Courier New;Cambria Math;  So we'll go ahead and get started for the rest of the scientific presentations.  And again, you know, the conference is The Science of Cover Crops.  And so what we've done for these morning presentations is really identify the topics and have a really thorough review of the things that we know and perhaps don't know about what the benefits are of cover crops in these systems.  So the next presentation is by Dr. Tom Kaspar who's a plant physiologist and a cover crop researcher with the USDA ARS Labs in Ames, Iowa, The National Laboratory For Agriculture and the Environment.  And his presentation is Cover Crops and Water Quality.  Please help me welcome Tom Kaspar.  (audience clapping)  - Thanks, Matt.  As usual with these things, I didn't do all this work that I'm going to be showing you.  Some of it comes from other people but at our lab, Keith Kohler is here who's been involved with a lot of this work and a lot of the other scientists at our lab. 

  So, in Iowa, I'm going to talk a little bit about phosphorus.  But what we know more about in Iowa is nitrate losses to water systems.  And in Iowa, the big controversy has been that the nitrate levels in the Raccoon River system and the Des Moines River system and all of our rivers, Cedar River, that all empty into either the Missouri or the Mississippi River, have been going up.  As Dr. Hatfield mentioned earlier this morning, it's been partly because of our changes in our cropping systems.  About 90 to 95% of the crop acres in Iowa are corn and soybean.  In some counties it's close to 98%.  And our nitrate levels in our rivers have been going up.  The yellow line is the maximum annual concentration.  And that's important because any time those maximum concentrations get above the red line in these water sources, or especially the Raccoon River, which supplies Des Moines, our largest city, they have to remove the nitrate.   This is from 1972 to 2002. 

 A lot of our cropping system changes took place before that.   We really started to increase our soybean acres in the 1960s.  And by the mid-70s we were pretty much up to where we are today.   This 2000, whatever it goes up to, 2008 is kind of significant because in 2000, I believe it was '10 and '11.  The nitrate concentrations went down.  And a lot of the producers in Iowa said, "Whoa."  Reducing nitrogen application which was happening was having an effect, and we were starting to see a decrease in nitrate concentrations.  But I'll show you from some of our long-term data that that was just an aberration.  And they've, since then, gone back up.  So what's been the result of that? And it's been that the city of Des Moines sued.  Well, I should say the Water Works in Des Moines have sued three Iowa counties. 

 And they picked those three Iowa counties because most of the drainage systems in those counties came out into concentrated pipes.  And so they were saying these drainage districts were point sources of nitrate in the Raccoon River.  And they were polluting the river.  And that was costing Des Moines up to, well it depends on the year, up to close to a million dollars a year to remove the nitrates for the water supply for the city of Des Moines.  And where it is right now is we don't know what's going to happen.  It's going to go to the district court next summer, or this coming summer.  And hard to say what he's going to decide.  Two law professors I heard had completely opposite opinions on what was going to happen.  So it's 50/50.  But what it has done is it's gotten everybody excited about it which is, you know, whatever side of the issue you're on, it's been a good thing because people are starting to pay attention to nitrate. 

 One of the things it did was that it caused some of our commodity groups in Iowa to say, "Oh well, we're gonna go out "and see what the nitrate concentrations are "coming out of our farmers' tile drains."  This is just from 2014 which is after the 2010 and '11 when nitrate concentrations went down.  And you can see there's a lot of points there that are well above the green line which is 10 parts per million, well above the 20 parts per million which is the red line.  There's some records up there.   We've never measured as high as above 50 parts per million.  So that's getting up there.  So there's nitrate coming out in the tile lines.  That's the bottom story.  So why is this such a difficult problem? We just need to manage nitrogen better which we're doing.  People are reducing rates.  We still apply way too much in the fall but there's more spring application. 

 So I think we're making progress there but these numbers aren't coming down, or not coming down very fast.   Well, as some of our other speakers have talked about, and Dr. Hatfield showed elephants, well, the other 10,000 pound gorilla in the room is that there's about 10,000 pounds of nitrogen in our high organic matter soils, especially in north central Iowa  that's in the form of organic matter, 10,000 pounds of nitrogen per acre.  And that nitrogen is constantly cycling.  The problem is, it's not coming out when we need it to or coming out at times of the year when we don't have corn or soybeans there to take it up.  And that's what this graph is going to show.  The red line is just kind of a scenario that's when do we get that nitrogen coming out of that soil organic matter? The green line would be when corn or soybeans would take up that nitrogen when we're planting those.  So we've got these gray areas where that's nitrate that's just laying out there and it's gonna come through if we get rainfall that's gonna flush through our soil profile.  So as some, Eileen and other speakers have pointed out, one of the ideas of cover crops is to get something growing at these other times of the year like from when the corn and soybean mature 'til freeze up and then in the early spring in March and April, to take up some of that nitrate.   So nitrate losses in tile drainage? Why are tiles a problem? Well, this is a graph from Matt Helmers that basically, they're just making or short-circuiting the water pathways through the soil.  Why is that bad? Well, because the longer the nitrate is in the soil and moving, either laterally or down through the soil to groundwater supplies, things can happen. 

 It can get tied up.  It can be nitrified.  It can be bound to soil particles.  But if it's just right away shooting through to the tile, to the surface drainage, it's gonna go right into the water supply.  So that's part of the problem.  Tiling is good.  We're farming a lot of land in north central Iowa that we couldn't farm if we didn't tile it.  But there's consequences.   So we've set up an experiment.  We first started to put the tiles in in early 2000, the area we're talking about. 

 If I can get my cursor to go, is this area here.  We have 24 plots or areas about a third of an acre.  Each one has their own tile line.  We collect the tile water that comes from each of those.  In a facility like this, this is one-third of the tiles come in here.  We measure the amount of water that's going through there, and then each time we get water through there we're taking samples for nitrate from that water.  And we started this experiment around 2000.   We had already been working with cover crops at that point for about 10 years.  So we knew how to do it.  We could pretty consistently get a cover crop established in our corn and soybean system. 

 This is going to be kind of a sciencey talk showing you a lot of data.  But I wanted to show all of these different years to show you that this is not something that just happens once in a while and to point out a couple of things.  This is a graph of the amount of water coming through the tiles which is the left axis.   And the amount of tile water coming through are these kind of purple and red bars.  The red bars are where we've had a rye cover crop every year.  The blue bars or purple bars are no cover crop in a corn and soybean.  And this is no till.  The clear bars are annual precipitation.   So one thing of note is that it's, let's see, 2007, 2008,  2000, I'm getting that wrong.  Yeah, 2008, 2009, and 2010 were the four wettest combined years on record in central Iowa. 

  2000, I think if I'm seeing it right, 2008 and 2010 were the second and third highest precipitation years that we had in central Iowa in all of the weather records.  Now the other year was 1993.   So we had a lot of water flowing through the system.   Then we followed that with drier years in 2012 and 2013.   And that showed up in the Des Moines River, the Raccoon River, and all those places.  And I'll talk about it a little bit later, but those four really wet years flushed a lot of nitrogen through the soils.  And sometimes it takes up to a year, even in our small plots for nitrate to move from across the soil and into the tile lines.  But it takes even longer for things like the Des Moines River to show these responses.  But what it did was then, that graph that I showed you with constantly rising nitrate levels in the Raccoon River took a dive in 2011 and '12 because of the previous years' water moving through the profile.  The other thing about this is that what we thought was that when we first started working with cover crops and Dr. Hatfield did some of those measurements, we thought the cover crops were gonna use a lot of water and it was gonna reduce our tile drainage and that was gonna be part of the reason that we reduced nitrate losses. 

 That didn't play out.  Over here, the average, that's just about a difference of about an inch of water annually, averaged over those 14 years.  And most of those differences are like 2015.   And the reason we had a difference there is because we had a cover crop growing in the fall when we got lots of rain after harvest, in fact, four inches of rain in December.  But we had a cover crop that was growing out there.  It wasn't growing too much then but it had used water and had more soil storage available.  We also see like Eileen said that we're using water in the spring when the cover crop's alive but then the mulching effect is preserving water or causing more water to move through the soil during the summer.  So the drainage kind of balances out between what we use in the summer when we don't want water flowing through there to preserving it in the summer where we do need the water for corn and soybeans.   These are nitrate concentrations.  Again, the blue or purple bars are the no-till corn and soybean without a rye cover crop. 

 And the red bars are with a cover crop.  And I should also point out that the even years are corn years and the odd years are soybean years.  So one of our highest nitrogen concentration losses occurred in 2003 where no nitrogen was applied.  It was a soybean year.  All of our nitrogen except for what we put on with MAP and DAP is applied at planting or after planting in our corn years.   So we're not fall applying nitrogen.  2003 we think was high because we had a really dry end of the year.  In 2002 there was probably some residual nitrogen left over.  In some of these other years like 2006, 2007, that wasn't true.  And the nitrate concentrations in the soybean years were equally high. 

  So what we're seeing is that we're getting the same kind of nitrate concentrations out in both the corn and soybean years even though we're not applying any nitrogen fertilizer during the soybean years.  So it's not just corn.  Some people, I don't know if it would be true, say that you actually lose less with continuous corn.  But I don't know that.   Now here is just some nitrate concentrations during the year.  And this is from 2014.  And the blue line is our corn/soybean rotation.  So this is an even year.  So it's the corn year.  And the green line at the bottom is the corn/soybean in the corn year with the cover crop. 

 The red line is something we started in 2011.  And it was, what would happen if we didn't apply any fertilizer? So the last nitrogen that was applied to those plots was in the fall of 2011, a little bit of nitrogen with the phosphorus.  After that, we found a source of triple phosphate.  And so we weren't applying any PNK with nitrogen attached.  And we're seeing that without any nitrogen fertilizer just because of the way this particular year set up and remembering that there's a lag time between when precipitation comes and when nitrate moves to the tile that we got a lot of nitrate out without any fertilizer applied since the fall of 2011.   The other part of this is that even with the green line, you're showing April 21st.  In a corn year, our rye cover crop would be dead by April 21st.   And the effect of the cover crop on the nitrate concentrations continues throughout the growing season.  You see it start to creep up a little bit at the end of the year.   There's, we had a stoppage in tile drainage there, the gap, and then  probably in the end of September or the first part of October, we'd be planting the next cover crop to start reducing those. 

 So there's a lag time.  We've seen over all these years that maybe for some of the nitrogen, it's as much as a year before it gets from.  We have 100-foot tile spacing.  So for it to travel that 50 feet over to the tile can take up to that long, depending on how much rainfall we get.   And lastly, these are just the loads in pounds per acre of nitrate that we get out.   There again, you see that 2011 and 2012  we didn't get much nitrate out in the tiles in those years, partly because of the flushing of nitrate from those four wet years.  And then, just because they were drier, there wasn't much tile flow.  So, the cover crop every year is reducing the amount of nitrate loss.  Over the 14 years, it comes out to about 55% reduction in the amount of nitrate lost.   If we sum that up over the 14 years, in our corn and soybean plots, we lost 488 pounds of nitrogen over the 14 years. 

 In the cover crop plots, we lost about 211.  So, I guess I said 55% reduction.  That works out to 57% reduction in nitrate.   The one point to emphasize, well, I'll show it here in this one, is that we're getting a consistent cover crop every year.  It goes up and down.  We're averaging about 1,500 pounds of shoot biomass, so that'd be roughly 14 inches tall when we're killing it, some years less, some years more.  It also depends on how good a stand you get, the number of plants per acre.  The cover crop has a concentration, nitrate concentration of about 2.5%.   So we're taking up roughly almost twice as much, a little bit less nitrogen than what the reduction is.  So the cover crop is taking up plenty of nitrogen to explain why we're getting a reduction in nitrate loss. 

  What's happening to that nitrogen that the cover crop is taking up? Well, it's going back into the soil organic matter pool.  It's eventually going to come out and we've done this now for 14 years.  If you keep planting a cover crop every year and the cover crop is generally nitrogen-limited, in other words, we've done some small areas where we've put nitrogen on the cover crop.  It grows a lot more, or if you put manure on a cover crop, it would grow a lot more than what we're seeing here.  So there's potential for more cover crop growth to take up any extra that's coming out over time.   Now these are research plots.  So does this happen on farmers' fields or other researchers'? The top three sites are other Iowa State researchers that were looking at reductions in nitrate leaching.  They got less than I did: different soils, different locations.  They don't know how to grow cover crops as well as I do.  (laughter) The Tim Smith farm, this is a farmer that put in a cover crop, and it was one of these tile monitored sites. 

 He got a 48% reduction.  The Iowa Soybean Association, the red points, and I don't know if this was from that bigger compilation but, these are some of their sites.  The red points are sites that had cover crops on them.   So they're, some of their farmers are also seeing a reduction in their tile drainage nitrate when they've had a cover crop.  So, kind of to sum this up for the nitrate is that winter cover crops can reduce nitrogen losses by taking up N and reducing nitrate concentrations in the soil and drainage water when the main crop is not there.  There is some lag between the time that they take up the nitrogen and when you see reduced water concentrations in the tile.  They have to grow to have this kind of benefit.  So in other words, if you don't get much growth, you're not going to get much effect.  And they don't seem to have a large impact on the total annual amount of drainage or how much water's coming through the tile.  But there are seasonal effects, in other words, less in spring and more in the summer. 

 And then, unlike other practices like edge-of-field buffers or wetlands or bioreactors, you're also going to get, in addition to reducing the nitrate lost in the tile, you're going to get the benefits of improved soil health with a cover crop.  So, I don't know much about phosphorus.  I'll tell you this right now, none of this is my work.  But we're going to try to summarize a few things to say what are some of the same principles that would apply to phosphorus.   Probably can't see this very well but there's a number of studies that have been done in other places.   One of the big things, and Eileen talked about it, is that cover crops are going to reduce the erosion if they're there, especially if they're alive when the erosion event occurs.  And so, you see that third column, or I guess it's the fourth column, change in total phosphorus losses in runoff, big reductions in the amount of phosphorus losses in runoff.  But that's mainly due to sediment, so phosphorus attached to soil particles.  Now those soil particles, if they get into a stream or whatever, they're eventually going to release phosphorus into the water.  So that's important too. 

 But there's been a lot of interest lately in soluble phosphorus which would be phosphorus not attached to soil particles.  And cover crops have kind of a mixed effect on that.  And I'll show you a positive and negative.   I'll show you this graph which probably doesn't make a lot of sense.  But basically, there's not been a lot of research done in North America.  I've heard from Laura that Ontario's going to start some research on cover crops and losses of soluble P.  This research was done in the Scandinavian countries.  I don't remember which one.  But basically, when you have a cover crop or any plant die, and in this case they were fall cover crops that winter killed, and then you have freeze and thaw cycles, that green material is going to release what phosphorus is in that green material, especially if you've got a runoff event on frozen soil.  So the first two columns are when they had clay soil and then they're looking at the left hand, the PO4. 

 P is soluble phosphorus.   And then the total P would be that plus what's attached to sediment.  And then the second, the third and fourth column are sandy soil.  And then the last one is the plant only.  Well, you can see when they put water through the plant only, they got a lot of soluble phosphorus out.  The high 40, 27, and I guess kilograms per hectare.  But when that water that came through the cover crops went through the soil, the amount leaching out the bottom of those columns was reduced.  So if you have soluble phosphorus that comes out of a cover crop and it goes into the soil, a lot of it is going to be recaptured by the soil.  But if it's just on the surface and it's frozen and water runs through that, that soluble phosphorus will go into a surface water supply.  The caveat to that is that you're going to have a different effect with a cover crop that winter kills than one that overwinters to the spring. 

 Because if it overwinters to the spring, it's still going to be alive.  It's going to be less susceptible to the phosphorus losses.  And when you do kill it with tillage or glyphosate, the soil would be able to take in that phosphorus leached from the cover crop.  The other part of it is like we said with erosion, we're increasing infiltration.  We're increasing the amount of water that goes into the soil.  And that's going to help with phosphorus losses in the long run too.   So, cover crops can reduce soluble P losses in tile drainage by taking up soluble P when the main crop is not there, just like they do for nitrate.  But there's not a lot of evidence on that.  But that's kind of a logical thing, the same thing we saw with nitrate.  Cover crops can reduce losses of total P in runoff because they increase infiltration and they reduce total runoff and sediment loss. 

 Lots of evidence for that.  They do a good job with that.  But they can lose soluble P from their residues after they are dead, and especially if you're on a frozen soil situation.   So, I wanted to show you one last slide.  This is one of our research fields.  And you see the clumps of cereal rye out there.  And this is a new planting method for us.  This is what happens when you have ground squirrels plant your rye.  (audience chuckling) If we can just get them to put them into rows and spread it out a little bit, I think we're really onto something.  A lot less labor with this. 

 You just put the seed at the edge of the field.  They carry it out and plant it for you.   Not very consistent though.  We have time for questions.  - [Voiceover] Thanks Tom.  (applause)