▶ Wisconsin Cover Crop Selector Tools and Biomass Targets

0:05
All right, you can hear me OK.

0:07
Yep.

0:07
You’re all good to go, Dane.

0:09
Great.

0:09
Thank you.

0:10
All right, well, thanks for the invitation.

0:12
I’m happy to be here.

0:13
And yeah, we’ll, we’ll get right into it.

0:15
So I think harvest season is actually a, you know, a good time to be thinking about cover crops, right.

0:19
So I’m going to spend some time today talking about cover crop tools and targets that’ll help folks think about their upcoming cover crop goals.

0:27
So we’re just gonna start with an overview of an update to the Cover Crops Selector tool from the Midwest Cover Crops Council and then we’ll discuss some research backed biomass thresholds that are good targets to aim for when using serial rye as a cover crop.

0:44
OK, so yeah, talking about the cover crop decision tool update first here.

0:49
If you’re not familiar with the Midwest Cover Crops Council, it’s a great organization, one that UW is a part of.

0:55
It’s this collaborative network of university researchers, farmers, agronomists, agency partners across 12 Midwest states that you can see here on the slide, as well as Ontario and Manitoba.

1:06
The goal of the organization is really to facilitate practical data-driven cover crop adoption as well as to help farmers who are already using cover crop, you know, make informed choices around like species selection and management.

1:19
So lots of this, you know, regional research and practical experience has been translated into several educational articles, videos, cover crop recipes.

1:28
Wisconsin has quite a few of those online, but also decision support tools like the cover crop selector tool that we’ll just look at here today.

1:37
I won’t have time to like dive in depth into the tool and how it works and how to use it and stuff.

1:41
So I’d encourage everyone to visit the link that should be in the chat there.

1:44
Spend some time with it.

1:45
Basically, in short, you, you select your county in Wisconsin, then you have the option to input like anticipated cash crop planting and harvest dates.

1:54
You can choose the primary goals you have for using the cover crop.

1:58
And then the tool basically generates like customized species recommendations and like local planting windows.

2:03
So it’s a really great sort resource if you’re, you know, kind of just starting out with covers, but I think there’s really something in there for everyone, regardless of where you are on your on your journey.

2:12
So the cover crop tool for Wisconsin here went to underwent a comprehensive update this past spring in 2026.

2:19
And this was, you know, about time it the tool had not been updated since since 2018.

2:23
So this this new update really reflects a lot of the more updated research findings as well as practical experience that’s been gained across the state since then.

2:32
So a huge thanks to all the committee members, farmers, agronomists, seed dealers, UW Madison Extension, NRCS, County conservationists, and the Midwest Cover Crops Council staff.

2:44
They all participated in this update and made it possible.

2:47
So I’ll just spend a few minutes here walking you through what is new on the tool.

2:52
So one of the big updates, and this is a little bit more behind the scenes, but it makes the tool much better involved refining seating dates based on some of the updated 30 year frost date dates from NOAA.

3:05
So using their, their new weather data.

3:07
So over the over the past, you know, several years, our frost dates are shifting right for both spring and fall.

3:12
And it varies by county quite a bit as you can imagine where you are in the state, right?

3:17
And because the frost dates are are shifting, you know, shifting earlier in the spring, later for fall, some of the optimal seeding dates for for cover crops that the tool reflects have shifted too.

3:28
So by incorporating this new weather data in the background, we’re able to generate county specific planting dates for each of the different cover crop species in the tool.

3:37
So again, big improvement to the previous version that just kind of relied on broad statewide or regional averages.

3:45
So next, what else is new goals, right?

3:48
So one advantage of the tool is that you can filter cover crop species by certain goals like reducing erosion, managing weeds, providing quality grazing opportunities.

3:57
This most recent round of updates, we added two new goals to the list, and those were early interceding and winter survivability.

4:05
And this generally reflects increased interest in these two cover crop goals from farmers and other practitioners across the state.

4:12
So this is what it looks like on the tool.

4:14
You go in and you select a goal.

4:16
You can see these two new options in the menu now.

4:19
So there’s now thirteen goals that you can filter cover crop species by.

4:23
And so this is what it looks like for I believe this is Marathon County when we, you know, want to rank cover crop species, for example, by their winter survivability.

4:32
To no surprise, your rye is ranked the highest, but you can see, you know, there’s some other cover crop options with decent overwintering potential that folks could explore.

4:40
So just one quick example of how to how to use that tool and some of the new goals that are added in there.

4:47
So each cover crop species features an associated information sheet outlining like detailed planting, termination, cultural trait information.

4:56
And they also include lists and ratings for potential advantages as well as potential disadvantages, right?

5:01
So some potential advantages might include things like soil building properties, attractiveness of beneficial insects.

5:08
And all of these were reviewed and updated in our most recent spring update alongside like the potential disadvantages too, like the potential risk of carrying a disease to the following cash crop or delayed emergence of the cover crop.

5:22
So these information sheets are kind of like a, a really comprehensive resource and a really good way to directly compare species based on your goals.

5:30
So you can easily go in and see things like, you know, what is this doing?

5:33
What is this species going to do for me?

5:35
Or, you know, on the contrast, you know, what should I be cautious about?

5:39
Where should I temper my expectations?

5:41
Several species we have like additional comments, which is what you can see here on the on the screen, like a big chunky paragraph there, but get into a little bit more nuance.

5:51
So just make sure to review those information sheets when using the tool.

5:55
It to help make some good decisions about the cover crops that you’re planning on planting.

6:01
Alright, so we also added 16 new cover crop species to the tool.

6:06
This was a a big effort and I think it supports greater flexibility, more cover crop options for diverse cropping systems.

6:13
Some of the added species are, you know, growing in popularity across the state and may offer alternatives to some traditionally used species.

6:21
For example, winter camelina, it’s a winter Hardy brassica that can overwinter in Wisconsin, possibly offering a viable alternative to cereal rye and certain crop rotations.

6:30
So yeah, just a a good amount of new species added to the list for people to explore.

6:35
When it comes to grasses, we added six new species, spring triticale, Proso millet, German Millet, sorghum, corn and black oats. Brassicas, 5 new species on there, mustard, African cabbage, collards, kale and that winter camelina that I just mentioned. 4 new species of legumes, common vetch, soybean, white clover and balansa clover.

7:02
And finally, 1 new species of broadleaf and that would be that would be flax.

7:07
So again, pretty comprehensive update to the tool.

7:10
I think there’s a lot of good information in there.

7:12
If you’ve used the tool in the past, I suggest you check it out again because it’s changed quite a bit in terms of its functionality as well as some of the species options that we have in there now for Wisconsin big old QR code there to to check it out.

7:26
I think the links will be shared in the chat as well.

7:28
And just thanks again to everybody who helped in the update.

7:30
It was really great to have, you know, input from both researchers and farmers and agronomists and the practitioners who are really using these, using these species on the ground.

7:40
And I think the tool reflects a nice balance of both research and again, practical on the ground experience.

7:44
So thanks again for everyone that helped out with that.

7:47
All right, so let’s shift gears a little bit here and focus in on on cereal rye and talk about some of those biomass thresholds.

7:54
So moving from tool to targets.

7:57
So when we talk about cover crops, I think it’s easy to focus kind of solely on on what species to plant maybe.

8:02
But effectively using cover crops really starts with the question like what, what problem am I trying to solve in this particular field?

8:09
What is my goal of using this cover crop going to be?

8:13
So that’s step one, right?

8:14
And once you identify kind of that goal, what that target outcome is, your management strategy is going to shift accordingly, right.

8:20
So I think it’s, it’s no single cover crop species or management approach can deliver every single benefit all at once.

8:28
And no matter what that goal is achieving it typically depends on how much biomass that cover crop produces before it’s terminated.

8:37
And so if biomass is so important, how much do you need, right?

8:40
That’s, that’s kind of the first question in a, a farmer’s mind.

8:44
And you know, classic Extension answer here.

8:46
It it’s going to depend on which benefit you want.

8:50
Fortunately, here in Wisconsin, we don’t have to guess at some of those biomass numbers anymore.

8:56
So researchers here at UW Madison within the our faculty extension specialists have established some clear biomass thresholds tailored specifically for Wisconsin production systems that are using cereal rye, which is our state’s most widely planted cover crop.

9:12
And these cover crop goals where we have established thresholds are reducing nitrate, leaching, erosion and run off control and weed suppression.

9:23
So we recently got together, a bunch of us and kind of sat down and and tried to synthesize these different target recommendations into a UW Extension publication, which is available free online.

9:34
It’s titled Cereal Rye Biomass Thresholds for Cover Crop Goals.

9:38
And for the rest of my time today, I’m going to just kind of run over give a high level overview of this resource and we’re going to cover how much biomass from low to high is needed to see some of the benefits that you might expect for each of these cup of crop goals.

9:52
OK, so we’re going to start with, you know, some water quality and and nutrient management considerations.

9:57
And these recommendations are coming from Dr. Matt Ruark’s nutrient cycling and agroecosystems lab.

10:03
So for some context here, we’re we’re thinking about using cereal rye with all manure applications that are, you know, going out in advance of any real cash cash crop needs, right?

10:14
It’s pretty positive to apply some of this manure to a cover crop field, right, because this cereal rye is capturing some of that excess nitrogen from the manure that may otherwise leach away in its biomass.

10:28
So what are some of the benefits and tradeoffs associated and these associated biomass thresholds for cereal rye when it comes to water quality?

10:36
These are basically the three numbers to to keep in mind here.

10:39
So we’re looking at less than 1000 lbs dry biomass per acre, 1000 to 2000 lbs, and greater than 2000 lbs.

10:48
And here’s just an overhead shot of what some of these different biomass numbers look like in these two foot square quadrats here.

10:58
OK, so let’s dig into it a little bit.

10:59
So with less than a 1000 lbs of cereal rye biomass, you’re really, you’re not really seeing any major, major reductions in nitrate lesion, right?

11:10
It’s capturing some excess nitrogen, but you’re not moving the needle too much here.

11:15
Once you get into the 1000 to 2000 lb range, that’s really the the sweet spot and where we want to be to capture some of that excess nitrogen with minimal trade-offs.

11:27
Once we’re up over the 2000 lb threshold, there are enhanced benefits to water quality through more excess nitrogen capture, right?

11:36
So, so more is better in this case, but you are kind of injecting more risks and trade-offs into the system, especially, you know, when you’re using manure and you’re potentially looking for that, that nitrogen credit to the the following cash crop.

11:51
You just start to get a lot of biomass past this point and a lot of nitrogen uptake.

11:56
And there are some examples out there, you know, and these are maybe kind of worst case scenarios, right, where without a cover crop, you might be maximizing cash crop yield with less nitrogen than you would otherwise need if you had a cover crop with say 3000 lbs of, of biomass.

12:11
So important to kind of consider some of these trade-offs, especially when it comes to nutrient management when thinking about these different biomass thresholds.

12:19
And so, you know, some of this work from from Doctor Ruark’s lab has shown that, you know, you do need to adjust that manure nitrogen credit when growing cereal rye in some cases, right?

12:28
If you’re under 1000 lbs, you don’t need to worry about making any adjustments.

12:32
You’re not really doing that much to move the needle on capturing excess N in any case.

12:36
But when we get into that 1000 to 2000 lb range, which is kind of the sweet spot where we’d want to be, sometimes you do need to consider an adjustment.

12:44
Again, the cover crops are taking up nitrogen reducing leaching, but the cereal rye is not necessarily just taking up the nitrogen from the manure that was going to leach out over the winter, right?

12:53
It’s also probably taking up some of that nitrogen from the soil that would be available to the cash crop.

12:59
So we need to think about adjusting that credit.

13:01
So, you know, Dr. Ruark’s lab suggests subtracting 35 lbs per acre from that manure credit.

13:08
So if you’re anticipating, you know, 50 lbs, back those expectations off maybe to just 15 lbs.

13:13
Going over 2000 lbs requires a more serious adjustment, right?

13:17
And this is something that we’ve, we’ve discussed more recently.

13:19
This A4178 publication here.

13:22
Matt wants to put kind of a, a, a cap on it, but you know, that adjustment is going to be looking at you’re probably in the 60 to 70 lbs of nitrogen per acre range if you’re getting up of that 2000 lb threshold.

13:35
So you know, kind of just to wrap this up, it’s, it’s positive that you don’t have to grow like multiple tons of dry matter biomass, right, to achieve some really meaningful nitrogen capture that can reduce nitrate leaching into into groundwater.

13:49
But you need to cut, you need to be mindful, right, of, of nutrient management and adjust that, that strategy, you know, especially if you’re getting above that 2000 lbs biomass for the cash crop, especially if you’re going to be expecting a manure nitrogen credit.

14:04
OK, so let’s keep moving on here.

14:06
We’ll take a look at another goal here still related to water quality.

14:10
And this is related to how cereal rye biomass can help reduce erosion and, and runoff.

14:15
So cover crops, right, can be a really powerful tool to reduce runoff, which carries away, you know, both sediment and nutrients, the big one being phosphorus, right?

14:24
And in runoff, phosphorus may be, you know, kind of tied up in soil particles or dissolved in water.

14:29
But together we think of these both, both these forms are, are referred to as total phosphorus.

14:34
And that’s what we’re going to be focusing on here for, for this piece.

14:38
So research from Dr. Francisco Arriaga’s Sustainable Soil Management Lab has shown that about 1500 lbs of dry matter per acre is a reasonable biomass target to achieve significant reduction in, in sediment and in total phosphorus losses cutting cutting those losses by 50% compared to like a no cover crop control.

15:01
So his group figured this out.

15:03
This threshold was determined kind of in, I think, a cool way.

15:06
They used a, a simulated rainfall simulator to do this.

15:09
So they simulated a 1 1/2 inch rainfall event at a rate of 3 inches per hour.

15:14
So this is a a pretty heavy rain kind of the similar the deluge patterns that we’re kind of used to seeing nowadays here in Wisconsin.

15:23
And so if you recall that the sweet spot for capturing that excess nitrogen right was between 1000 and 2000 lbs, call it 1500.

15:30
So the optimal biomass threshold for for erosion and runoff control falls within that within that range as well.

15:36
So you know, again, similar to capturing excess nitrogen, more is better.

15:41
But like this 1500 lb range is a reasonable and manageable amount of biomass that’s still going to move the needle on preventing some of that major erosion and nutrient loss from the fuel.

15:55
But you know, it’s like, it’s important to mention that while while cover crops help, they’re not like the silver bullet, right?

16:00
There’s also management practices that can be used in concert with with cereal rye or cover crops to help control some of the phosphorus losses.

16:07
You know, using soil sampling to track soil phosphorus levels and you know, drawing them down if they’re they’re greater than optimum for your specific crop rotation. And using other, other conservation practices, you know, injecting liquid manure contour strips, you know, using grass waterways. These are all things that can be used in concert with cover crops really help, you know, stem some of that phosphorus loss and further run off from the field.

16:31
So just just one tool in the tool kit.

16:34
But I think it’s really helpful to have that biomass target to aim for.

16:37
So you know, you’re going to get meaningful reductions if you hit that, if you hit that 1500 lbs.

16:43
OK, so moving on to weed suppression.

16:46
So we’re specifically looking here at some of the more difficult to manage weeds due to herbicide resistance issues.

16:52
So things like waterhemp and and giant ragweed.

16:55
And this work comes from Dr. Rodrigo Werle’s Wisc Weeds lab.

16:59
So here we’re going to take a, a big jump up in the recommended biomass thresholds from what we’ve seen say in the, in the water quality perspective.

17:07
So to focusing here on water hemp first, to achieve a, a 50% reduction in water hemp density so that, you know, fewer, fewer plants emerging, you’re going to require a really high level of biomass.

17:20
Dr.

17:20
Werle’s group has shown that 4500 lbs per acre is what’s necessary for that 50% reduction in waterhemp plants emerging.

17:28
You know, if getting to 4500 lbs is maybe too much of a challenge, deemed too risky, 2500 lbs of cereal rye biomass can actually still be helpful in moving the needle.

17:38
It can reduce waterhemp biomass by 50% or more.

17:42
So slower growth, reduced vigor.

17:44
So still waterhemp control benefits at this lower biomass threshold.

17:48
You know, smaller weeds are easier to manage and are are good from a a resistance management perspective.

17:54
So moving into giant ragweed, a little bit different here.

17:58
Dr. Werle’s group figured out that, you know, 3500 lbs of per acre of cereal rye biomass is necessary to reduce that giant ragweed biomass by 50%.

18:08
Well, you’re gonna need 4250 lbs per acre to achieve that 50% reduction in, in seedling emergence.

18:15
So you know, as you might imagine to obtain some of these these biomass levels for weed suppression, it’s going to be really important to to plant early and, and terminate late.

18:24
So, you know, this is especially an attractive option for a planting green into a, a soybean system for example.

18:32
And that’s where most of these recommendations from the Wisc Weeds group has come from.

18:36
It’s this planting green soybean system.

18:41
They are looking more into planting green into corn, but not something that we’d recommend right now.

18:47
Again, thinking a lot about potential issues in in nitrogen tie up and having that big biomass.

18:52
But for for soybean, which is where these recommendations come from, it’s a good, good weed control option.

18:58
So one thing I think it’s important to note when thinking about cereal rye for weed control strategies is that under field conditions, it’s pretty difficult to get to that 3500 lbs per acre of rye biomass early enough in the season to suppress giant rag, because that’s a weed that’s emerging pretty early in the spring.

19:17
So waterhemp, on the other hand, doesn’t really begin to emerge until, you know, mid to late May, making this cereal rye suppression of water hemp a much more viable option than giant ragweed.

19:27
And again, you know, accumulating enough of that biomass for effective suppression is going to require delaying termination until after or after planting.

19:35
OK, so just to to wrap up here, we threw a lot of biomass numbers out there, you know, dry matter biomass numbers, but how can a farmer crop consultant, you know, industry rep, somebody that’s out there in the field, just tell how much they arrived biomass they might have without clipping and weighing and drying.

19:51
It all turns out that height can be a pretty good proxy for biomass.

19:56
And UW researchers from the Wisc Weeds lab and others have assembled a lot of this multi state data to come up with some really good cereal rye heights that correspond to these different biomass thresholds here.

20:08
So that’s what you’re seeing on this slide.

20:10
You know, 1000 lbs of dry matter per acre roughly, you know, 8 inches high moving all the way up to that, that 4000 lb level, looking at about 32 inches.

20:20
And you know, if you forgot a tape measure your leg, it can be a pretty handy guide too.

20:25
So you know, again, if you’re looking for that 4000 to 4500 lb level, you’re looking at like cereal rye that’s going to be to the upper thigh.

20:33
Of course, this is going to be relative to how how tall you are, but this is a kind of a quick guide that you can use to estimate biomass when you’re in the field.

20:43
So another useful tool to estimate biomass and this was developed by again, UW researchers Damon Smith and Shawn Conley.

20:51
It’s a cereal rye biomass estimation tool.

20:53
And this is up and running as of this spring on the crop risk tool platform, part of the Crop Protection Network.

20:59
And basically what this model allows you to do is estimate what biomass you may have in the field nearing your planned termination date.

21:08
So on this example here, I, you know, planted my cereal rye on October 1st, hoping to terminate it on May 1st.

21:15
I’m in Edgerton, right on the Rock and Dane County line.

21:19
And when we run this model here for May 1st, it’s estimating that I’m going to have 3393 lbs of biomass accumulated, right?

21:28
So you’re able to gauge a little bit whether you’ve hit that biomass threshold goal.

21:31
If I’m looking for 4500 lbs of biomass, you know, I’m not quite there yet, right?

21:37
So maybe I can go in then adjust my end date, maybe bump it out and another week.

21:41
And then it’ll, that tool will allow you to, to kind of get an idea of when you might need to wait until to hit that threshold pool.

21:47
So another good way to to estimate biomass using maybe maybe from your computer chair prior to heading out to the field.

21:56
OK, So again, easy to throw some numbers out there, but it’s harder to actually manage the cover crop to, to get there.

22:02
So in this publication that I referenced earlier, there’s a lot of information on management strategies to accumulate biomass as well as a couple of useful tables.

22:11
Example of one right here that highlight termination timing trade-offs, right, that need to be considered whether you’re growing corn or soybean after the cereal rye cover crop.

22:20
Again, that cash crop is going to help guide some of your decision making.

22:23
So I’d really encourage you to, to check out that publication for more detail.

22:27
Each of these tables have like a clickable element that’ll expand and give you a lot more information and nuance.

22:33
So again, good spot to to check things out for more details.

22:36
And with that, thank you very much.

22:39
I’ll, I’ll wrap it up here and turn it over to Hannah.

22:45
Yeah, thank you, Dane.

22:46
I did have a, a just two little quick questions as we transition as well.

22:51
So one that came in is they’re like, yes, we know that cereal rye is #1 if can you tell from the cover crop tool or anyone from extension know what are the cover crops that might be #2 or #3 in the state?

23:06
Does anyone have any guesses?

23:08
Yeah, that’s a, that’s a good question.

23:10
So the, the tool, the Midwest cover crop tool will not, will not give you that information.

23:16
It’ll give you some like, you know, good cover crops that might fit into, you know, the certain system that you’re in, but it’s not going to like rank them by their, their use in, in the state, for example.

23:28
Yeah.

23:28
But I mean, that’s a, that’s a good question.

23:30
I, I think that’s a lot of our, you know, overwintering grasses are going to be, you know, common in, in popularity here just because of the, the growing season.

23:38
And typically if you’re following a corn or soybean rotation, it’s going to be a little more difficult to have like a diverse cover crop selection.

23:46
If you incorporate, you know, a small grain into your rotation, then that really starts to open up more of your options for cover cropping, say after that winter wheat harvest.

23:55
You’re able to get more diversity out there.

23:57
So hard to answer that question exactly.

23:59
Like what’s number two?

24:00
Number three, it’s really going to depend on on your system.

24:03
But I would say that those, you know, those winter hardy grasses are, are probably our our number one most popular options just given the systems that we’re that we’re in.

24:12
But yeah, definitely interested to know what other people out there are, are thinking what’s worked for you.

24:17
I think the camelina option is going to be kind of an interesting one to see where that goes out into the future again because of that overwintering potential able to fit it in some of the corn soybean rotations a little easier, especially after silage.

24:28
So anyways, sorry that didn’t really answer your question, but yeah, if you if other folks want to chime in.

24:32
True.

24:33
Yeah, like my, my mind went to make sure you connect with your, your farmer led watershed groups in your area because they’re really trying a lot of the cover crops and cover crop mixes that might work in your cropping system and in your part of the state.

24:49
We know that we have less growing degree days in Northeast Wisconsin than Dane does down by the state of state line with Illinois.

24:57
And then one additional one that came up, I’ll just like make this comment in general is they really love the image on your cover slide.

25:05
And that is you can find that in the link that was shared in the chat in that article.

25:10
And if you do want to share it, share the image.

25:15
We just say just give UW credit as well as connect with the the authors and stuff to make sure that you’re crediting that.

25:23
You can definitely share that on social media and newsletters.

25:26
Feel free to do that.

25:27
You don’t have to do the whole article, but just have it that you can refer back to that.

25:32
So just wanted to make comments about that Dane, that people liked that image.

25:36
So again, Dane, yes, share far and wide.

25:39
Yeah.

25:40
Dane’s information will be shared in the chat if you’d like to follow up with him.