Courier New;Cambria Math;  So, please help me welcome Dr. Eileen Kladivko.  [applause]  - Thank you, Matt.  I did my PhD here in Wisconsin quite a few years ago now, so it's kind of nice to get back every now and then and see all the major things that have changed in the interim.  So I was asked today to talk about cover crops and their impact on soil health and soil erosion.  And Jerry set us up, I would say all the rest of the speakers this morning, very well.  So we'll just go into a few more details on some of those topics that he brought up.  Just a quick acknowledgment of many colleagues in the Midwest Cover Crops Council.  So this group here as well as our Indiana Conservation Cropping Systems Initiative and the corn systems and climate cap.  So these groups are all people that I have worked with over the past five to 10 years in the cover crop arena, and it's been really great. 

 So let's just review.  And Jerry touched on this already, but let's review what the rationale is for using cover crops for improvement of soil health.  And it's basically to have a living and growing plant at times of the year that we typically don't have a living and growing plant if we're in a summer annual cropping system.  And what does that do for us? Well, the plants are photosynthesizing, fixing carbon, sequestering it, feeding the soil organisms by leaking some of that carbon into the soil, recycling nutrients, protecting against erosion, and basically just making better use of the time and resources that we have available than we do in typical four-month summer annual cropping system.  If you like a picture to illustrate that, this was at the Purdue Agronomy Farm a couple of years ago just as an illustration.  Corn and soybeans were both harvested that year in early September.  So the field is brown, brown all September, October, November, brown all winter, brown in the spring, not green again until maybe early May.  In between those two plots, there was a grass strip.  Not even a planted cover crop. Just a grass strip.  Green and growing all of September, October, November, half of December, green again in March and in April. 

 Basically photosynthesizing, feeding soil organisms, recycling nutrients, and building our soil.  So, as Jerry said, we're feeding the organisms much more than what we do when we have our summer annual cropping system and it's just sitting brown for most of the year.  We also want to talk about the fact, though, that cover crops are part of a system, and you all know that.  We just need to be reminded of that periodically.  There are different potential benefits as well as challenges to individual cover crops.  And we need to adapt the cropping system to make those cover crops fit and work.  So there might be some adaptation of nutrient management.  There might be some adaptation of the way we no-till or till, how we handle manure, how we handle pests, and there's a definite learning cover.  Whether you're a researcher, an Extension person, or a farmer, there's a learning curve to growing and integrating cover crops into the system.  So, in my opinion, we don't do anybody a service by just talking about all the great things about cover crops without also helping them learn how to use them properly and how to integrate them properly. 

 And there are events, such as this, farmer Field Days, workshops, webinars, and lots of materials available on the web and, most importantly, farmers talking with other farmers about how they have made cover crops work in their system.  So what I'm going to do today briefly is talk about some of the potential benefits of cover crops, and, again, Jerry has already touched on many of these.  I'm going to give you a few examples of data on soil changes that folks have measured, and then just remind us all that the details are very site specific.  So the amount of improvement that you might get from a particular cover crop depends on where you are, which cover crop it is, what the weather has been like, and so on.  So just to remind us of that.  All right, there are many potential benefits of cover crops.  Jerry has talked about those.  Most of you are aware of those many potential benefits.  Our other speakers are going to talk about a number of those.  I'm going to talk about the four items highlighted in red there. 

 So, reducing erosion, improving soil quality or soil health, increasing soil organic matter, and conserving soil moisture.  When we are talking about soil health or soil quality, we, again, need to remember that we're talking about all three aspects of the soil: physical, chemical, and biological.  And soil organic matter really kind of is at the intersection of all of those.  Today, I'm going to talk primarily about the physical indicators of soil health as well as a little bit about biological.  And some of our other speakers will be talking about some of the chemical aspects.  So, to point out for those of you who want more information, there are a couple of really excellent reviews on cover crops and soil health.  One by Tom Kaspar, one of our speakers later this morning, and one that just came out last fall by Humberto Blanco from Nebraska in the Agronomy Journal.  So I relied on those four parts of the talk today.  First thing is erosion. Okay? The classic purpose for cover crops is to cover the soil to minimize erosion by either water or wind.  So there are a number of studies on and off over the decades that have documented this. Okay? And why do cover crops reduce erosion? What are the mechanisms? Well, protecting the soil surface by having living plants as well as the residues of those plants. 

 Even where we have no till and have not a bare soil surface, the residues that get added by the cover crops help reduce erosion.  Cover crops also anchor surface residues to at least reduce their movement off the field.  There's less detachment by raindrops and flowing water.  Infiltration rates can be increased.  There's greater surface storage, in part because of the rough surface with those living plants present, and the water velocity generally gets slowed down.  Folks have also measured reductions in wind erosion by having cover crops and having that biomass above the ground.  A couple pictures here from Tom Kaspar from his work in Ames, Iowa.  These were cover crops that were grown in the fall, and then he did some rainfall simulation studies on the following spring.  So, on the left, you can see the no cover crop highly eroded there.  In the middle, the oat cover crop, which winter killed, and then it reduced erosion. 

 And then, on the right, the cereal rye cover crop that grew again in the spring.  Still pretty small there at the time they did this but reduced erosion even further.  If we take a look at Tom's data, he's expressed this as the no cover crop is the 100% erosion.  So everything is expressed relative to the no cover crop.  So on the left, you're interill erosion where he had the oats.  The erosion was two-thirds of what it was from the bare soil.  And where the cereal rye was there is 45% of what the bare soil had.  On the right, you see that the real erosion or the concentrated flow pads were reduced even more by the cover crop.  So the oats cut that erosion in half, and the cereal rye was down at about 10% of what it was for the bare soil.  So, take away is cover crops reduce erosion. 

 We have data.  They reduce them whether they're dead or alive, but they reduce them more if they're still alive.   But I hasten to add that cover crop species does matter.  Tom's study there was illustrating two fibrous rooted crops, the oats and the cereal rye.  The daikon radish is a very interesting cover crop that people are using.  This was one of our farmer cooperator fields a couple of years ago.  And we went out in mid-March.  And if you look at the surface at that point in time, there's quite a mat of those dead radish leaves covering the soil surface.  But it's very, very short-lived, and a couple weeks later, those leaves were all basically gone.  So there were still-- It's a no-till field, so he still had some crop residue from the previous year. 

 But the point is that we do not recommend radishes alone as a cover crop for many reasons, one of which is that it leaves the surface quite friable and erodible and so we always recommend that radishes be mixed with something else, quite often with a fibrous rooted crop, like oats, but it could be with other species as well.  So again, just to remind ourselves when we talk about cover crops, there are many different types of cover crops, and we have to keep that in mind.  And, again, another picture just illustrating what we don't want on the right, which is bare corn silage ground, left all fall, winter, spring, eroding, crusting, not feeding the organisms, losing nutrients.  And, on the left, a nice lush cereal rye cover crop feeding our organisms, recycling the nutrients, and protecting our soil surface.  All right, I want to talk about some other soil physical properties other than the erosion directly.  So, soil aggregation.  Jerry mentioned that the way we build aggregates is through biology.  I totally agree.  The biology is not just the organisms, though.  It's also the biology of the roots. 

 So when we have especially fibrous rooted cover crops, how do they help build aggregates? Well, they help do it physically, first of all, by simply the roots growing and meshing the particles and pulling them together, stabilizing them that way.  But they're also exuding carbon compounds which then feed the soil organisms, and then they make the sticky glues, the polysaccharides and other compounds that glue those particles together and form those stable aggregates.  Other cover crops may be more effective at increasing permeability or porosity, especially our taprooted crops where we have some deep roots that can form root channels for subsequent crops as well as provide air and water down into the profile.  We've really already talked about the latter two on there.  This is some recent data that we have, and you can learn more about this at the poster over there during the poster session from my student Joe Rorick.  But this was a four-year study as part of that corn systems and climate project where we grew cereal rye in a corn-soybean rotation and measured the mean weight diameter on the vertical axis there in millimeters.  So the bigger the number, the better. Right? This is measuring the stability of those aggregates to disintegration by water.  So the first set of bars there in the zero to 10 centimeter depth range, we basically see that both the corn and the soybean plots where we had rye were significantly greater in aggregate stability than were the ones that did not have rye.  At our next step, at our 10 to 20 centimeters, we also see some statistical significance there of building those soil aggregates where we had cereal rye versus where we don't.  And below 20 centimeters or eight inches, after four years of the cereal rye cover crop, we don't see any change in aggregation. 

 We might say that, we might hypothesize that at a later time even there might increase.  But, as Jerry pointed out, what we're really interested in is those very surface few centimeters or few inches.  And aggregate stability in my experience with various studies almost always starts to show an improvement within a couple of years of using something like a cover crop.  Cover crops and no-till working together is even better for building soil structure.  What about roots versus shoots? We sometimes are talking with farmers and they're discouraged by the lack of top growth in their particular situation.  And, while we usually try to work at how we might get more shoot growth as well, for a lot of the things that we're interested in, root growth is really more important than the shoot growth because that's where you're building the soil biology, you're building the aggregates, and so the roots quite often are more significant.  And two inches of top growth of cereal rye may translate into 20 inches, in many cases, of root development.  You certainly still need good shoot growth for some of the purposes that we have for cover crops.  If you want erosion control, you have to have some top growth if you want to graze it, if you want to use it for mulch, but all I'm trying to remind us of is that the root growth is really much more significant in many cases than just the top growth itself.  This example from one of my graduate students a couple of years ago the day after Thanksgiving, going out and looking at some radish and annual rye grass at one of our farmer cooperators. 

 And as he pulled this daikon radish out of the ground, quite a bit of the taproot below the radish came with it.  So this is, again, just illustrating that there's much more to the radishes, in this case, than what you normally see.  Everybody's enamored with the tubers, but the taproot below that is really very significant for forming channels for further root development of your cash crop as well as water and air flow down into the soil.  Okay, cover crops and soil organic matter.  This is a question that-- We usually talk about the potential for cover crops to increase soil organic matter, or soil organic carbon, whichever way you want to express that.  We expect there to be greater or the potential to build soil organic carbon because, first of all, we're growing more than if we don't have a cover crop, right? So we have greater inputs of biomass, plant biomass, roots and shoots.  We have less erosion losses, which means it might look like we're building carbon, but we're simply not losing as much as we do if we don't have a cover crop.  That can sometimes be the case or that can be part of why we're building it.  Perhaps we might have slower decomposition of organic matter because of wetter or cooler conditions sometimes.  Studies that are looking at this typically find relatively slow increases where you look at cover versus no cover. 

 Sometimes no change.  There's many factors that affect that rate of change and also our ability to detect change that might be occurring.   And we'll look at some of those factors here.  The factors that affect the magnitude of that change, of soil organic carbon, as you have cover crops.  Or, really, the magnitude of any change, not just soil organic carbon.  Obviously, if we're growing cover crops and we're looking to see a change in the soil properties, the amount of growth matters.  If you don't have very much growth, you're not going to have a very significant change over the short term.  But it's not just growth.  It's also the species and the mix of crop types.  The plant composition, grasses, legumes, Brassicas, whether you're doing a mix, whether you're looking-- What's the relative root to shoot ratio, years of cover crop. 

 Use is also important.  Of course, the longer that you grow cover crops, the more significant impact you're probably going to have.  Soil texture and soil organic carbon.  [clearing throat] Excuse me.  Clay helps stabilize organic carbon, so soils that are higher in clay generally may be able to improve their organic carbon better than a soil that does not have as much clay, has more silt or sand.  Tillage management.  We expect carbon to build up faster where we have no till.  And, of course, climate is going to affect that.  And then the ability to detect changes, actual changes, in carbon.  Most of us do not take enough samples on a regular basis to detect small changes in carbon. 

 There's natural variability in the field, even if you are doing a good job of staying within a particular soil type.  Strict control of depth.  If you take a two-inch sample but you sometimes make it one-and-a-half inches and you sometimes make it two-and-a-half inches, that makes a big difference when you're trying to detect changes in carbon.  Variations in row position in the field.  Short-term crop history.  And most standard soil fertility labs that are set up for farmer purposes do not have the research grade techniques for organic carbon that are really needed to really track that.  So that's part of the frustration that folks have with being able to detect changes in soil organic matter.  The amount of production... this is just one illustration from our work.  On the left, cereal rye at about 700 pounds per acre top growth, and, on the right, 2500 pounds per acre after two more weeks of growth.  So that's obviously going to affect that rate at which organic matter can change. 

 Tom Kaspar and his colleagues.  This is work by Britt Moore or some of his graduate work at Iowa.  After 10 years of a cereal rye cover crop in a corn silage-soybean rotation, the soil organic matter in the top four inches was increased from 4.8% to 5.3%.  So, basically, a half a percent increase in that soil organic matter.  And increased is in quotes here simply because they did not have samples from day zero. Right? So the rye cover crop had half a percent great organic matter, but whether they both increased, both decreased, or one increased and one decreased.  They can't say for sure.  In the top five centimeters, a different fraction of the organic matter, particulate organic matter, which is sometimes used to indicate changes that occur more quickly, increased by 44% and the potentially mineralizable by 38%.  So, sometimes when people want to measure increases in soil organic matter, what we try to do is take some fraction that we think changes faster and that we can use as an indicator of how that changes with time.  And, as Tom points out, these are really hard measurements to make, in that, even for this, they took 400 cores in a fairly small area to try to document and measure those changes with time.  I pulled out some additional data from that review that I mentioned. 

 This first one here was a meta analysis that was done from 37 studies worldwide, and they estimated a gain of about 0.3 metric tons per hectare per year to a 22-centimeter depth.  When I calculated that, if I did my calculation properly, that's about a 0.01% yearly gain in soil organic carbon.  Okay? So, not very fast.  Blanco and his colleagues in a semiarid environment had a range between 0.1 and 1.0 gain of soil organic carbon when they looked at cover crops plus no till versus no till alone.  And Olson in Illinois looking at tillage differences with hairy vetch and cereal rye.  Again over a 12-year period, but calculated as a yearly gain of somewhere between 0.9 for no till and 0.1 for moldboard.  Again really emphasizing that tillage difference.  So we're talking somewhere in the 0.01 to 0.05 percent carbon per year gain.  So, not huge, but after 10 years that might be 0.5% as what Tom found, and it, you know, could be more in some conditions, could be less.  Okay, soil moisture. 

 The effects on soil moisture are also relatively complex.  Again, we have to be very particular when we say, is the soil wetter or is the soil dryer? Well, it depends on when and where.  While it's living, of course, a cover crop uses, transpires moisture.  That might drive the soil out more than a fallow field.  That might be good or bad or indifferent, depending on where you are and what you're situation is.  After termination, the cover crop residues provide more of a mulch, so they often increase infiltration and decrease evaporation and potentially leave us more water.  So they may leave some of that extra water that Jerry was talking about that, if we had another inch in some of those time frames in the summer, it would make a difference.  And so cover corp has the potential to contribute to that.  I'm just going to show you some recent data that we have from Indiana as an example.  We don't see this in all of our sites, and certainly not every study that's published shows this, but as an example of what we might think of for cover crops. 

 This was cereal rye in a corn-soybean rotation.  It was terminated in mid-April, and then a couple weeks later the corn was planted.  So this was during the growing season.  This is one week in June.  We've got volumetric water content plotted.  And the first thing I want to point out is we basically have sensors that are buried in the soil at 10 centimeters and 20 centimeters with no cover.  That's the gray line there.  And then cereal rye.  So this beginning of this graph is showing that are bare-- Well, this is no-till, but our bare, meaning no cover.  Treatment had a lower water content than where we had the cereal rye. 

 We then got a rainfall event, rewetted it, and then as the soil moisture changed with time, you can see, again, that the no cover, the gray line there, is drying out faster than where we had cover.  I'm interpreting that as greater evaporation.  You then see that we had another rainstorm event, and we increased the water content.  The orange and blue lines are both of the cereal rye at the 10- and 20-centimeter depth.  They got wetter from that rainfall event.  I'm interpreting that saying we had greater infiltration from that rainfall event where we had the cereal rye versus where we didn't.  You also see that it drops off fairly rapidly there over the course of a couple hours.  That's not evaporation there.  That's just simply the way that water moves into the soil and then moves down the soil profile as a wave.  But then you see later, a couple days later, that, again, our no cover is drying out faster than our cover crop plot. 

 So, again, I attribute that to greater evaporation.  So, dryer soil conditions, greater evaporation, less infiltration is how we would interpret these kinds of data.  Soil temperature.  If you look at the gray line again, you can clearly see that the daily maximum soil temperature is higher where we don't have a cover crop compared to where we do.  The daily minimums are a little lower.  So we basically, as we expect, the temperature fluctuation is greater where the soil is more bare than where it's not.  And, again, these are not bare fields because they're a long-term no-till, but even that cover crop residue was useful.  I should have pointed out the cover crop residue is not waist high.  It was about one megagram per hectare.  So 12-inch tall cereal rye. 

 Not excessive growth.  Okay, July soil moistures, so now we've got the whole month of July.  The main point is that you can see the gray line, which is the 10-centimeter no cover, is lower soil moisture and dries out faster than where we have cover.   Okay, some other data from Iowa, which is also showing this water content impact.  The rye cover crop increase soil water storage capacity in the top foot of the soil by about 18%.  And they calculated this as equivalent to an extra 0.75 centimeters of water every time that that upper foot got rewetted by a rainfall.  The rye cover crop did use soil water in the spring, but it was replenished most years by the time that the crop was planted.  And in most years, the cover crop provided higher water content during the summer than did the no cover crop.  Effects on cash crop rooting.  Ray Wile in Maryland and his students and postdocs have studied this for quite a while. 

 When they looked at forage radish rapeseed and cereal rye versus no cover, they looked at rooting, they looked at penetration resistance, and then they looked at the rooting of the subsequent corn crop, and, basically, the taprooted crops, the radish and the rapeseed, provided for deeper corn rooting.  The rye was next, and then the no cove was last.  So, basically, those cover crop roots providing for greater cash crop root growth.  Soil biology. Where's Matt? How am I doing on time? Two minutes? - Five. - Five minutes. Okay.   Again, as Jerry talked about, by having a cover crop, we're providing more food for the soil biology during that normally fallow period.  And by having a cover crop, we are providing a little more diversity than what we typically would have in our summer annual cropping system.  Roots can grow down in the soil profile.  This one happens to be corn roots growing in the sub-soil of a no-till field where there were a lot of nightcrawlers.  And our can maybe see behind the roots there the nightcrawler castings.  But the nightcrawlers, the cover crop roots, and the cash crop roots all tend to help each other out and form channels that somebody else then gets to use later. 

 This is just one of the soils that I've worked with in southeastern Indiana.  Just to show you, it's white, there's very little organic matter, and it's very prone to soil crusting.  And so part of a study that we did quite a while back now but is kind of recycling around is how to improve that soil.  And we looked at earthworm populations.  They're generally increased by no-till compared to chisel tillage by tiling versus untiled, if it's a poorly drained soil, and by cover crops, rotations, and manure versus the control.  And our soil physical properties also tended to be improved.  So, I'm just going to quickly show you here, this is numbers of shallow dwelling earthworms per square meter.  That particular field did not have any nightcrawlers at that time.  And we basically have higher earthworm populations in both our till chisel system and our no-till system, where we had rotations with hay crop, where we had manure, which was mostly poultry manure, and where we had a cover crop.  And we had sometimes wheat, sometimes cereal rye. 

 And this was before we really knew how to manage our cover crops very well, but the earthworms responded quite positively to that.  We also measured infiltration rate.  And so if we take a look on the left here, we've got just the continuous corn infiltration rates.  Where we had our cover crop infiltration were greater, and where we had manure they were greater still.  The two different bars there are chisel and no-till.  So, other soil biology.  That's a very active area for research right now.  There's evidence for greater biomass, greater activity of many different organisms, whether it's the micro fungi or the bacteria or the fauna, like the earthworms, soil enzyme activities are being measured, the diversity of populations.  But the methods for these measurements, plus their interpretations for practical use, are still evolving, they're really kind of in their infancy.  So there's great potential there. 

 But what the practical impacts are aren't clear yet, and we're really looking forward to learning a lot more over the next five to 10 years.  Okay, so wrapping it up then.  Potential impacts of cover crops for the Midwest, including Ontario, include that greater soil health and crop productivity, conserving our soils resource base, improving water quality, making our systems more resilient to stresses from climate.  But the magnitude of the effects is very site specific, and we have a lot more work to do in order to take full advantage of all those possibilities.  So I will end.  I will just leave this up here, the resource slide of some of the resources that are available for cover crops in the Midwest.  Thank you very much.  [applause]