0:05
All right, Thank you, Chris for the introduction and for the opportunity to be here presenting with everyone today.

0:10
I really appreciate it.

0:12
So I’m going to jump right into things, but want to give everyone just a little bit of an outline so they know what to expect as I move through the presentation today.

0:20
So I’m going to start by highlighting the current status of groundwater quality in Wisconsin, kind of frame the issue of nitrate leaching, why we care about it.

0:30
Then I’ll move into some basics about nitrate leaching and agricultural systems.

0:34
And then from there, highlights a few different research studies, starting broader, looking at the Midwest, the trends we see from nitrate leaching, and then hone into Wisconsin and share some specific data on timing and magnitude that we see here in Wisconsin.

0:49
And I’ll wrap up with some potential solutions for us moving forward.

0:55
I also want to give a shout out to colleague Kelsey Hyland, who’s an outreach specialist in the egg water quality program.

1:00
She put together a fair number of these slides from a previous presentation that we Co presented.

1:05
So I’m giving her a little shout out for credit for a lot of these slides as well.

1:11
On this slide, I’m highlighting the groundwater report that came out in 2023 from the Department of Agriculture, Trade and Consumer Protection, highlighting the status of groundwater in the state of Wisconsin.

1:24
They did a stratified sampling approach, monitored about close to 400 private wells across the state, trying to get a really good coverage of the state to see what the groundwater concentrations looked like.

1:36
For nitrate.

1:38
From this report, they found that just over 7% of private wells in the state of Wisconsin are above our safe drinking water standard.

1:46
For nitrate, which is set at 10 milligrams per liter, we have that safe drinking water standard set mostly for infants and pregnant women who are at risk for blue baby syndrome to happen if we have too high of nitrate in our water and worst case scenario that would result in infant mortality.

2:04
So that’s why our big human health concern with nitrate in our groundwater.

2:10
In this report, they also found that the areas where there was nitrate concentrations exceeding that safe drinking water standard, those are most frequently found in areas with higher percentages of cultivated land production.

2:24
So we know there’s a little bit of a human influence on our groundwater and nitrate concentrations.

2:31
I also want to pull attention to the private wells that were in the range of two to 10 milligrams per liter for two reasons.

2:38
The first being that we want to be proactive and if we know that our groundwater concentrations are starting to creep up and approach that, that 10 milligram per liter threshold, if we can do something to prevent it from reaching that, that would be the best practice that we could do.

2:53
And the second reason I highlight this is that there’s a growing body of evidence showing some other human health impacts that some lower nitrate concentrations, nothing super definitive yet, but there is growing evidence showing maybe an increased risk of thyroid disease and certain types of cancers with these other nitrate related concentrations.

3:17
And so about 1/3 of the wells they tested, we’re in that two to 10 milligrams per liter range.

3:25
And so why, why do we care so much about this in Wisconsin?

3:28
It’s estimated that 70% of Wisconsin residents rely on groundwater as their main drinking water supply.

3:34
So a lot of us are really heavily dependent on this and we don’t want to be having these human health concerns.

3:42
So with that background knowledge, I’m going to move into some nitrate leaching basics and agricultural systems.

3:51
So you hear me talk about nitrate leaching.

3:53
What exactly does that mean?

3:55
What is nitrate leaching?

3:57
For us to have nitrate leaching, we first we need two things.

4:00
We need a surplus of nitrogen in our soil and we also need drainage.

4:04
So for us to have a surplus nitrogen balance, this is going to largely be influenced by our nitrogen management.

4:11
That means there is some extra nitrogen hanging out in our soil and was able to be flushed out of the soil when we have drainage.

4:18
So we have to have the surplus nitrogen balance plus the drainage.

4:22
For us to have drainage, that’s going to be a function of precipitation, your soil texture and also time of year is going to be a big, big part of this as well.

4:33
We know if we’re talking in July, our crops are going to be using up a lot of the water.

4:38
There’s going to be a high water demand, less drainage happening versus this time of year when we don’t have a crop actively growing using that water.

4:48
So when we have that combination of surplus nitrogen and drainage, that’s when we can have nitrate leaching happening.

4:58
OK.

4:58
So getting a little bit more into what is our nitrogen balance, how do we get a surplus?

5:03
We need to understand what are the pools of nitrogen in our soil.

5:08
So first we can have nitrogen inputs and this is largely going to be your commercial fertilizer or miner applications.

5:17
But then there’s nitrogen outputs.

5:19
This is the largely going to be what are you harvesting, taking off of the crop, maybe some that some nitrogen that is released back to the atmosphere, but largely going to be your your harvest uptake of nitrogen.

5:34
And then the last pool is does the nitrogen stored within your soil.

5:37
This is going to be the hardest one for us to quantify, but we know the nitrogen changes form in our soil.

5:43
It can be mineralized or immobilized as it moves from different forms.

5:51
But all these together is will make up your nitrogen balance.

5:54
So we can keep this in mind as we think about that nitrogen surplus.

6:01
And again, for us to have a surplus of nitrogen, that means our nitrogen supplied is outweighing the nitrogen demand of our crop.

6:10
I have two studies outlined here at the bottom, but these studies found that our average nitrogen fertilizer uptake in the Midwest for corn production is around 37%, so not the most efficient crop at using nitrogen.

6:25
So this begs the question then of what happens to that remaining 63%?

6:31
There’s a few different pools of where this could go.

6:34
We could have some nitrogen that was denitrified and released as nitrogen gas.

6:40
We could have some of it that was immobilized and is now temporarily stored within our soil.

6:46
And the last spin is that it could be leached out towards groundwater as nitrate.

6:52
And so we’re going to focus in on that portion that is maybe being leached out of our system.

6:59
So now I’m going to start broader looking at the Midwest.

7:01
And as I said, we’ll continue to refine our scale and get closer and closer to home as we go.

7:09
So here I’m highlighting a study that combined a lot of different studies.

7:13
You can see 325 studies they looked at and kind of condensed all the information into 11 report looking at the the impact of different management practices on nitrate leaching.

7:28
I’m gonna pull out just a few pieces of information from this larger study, but the first one I want to highlight is the impact of vegetation type on nitrate leaching across to those many studies.

7:41
So the crop that they found have crossed all these studies have the greatest amount of nitrate leaching is potato, which is on the left side of the graph.

7:50
But I’ve also converted those are in kilograms of nitrogen per hectare per year.

7:55
I’ve also converted it in the table to pounds per acre.

7:58
So for potatoes, on average around £50 per acre of nitrate leaching is what they saw from the graph.

8:05
You can get an idea of the range of nitrate leaching they’ve seen.

8:11
So these little lines that come out of the bars that represents the range.

8:15
So there’s years where it’s close to 0 nitrate leaching, but they have years where they got close to say like 140 a 130 pounds per acre of nitrile leaching.

8:28
Then as we continue to look at this, on the low end of the spectrum, we have bioenergy crops.

8:35
Those had about £10 per acre of nitrile leaching.

8:39
But if most interest to us is probably these middle crops, corn was the second highest one they saw with around £30 per acre of nitrite leaching.

8:49
The next one might surprise you.

8:50
Alfalfa as a perennial crop, we often think of it as a really deep rooted crop that can really take up a lot of nitrogen.

8:58
And while that’s true, alfalfa is also often grown in areas where it’s had a strong history of mineral application.

9:06
Maybe it’s also getting some mineral applications throughout that it’s growing season.

9:13
But I also want to point out that there’s not a lot of data, especially in comparison to these other crops on this graph.

9:19
So there’s not a lot of information on alfalfa, some indication that it might have some nitrate leaching concerns.

9:26
We don’t have a lot of data to say a whole lot on it.

9:29
So an area that we need more information on, but one we’ll keep in mind.

9:37
Last one I’ll highlight here is soybeans.

9:39
They have an average nitrate leaching of £25 per acre.

9:45
So that gives us an idea of like where the numbers fall within the Midwest.

9:53
But I also want to point out some crop rotation and nitrate leaching.

9:57
We’re often not just growing one singular crop on our fields.

10:01
We have crop rotation that we use.

10:03
So this it’s important to take that system level approach and thought to your nitrate leaching as well.

10:13
So when we look at these crop rotations, there’s some evidence of reduced nitrate leaching for corn, soybean rotation versus a continuous corn rotation.

10:22
It’s not strong enough that they were able to determine a a statistically significant difference.

10:28
But if we look at the magnitude of things about £10 per acre or less per nitrate leaching.

10:34
But this gives us the question of what would other rotations look like?

10:37
They just looked at a few different crop rotations.

10:40
If we extended or diversified those crop rotations, what would our nitrate leaching look like then?

10:47
So some some food for thought as we continue to move through the presentation.

10:53
OK, so now I’m gonna switch gears and get into some more Wisconsin specific data getting into the timing and magnitude of nitrate leaching that we are seeing here in our state.

11:05
So in terms of timing of nitrate leaching here, I’ve got a timeline of of the year for Wisconsin and kind of maybe what are crops or fields look like especially if we don’t have weren’t able to get a cover crop in.

11:20
We have pretty bare soils for a good chunk of the year if that’s the case.

11:25
And Kevin Massarck, he had a pretty long term study going on in Arlington and from that study looking at nitrate leaching, he found that roughly 3/4 of the nitrate leaching happened within the April 1st to June 30th time frame.

11:43
And if we extend that to include January through March, that number goes up to nearly 90%.

11:50
So this is our our high risk time period for nitrate leaching And something we can keep in mind now is the harvest seasons wrapping up.

11:59
Are there things we can do to prevent nitrate leaching in this January to June time frame?

12:10
So again, majority of that nitrate leaching happens between the growing seasons.

12:17
So with that, I’m going to transition into some Wisconsin Discovery farm specific data.

12:21
We’re going to hone in on one specific site that we have a couple years of data on that I can share with you today.

12:28
This site is located in Pepin County, so western Wisconsin, fairly sandy soil.

12:35
Dairy farm is is the type of farming operation we’re looking at at this site.

12:41
Here I’m highlighting a few different aspects of their site management.

12:45
So, so far it’s been in a corn soybean rotation.

12:48
Corn has been grown for both crane and pork or silage.

12:54
Following corn silage.

12:55
They did apply a plant a cover crop in 2023 using cereal rye.

13:04
The conditions that year didn’t allow for the the greatest establishment of their cover crop.

13:09
So not the greatest biomass or height of cover at freeze up.

13:15
In terms of tillage, the farm uses reduced tillage.

13:18
They either use strip or vertical tillage.

13:20
They made a single pass in the spring of 2023 and try to maintain a high level of residue at planting.

13:27
And then lastly, just going to highlight their fertilizer applications.

13:32
Over the time period we’ve been monitoring, their nitrogen applications have all fallen in that corn silage year and you’ll notice several nitrogen applications that year.

13:43
They were really trying to spoon feed that crop, give it a little bit roughly every month, give it just a little bit more nitrogen, just keep feeding it small amounts at a time.

13:57
OK, so now I’m going to transition to getting into the data on this site, but the first thing I want to draw your attention to is that we’re going to use a year that runs from April 1st to March 31st.

14:08
The reason we do this is because the leaching that’s going to happen in the time frame from now through March 31st, we know it’s going to be associated with whatever happened with that previous crop.

14:21
So we use that time time frame of April 1st to March 31st to try to align with the crop growing season and then that season in between where we know that crop had the influence on on the leaching amounts.

14:35
So on this slide I’m showing precipitation and the blue dots are the average for that month.

14:43
The dark Gray bars is precipitation that fell as rainfall.

14:46
Lighter Gray bars is what fell as snowfall and was converted to its liquid equivalent.

14:54
So across this monitoring.

14:56
In 2023, that year was generally below average throughout our monitoring with the exception of October of 2023 that was pretty wet.

15:05
October, our third year had a very, very wet summer.

15:11
June, July, August, those were both all well above average and then we had a pretty dry fall following that summer.

15:20
We did have one additional year of data that I’m not going to share today.

15:24
Our first year of data, how the lysimeters go in, there was a lot of soil disturbance.

15:30
And so we knew that really influenced the amount of nitrate leaching.

15:33
So really messed up the soil.

15:36
So we gave it a year to settle in.

15:37
So I’m just showing years two and three of monitoring after that soil settled back in and the system got back to normal.

15:46
So now I’ll switch gears and talk about drainage.

15:51
So in 2023 here, now you’re seeing bars on this graph represent how much drainage was collected for each sampling event.

15:59
Samples are collected roughly every two weeks during the winter months.

16:03
We might go to monthly knowing that the soils are froze typically and not a lot of drainage happening.

16:11
So in 2023, most of our drainage did happen in the early spring in early crop establishment time frame.

16:17
You can see a dashed line that represents when the corn silage was planted in early May and then when it was harvested and that cover crop was planted in September and we did see some drainage post harvest in November.

16:32
But again most of it happened in that early growing season and in total that first year here we had about 5 inches of total drainage last year 2024 as a reminder, really wet summer, June, July, August, all well above average.

16:54
And so that is when we saw the greatest drainage happening was during the actual growing season with a little bit falling harvest, but majority again falling in that growing season.

17:07
And last year we had nearly double the amount of drainage, about 9 inches of drainage for the whole year.

17:16
Now getting into the amount of nitrate leaching, I’m going to show this as cumulative nitrate leaching.

17:21
So we’re adding up the nitrate that leach for each individual event over the course of the year and so on this one.

17:29
Now I have these green dashed lines on the graph and that represents when a nitrogen fertilizer application was made.

17:36
And so with this, we see a really slow gradual increase in the amount of cumulative nitrate leaching.

17:44
So overall, during that growing season, pretty low leaching happening.

17:48
Despite all those nitrogen applications happening, there wasn’t a large jump following any one of those nitrogen applications.

17:57
We did see a large leaching event that happened in November.

18:02
I want to highlight that this one, like I said, we try to sample bi weekly, but our project partner had some staff turnover during that time frame.

18:10
And so it was a longer time period between getting samples collected.

18:14
So that one represents a longer time period in time.

18:18
So it is a bigger, a bigger jump partially because there’s a a bigger gap in time, but also it does indicate that there was some extra nitrogen in that soil falling crop harvest.

18:29
We can see that jump happened after the crop was harvested, some unused nitrogen still hanging on the soil and we had a wet October.

18:38
So we had some some of the excess nitrogen flushed out.

18:42
And in terms of cumulative nitrate leaching around £50 per acre that year.

18:47
And if we think back to that Midwest study that I shared earlier, corn on average was around £30 per acre of nitrate leaching.

18:55
So we’re above that average, but still well within the range of what was seen from other, other studies in the Midwest.

19:02
So within the range, but above average.

19:06
Then last year 2024, this was soybeans.

19:09
Now again, pretty low leaching throughout the year, gradual increase that began around to July through early October, then drainage kind of plateaus as we head into the winter months.

19:24
So not much, not much really what’s happening, just a really slow gradual increase.

19:29
Our total nitrate leaching last year was around £28.00 per acre.

19:33
And thinking back to that study I shared earlier, the average is £25 per acre for soybeans.

19:38
So we’re right around the average for what was seen across the Midwest for soybeans.

19:47
So that gives an idea of timing and magnitude of losses that were seen in the Midwest and Wisconsin specifically.

19:55
But I want to wrap up with some ideas of how we can reduce the amount of nitrate leaching going forward.

20:02
The first step would be if we can reduce our surplus nitrogen balance.

20:07
And the first thing we need to do is understand our nitrogen in the 1st place.

20:10
Understand our inputs and our outputs.

20:13
How much is coming in and how much is coming out.

20:17
And once we have that, know how much is coming in and get a rough idea of how much is coming out, that’s when we can start to balance the supply and demand to reduce that surplus nitrogen.

20:28
Ways that we can do that are through nitrogen rate studies like the the nitrogen optimization pilot program, try to reduce any unused nitrogen, really understand how much our crop actually needs.

20:41
We can also think about managing low yielding areas of the field.

20:44
One of my colleagues was sharing how a younger farmer was sharing how his father used to tell him any extra nitrogen to put in that that low yielding area of the field that never does good, there’s extra nitrogen put it there.

20:57
But he said he’s come to realize that it doesn’t matter how much nitrogen he throws on it, that low yielding area of the field is going to continuously be a low yielding area of the field.

21:08
So thinking about areas that maybe maybe it’s not worth putting the extra nitrogen on, maybe it’s always going to kind of just always be a poor area of the field for maybe drainage reasons or whatnot.

21:19
So thinking about how to manage those and some other strategies we can think about is splitting our nitrogen applications up so we don’t have a large pool of nitrogen all just at risk of being leached out from a large precipitation event.

21:34
These are or extending or diversifying our crop rotation.

21:37
These are avenues that we can hopefully try to reduce that surplus nitrogen balance.

21:46
The second point then is if we do have a a surplus of nitrogen, we can also protect it using cover crops and we can plant specifically overwintering cover crops are going to provide the greatest benefit for us during that vulnerable springtime.

22:03
But this is going to be dependent on planting date.

22:05
It’s going to be dependent on your cover crop biomass to see the benefit for that nitrate leaching.

22:11
Here I’m highlighting a study out of Maryland where they looked at different planting dates, looked at the cover crop biomass and how much nitrate was leaching.

22:19
And we can see the blue bars is how much cover crop biomass they were able to achieve.

22:25
So we see the earlier the planting date, the more biomass that was able to be achieved, which makes sense.

22:33
And if there was larger, the more biomass from that cover crop, the the last nitrate that was leaching is what they saw across the study.

22:40
So the earlier we can get the cover crop in, the better in terms of biomass and the nitrate leaching benefit.

22:49
And then we can think about here in Wisconsin, how, how does that relate to us what rotations exist to achieve those cover crop planting dates?

22:57
We know we have a harsh winter and it’s hard to get a cover crop established here in Wisconsin.

23:03
But some systems that come to mind as if we had had a small grain growing on our on our fields that got harvested earlier or if we have corn silage that gets harvested earlier in September and can get a cover crop established.

23:19
And then the last recommendation here is if we can conduct local nitrate leaching research, then we can continue to fine tune our recommendations for Wisconsin for Discovery Farms.

23:29
This is an area we are currently expanding on and trying to get more data on.

23:34
This is the two years of data I shared.

23:36
We’re the first two years we have of this type of monitoring for the program.

23:41
So we’re really honing in now to test the effectiveness of different conservation practices to reduce nitrate leaching.

23:48
So we can again hopefully fine tune these recommendations for Wisconsin.

23:53
Some questions that we were looking to try to be able to answer is how much cover crop biomass do we need to have a meaningful impact on nitrate leaching?

24:02
When does nitrate leaching happen in Wisconsin under different soil types, rotations, climate conditions?

24:09
And also how does manure impact that surplus nitrogen balance and nitrate leaching dynamics?

24:17
So as I said, this is something we’re actively expanding on.

24:20
I shared the data from the one site in Pepin County in western Wisconsin.

24:24
We’ve added two sites more recently in Calumet in Rock County.

24:28
So we’re expanding our our footprints of where these are the different type of farming systems and management that they have.

24:34
So more data to come in the future, just not enough yet for us to share today.

24:41
Lindsay, there was a question that came in the chat on those lacimeters, how deep are they under the soil?

24:48
Yeah, so these are installed below just so we’re below the crop rooting zone.

24:54
So typically they’re like 3 in between 3 1/2 to 4 feet down in that soil.

25:03
And then with that, like to thank the the people that make this research possible.

25:07
Without our participating farmer project partners, this really would not be possible.

25:12
So a shout out to them and all their great work for letting us be on their farm monitoring, but that can take any questions if we have time for that.