've been with USDA Agricultural Research Service now, for about the last 15 years. My formal training is sort of a background in agronomy, soil science, weed management, and that's largely what I do, right? Most of my research program is all focused around integrating crop and soil management and trying to develop more productive and sustainable cropping systems by merging sustainable ag strategies that help with regenerative and resilient properties with precision agriculture that allows for more site-specific management. And so that's sort of been a big component of my research program. And a lot of it is involved with really working in large teams. I collaborate with a lot of folks throughout the region and nationally to kind of develop these solutions, so that we can sort of break down how climate and soil management come together to drive productivity and the benefits we get from kind of a lot of our sustainable ag strategies.
Sarah Hill:
Okay. So let's go ahead and jump right in to talking about cover crop research. So you lead more than a 100 researchers in 29 different states in cover crop research projects. Can you give us an overview of what all of these different researchers are studying?
Steven Mirsky:
Sure. This kind of started out as a small group of us that were in the east coast. And we started to develop a number of regional collaborations to get that sort of morphed into developing sort of more of a national collaboration with a non-farm research network. And so we moved a lot of this kinds of research questions that we're doing on stations, on farm and working with farmers who are engaging cover crops in a whole host of ways, right? Some are working with mixtures, some are just using cereal covers, some are killing them late or killing them early.
Steven Mirsky:
There's a range of performance on all these farms and we're sort of working with this farmer network to quantify how cover crops are influencing water and nitrogen and weeds, insects, disease, and a host of different other features like economics and trying to put that all together to then build kind of insights and models that result in decision support tools that we you make available through web-based applications, so that these tools or recommendation systems that allow growers to make decisions in the near to real time, all the way to more long term planning around cover crops and management.
Steven Mirsky:
And so the big effort that we do is primarily focused on short term return on investment. Right? We're not setting up long term cropping systems experiments on farm or on research stations in this big network that we're describing here that are doing the same practices on the same fields year in, year out. We're really looking at sort of mature cover croppers or people who have a long history of cover cropping on their research farms or on their production farms that are looking at the short term implications of not cover cropping. So how does having the presence or absence of a cover crop in that field in any one year influence a host of sort of the annual management concerns around your water, your nitrogen, your weeds and so on.
Steven Mirsky:
And so we've been getting this large kind of network together through a bunch of different funding mechanisms that are both in the public sector, as well as in the private, we've developed a lot of private partnerships with agribusiness, as well as technology companies and private on farm networks and commodity boards to sort of come together in this collaboration around merging cover crops, which we sort of fit in a spectrum of different sustainable ag strategies into a more precision framework by really understanding how it works out across a wide range of climates and soils.
Sarah Hill:
Well, that's fantastic. So you come kind of alluded to this in your previous response, but I'd like to pinpoint it a little more thoroughly. How can growers quantify the benefits offered by cover crops in their operations?
Steven Mirsky:
Yeah, that is a great question. And certainly the question of the day and the dissatisfying answer that a scientist often give is, it depends, right? It's all of the factors and the benefits of cover crops are very regional and site specific. The benefits that a farmer might be targeting in the State of Iowa is often different than what they might be targeting in the State of Maryland or North Carolina. And so a lot of the benefits that we get from cover crops are first and foremost, objective driven, right? What is the objectives of the farmer? How are they managing the covers? What species do they select? That really drives the types of benefits they get.
Steven Mirsky:
For us, we've seen plenty of in the short term, real kind of immediate benefits when it comes to providing some weed suppression. Certainly there's been a strong body of literature to support the benefits on recycling nutrients and preventing erosion. And I think where a lot of folks are interested in is, how much nitrogen should I get from their covers. And that really depends on their farming practices, their systems, their climates, their soils. And then of course, the end goal is yield. And the problem that we have so much with yield is their yield is affected by so many factors, right? There's just so many production factors that affect corn yield in a given season or a soybean yields, or whatever your crop is, that it's hard to equate one specific practice to a return on yield benefits annually. We have certainly seen in many cases, yield increases or no differences of yield and in some cases yield lags, and that's a very long complicated answer that depends on a lot of factors.
Sarah Hill:
Fair enough. So with all of this research happening, what are you finding are some of the current gaps in the knowledge that's out there about cover crop breeding?
Steven Mirsky:
Oh, wow. That's a great question. Well, I think that we're seeing a resurgence in cover crop breeding now that has not been in place for a while. There was a lot of work done historically on cover crop breeding. And there was a lot of materials developed a long time ago, but we've spent decades not seeing really big improvements in a lot of the material that we're using now, that is sort of part of the mainstream available cover crop germplasm, and not a lot of that material has seen a lot of it improvement.
Steven Mirsky:
And so when a mature breeding program that's been around for a very long time, there's a lot more resources that have to go into seed modest improvements in the germplasm, whereas cover crops that have to receive a lot less genetic improvement for the targeted of interest, right? We have many cover crops that are used in certain cash crop applications, but they've been bred for that application. Right? Versus if you're using it for a cover, there's different traits that you're looking for.
Steven Mirsky:
And so what's pretty exciting about cover crop breeding now, is that just getting together small breeding programs that can make big progress in a short period of time, just because of the lack of attention that it's been given. And so I'm really proud to be part of this group. Our name is evolved over the years, to cover crop breeding network or a national cover crop breeding network, but it's a group of public sector researchers and some private sector, seed and industries that have worked together around developing new cover crop germplasm. And this is a distributed network that's across all of the US, and we're regionally adapting, cover crop lines for a number of traits of interest.
Steven Mirsky:
And so I think it's a really exciting and growing area. We've been in place for our closest seven years now. And we're releasing certain [inaudible 00:09:44] hairy vetch. We have a predominantly a major legume breeding program of hairy vetch, crimson clover and winter pea, but we are also starting to do some breeding in cereals, particularly cereal rye for increased allelopathy. So I think that just even a short period of time, we've already been able to see some big improvements in our materials that we're hoping to release soon. So I think that it's a ripe area for lots of scientists, or breeders to get involved and really get more sight specific in regional in the germplasm that's out there.
Sarah Hill:
Okay, great. Well, that kind of answers the next question I had, which was talking about how cover crop genetics have maybe improved or changed in the past five to 10 years, have there been many other advancements?
Steven Mirsky:
Yeah. So the main target for us was to develop more winter hardiness in legumes, to be able to see greater adoption of legume cover crops further north, you see a fair bit of use and adoption of legume cover crops in the southern components of the US. But as you get further north, they're really struggling to get integration for all the reasons, right? They're not fairly winter hardy. You need to get them in earlier just to get good performance. And so there's a lot of constraints.
Steven Mirsky:
So the main breeding program has been around developing winter hardiness, but then we also have some cover crops that we know farmers are concerned about the weediness of those cover crops, like hairy vetch and how they have a hard seeding. It can persist in the seed bag. So we've been also screening material for soft seeded hairy vetch lines, we've explored hard and soft seated crimson clover lines. And then there's been a big emphasis around disease resistance in winter pea. So those are the main traits in the legumes. And then as I mentioned earlier, the trait that we're targeting with cereals is increased a little earthing.
Sarah Hill:
Okay. So has your research evaluated the impact of cover crops on herbicide resistance?
Steven Mirsky:
Yeah. You see a lot of excitement in the herbicide resistant management community, both from the researchers, I think you see a lot of incentivizing programs to get folks to adopt cover crops for purpose, right. Is that, if it's a real win with a big impact in the short term, right? Like you can make a big impact on a number of the weed species that are really problematic, that are greatly affected by having cover crops in the fields. The cover crop when it's living, so a cover crop is living that's certainly when it's most competitive against weeds. So certainly if you're looking at a winter annual cover crop, like cereal rye, fall growth can be really impactful for biennial weeds or problematic weeds, like [inaudible 00:12:52] will be impacted by having cereal rye out there.
Steven Mirsky:
But then also then when you've killed that cover crop and leave it as a mulch in the field, we've seen big impacts on reducing weeds, making them have lesser population densities in the field, but then also potentially interacting with herbicide programs that have synergy to have greater suppression. But at the very least we are seeing a significant impact on a number of our big problems, herbicide resistant biotypes like different pigweed species, for example.
Sarah Hill:
Great. So in the research that takes place across so many different states, what are some of the differences in how growers are using cover crops between the different geographic areas?
Steven Mirsky:
I think that, as I mentioned earlier, you see the general pattern that certainly, as you get further north, you see less and less use of legumes. You do see, as you get further south, a lot more diversified cover crop mixtures, just because the legumes in Nebraska's will do better in some of these colder climates. So the climate is a big driver of it all. Like how big of a window of an opportunity do you have to get the cover crop in and how hard of a winter do you have has been so sort of a big impact. And so we do see that sort of separation from mixtures and certainly an emphasis on bigger legumes.
Steven Mirsky:
And then I'd say that moisture gradient is the other part of what we see a big trend differences on, right? We see, where regions that have higher soil moisture and precept that's coming to the growing season, or that are expected to during kind of that critical time for the cash crops. You do see more and more folks delaying the cover crop termination, trying to either delay it, close to planting, or even planting green. We see more of a trend with those folks to maximize the value and the benefit of the cover crop and some of the services that you could get, because they also have the water there to support that growth. And we see big differences from the mid Atlantic region to southeast or south central all the way as you get to out to north central and go west, those moisture gradients have big impacts on the duration of time that folks are leaving the covers in the field, and then whether or not they're going to explore or work with planting green options.
Sarah Hill:
Okay. So have you seen anything about how the lushness of that cover crop in different parts of a field might affect the soil nitrogen levels in different parts of the field?
Steven Mirsky:
Yes, absolutely. So in agriculture, this is always our challenge, right? Is that we don't have this uniform field. Most of our fields are highly spatially variable. We often have a lot of topography in our farm fields, and that creates micro drainages, that you can have wetter areas and dryer areas, and that will have impact on the growth and development of the cover crop, as well as you can have hotspots of fertility organic matter and fields. And so of these are sort of influenced by a number of factors, but topography is certainly a big one of those. And so that will give you spatial variability in your cover crop performance. And so that, you could easily see in a field spots where you have like just 300, 400, no pounds per acre of biomass all the way up to three to 4,000 pounds per acre biomass, those are huge ranges and performance of the cover.
Steven Mirsky:
So that's going to have big impact on how much nitrogen it's scavenging, first of all, in the fall and early spring when it's growing, but also can have implications on the nutrients that are released from that cover crop, as well as obviously impact on the water dynamics and the weed suppression, right? So all of these kind of benefits of covers that really come from having a bigger cover crop, those extreme differences in the fields is what creates really big problems for just having a uniform management. And so we're really advocating and hoping that we can continue to provide a role in mapping cover crop performance in the fields and giving high resolution maps of that spatial performance so that it can then help growers with putting their inputs out in a variable way, right? So applying their crop populations or fertilizers or herbicide programs differently across the field.
Michaela Paukner:
Before we get back to the conversation, I’d like to thank our sponsor, Terrasym by NewLeaf Symbiotics, for supporting the Strip-Till Farmer podcast series. Want to do more in 2022? Now available in convenient planter box application, Terrasym by NewLeaf Symbiotics is proven by Beck’s 2021 PFR to improve yield by 2.7 bushels per acre in soybeans and 4.6 bushels per acre in corn. It also nets $20,000 more in incremental income with every 1,000 acres planted. To calculate your ROI and purchase Terrasym for only $4.35 per acre, visit newleafsym.com/2022. That’s newleaf s-y-m dot com, slash 2022. Now here’s Steven Mirsky once again.
Steven Mirsky:
Oh boy, that's a big one. So obviously the economics of cover crops is it plays a huge role. And there's a fair bit of evaluations from socioeconomic reports that have come out over the years to emphasize that it's not just economics. There's a lot of factors that drive adoption with the complexity that goes into management, it introduces more complexity. So it's more cognitive burden, things that to have to deal with, right? There's a lot more moving parts in the system, and that complexity can build fatigue. And so that's another a reason.
Steven Mirsky:
But we've certainly tried to focus on all of those things, right? We're trying to focus on the simplicity of management. We've tried to focus on making it more economical. It's an additional cost in the system. And the realities of it is that it's not always going to have a return on investment economically, right? Cover cropping is not a one-to-one relationship with increasing yields. It could be better yield stability or resilience over time. It could be some years reduced nutrient inputs. It could be some years that are resilience to droughts or floods, but those are not annual dynamics. And so economics can be a real challenging one to overcome for a lot of growers.
Steven Mirsky:
And what certainly we've seen, like I'm in the State of Maryland where there's a cost share program. So we have tremendous adoption and use of cover crops because of state-based incentive programs. And we are seeing more and more private industry and the federal government incentivize more and more cover crop practices, which helps take some of that economic burden off. But I guess I made the point that economics is certainly a key challenge, management complexity is a key challenge as well. So I think those are sort of the two big ones.
Sarah Hill:
So how can cover crops enable growers to maybe plant earlier during some of the unusually wet springs that we've been having in the past few years?
Steven Mirsky:
Yeah. So cover crops are doing two things in the spring, right? They're using water, they're transpiring. And so there is that water use helps dry down that soil some. And so having something growing at least get some moisture reduction in the soil to help enable to get into the fields a little earlier after rain events. What it's also doing though, when you have a well established cover crop is those roots and those crowns are often creating a rigidity there that is sort of a buffer against the compaction that can happen from tires tracks and from the field equipment. So that even if that field is a little wetter than that you would want to go into a bear field because you have this sort of matte there, that's helping to reduce some of the compaction of the equipment. It helps you give a few more workable days.
Steven Mirsky:
And there are a number of folks who have been calculating this. I kind of am eager to see where that is playing out across the country. And there's going to be probably really good information coming out about that in the next year or two, because there's a lot of people studying that, but it's certainly been, a lot of what we've seen is this ability to both dry down the spring dynamics faster, but then also create a little resistance to compaction.
Sarah Hill:
So kind of on the other side of that coin, how do cover crops help increase the drought tolerance of cash crops?
Steven Mirsky:
Oh, I love this question. This really is something that our team is doing really well. So the precision sustainable ag network has an extensive distributed network of water sensors, all across farms throughout the eastern half of the US and on farms that have big strips of cover crop and no cover crop. And so we're monitoring the rates of water infiltration and storage, and we're doing a range of different management. So farmers are allowed to manage the are cover, however they want. They can have small covers, big covers, mixtures, monocultures, and killing it early, killing it late, so to speak. And we're able to track any one rain event and how it behaves in those systems, the presence or absence of a cover crop.
Steven Mirsky:
So if you have a cover crop there, versus you don't, one of the things that we're seeing is that it can greatly reduce the compaction that sort of comes from a rain event, right? When a hard rain can come in hard and fast, it can sort of smear the surface of the soil and compact the surface of the soil a little bit, that end up resulting in more runoff of that water and less infiltration and storage. And so their cover crop sort of acts as this energy reducer, so to speak from the gravitational forces that are coming from raindrops, right?
Steven Mirsky:
And so early on in the season when the cover crop is growing, sure that's using water, but once a cover crop is terminated and it's got that service cover before the cash crop canopies, so like some point in the four to six weeks after planting your cash crop, it's going to completely canopy. And it'll sort of provide that same result, with when the rain falls. But early on, when that crop has in canopy, you've got this cover crop mulch there, that's sort of increasing the amount of water that infiltrates its stores in the soil.
Steven Mirsky:
And so if you're going to go into a droughty summer and you've got this nice mulch that's been helping with reducing the runoff, you've sort of banked more water into that system. Plus by having that surface mulch there, you've also are keeping the soil temperatures cooler, you're preventing the sun from sitting right on that soil surface. And that in itself has a huge benefit in reducing sort of your evapotranspiration rates as well. So there's sort of a number of ways that cover crops can increase water infiltration and storage going into what we would generally find as the drier part of the year, the summer. So you're sort of banking a little bit more water.
Steven Mirsky:
Now, it really depends on the climate, whether that's a net gain or is it just a zero-some gain, or is it a net negative? If you're in a region that has a really dry spring and you're growing a cover crop and drying down your water, the bolt of that cover crop might not really ever get you right in increasing water infiltration and having that kind of drought resistance in the summertime. But if you're in regions where you tend to get it decent spring moisture, and it dries up into summertime, which is what is a lot of the climate models are suggesting, which is wetter springs drier summers. And we've seen a fair bit of that, you're going to end up seeing a lot of times where that cover crop is giving you that net of benefit in the summertime of overall water storage in the soil profile. I know that's a long answer. I'm sorry it took a while to get out, but that [crosstalk 00:25:51].
Sarah Hill:
No, that's great.
Steven Mirsky:
Yeah.
Sarah Hill:
So kind of building on what you were just talking about, how does climate interact with cover crop management and growers cover crop decisions?
Steven Mirsky:
No, climate is everything, right? The farmers are constantly doing this multiple variable analysis in their heads all the time about what they're going to do and when they're going to do it. And it comes from living on a weather report all day, right? So they're always checking a weather to inform decisions and sort of win out where they can ahead or after a given rain event. And so just being able to fit your management in is a big part of this, whether it's having wet falls and being able to get in the fields to plant your cover crops, or whether you're going to aerial seed or directly drill that seed to the workable days we talked about in the spring, that you can potentially help dry out the soil or get into the field earlier to what I just said about greater potential water infiltration in the summertime. All of these things are sort of affected by the time of the year, how much you're getting, what kind of cover crops you have in your field, the cash crop you're using. So it's a lot of factors at play and farmers are always out there making all of their decisions contingent on theses kinds of climatic dynamics.
Sarah Hill:
Okay. So how can cover crops play a role in integrated fertility management?
Steven Mirsky:
Cover crops are not a one-size-fits-all model, right? We have cereal cover crops, let's just use those, for example, they're not putting new nitrogen into the system. They will scavenge nitrogen in the fall for example, and they will retain nutrients. And the idea is that they cycle them and they return them back the following growing season so that it helps tighten up your nutrients. So people are always asking you, "Can I reduce my nitrogen? Can I have more of a lower inputs? How do I adjust my end rates based on my cover crops?"
Steven Mirsky:
The general message that I've been saying to folks based on many, many years of experience of looking at the decomposition at nutrient release of cover crops, is that don't expect much nitrogen from your cereal cover crops. You're not planting cereal cover crops to store a bunch of nutrients in the fall and give back to you in the summertime. That's just not a thing. And you're not getting that much nitrogen during the growing season from a cereal cover crop. You are slowly over time building up your soil organic matter, potentially, or at least some lay fractions of so organic matter that provides some levels of increase in the overall nitrogen that's during the growing season, albeit not a lot, but you're slowly increasing it. And that will create more buffer against nutrient deficiencies in the field.
Steven Mirsky:
Now, legumes are obviously a totally different equation. They are not only bringing a lot of new nitrogen into the system, but it's at such high levels that you can really see impact on your or fertilizer bill, right? So if you're getting good legume cover crops, you can greatly reduce your nitrogen inputs for example. And so a lot of farmers are exploring strategies for managing cover crops and how they fit legumes in their legumes are sort of the challenge in a lot of regions to get it well established and to get hyper performance, but a well managed legume cover crop can often give you easily 50 to a 100 pounds of nitrogen during the growing season. So it can be substantial.
Steven Mirsky:
So we're trying to provide sort of adaptive nitrogen recommendations to growers and that helping them get a sense of how much nitrogen they're going to get from their covers, how much nitrogen they need to additionally apply to meet the needs of the cash crop and then trying to give them eventually more spatial information, right? That's sort of the putting the precision in sustainable that if we can know that we have parts of the field that have high cover crop performance and potentially higher nitrogen, can we adjust our nitrogen rates throughout the field to reflect the benefits of the cover crop? I think that would be a great win for growers.
Sarah Hill:
Well, thanks so much, Steve. We are out of time for today. Where can our listeners go for more information about some of the research and work that you are doing?
Steven Mirsky:
Well, I strongly encourage folks interested in cover crops to go to their regional cover crop councils. Those are the one stop shop for cover crop information, the Northeast, the Southern, the Midwest, the Western, these are all regional councils that are providing extensive out materials that we're developing, decision, support tools, collectively and independently with a whole host of recommendation systems, all around species selections, seeding rates. We have tools around economics coming out. We have tools on nitrogen coming out and water management, and those regional councils are just incredible, both for going to their annual conferences and activities when those occur, as well as just going to the websites or using the materials. They really represent some of the most robust and rigorous information around cover crops and management.
Sarah Hill:
Great. Well, thank you again so much for joining us. This has been fantastic, Steve.
Steven Mirsky:
I sure appreciate it. Thank you. I wish you all well.
Michaela Paukner:
Thanks to Steven Mirsky and Sarah Hill for today’s conversation. How do you incorporate cover crops into your operation? Do you make site-specific adjustments? Let me know by emailing mpaukner@lessitermedia.com or calling 262-777-2441. If you’re looking for more podcasts about strip-till, visit striptillfarmer.com/podcasts or check out our episode library wherever you get your podcasts. Finally, many thanks to Terrasym by NewLeaf Symbiotics for helping to make this strip-till podcast series possible. From all of us here at Strip-Till Farmer, I’m Michaela Paukner. Thanks for listening.
