University Place

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Matt

So, up next is a topic near and dear to my heart, Cover Crops as a Nutrient Source, and our presenter is Dr. Laura Van Eerd; she is an associate professor in the area of soil fertility, in cover cropping, at the University of Guelph, at the Ridgetown Campus. So please help me in welcoming Dr. Van Eerd. (applause) Thanks, Matt; I usually try to open with a joke, and I had a soil one, but I thought it was too dirty. (audience laughs) I have a corn one, but it's kind of corny, so I just won't go there. So it's really nice to follow Jeff and Eileen, because they kind of set the stage, and you might find it a bit repetitive, or you could view it as reinforcement. So a lot of what I'm saying is going to reinforce what the previous speakers have said. So the topic was Cover Crops and Nutrient Source; I'm going to focus on nitrogen, because that's my area of expertise, and I know Tom's going to speak a little bit about phosphorus. I guess with phosphorus, the question is the balance, right? What are you losing through erosion, versus what are you losing through dissolved reactive phosphorus? But in the case of nitrogen, it's complex, and I guess I'm trying to look at it from the point of view of your producers. So how are you going to determine how much nitrogen to apply to your field? We're not going to talk about when, and there's lots of issues there, and perhaps Tom can talk about losses from nitrogen,

but this is the whole goal

So how much are you going to apply? Here's my money shot, because this keeps me in business. This is the nitrogen cycle. It's complex, and that's good, but that means it's complicated. And what do you do on your farm? How much are things circling and cycling? How much are you losing in those different pathways, right? And then add on to that how much manure, crop residue, cover crops, and then your fertilizer, which is the main thing that you manage, you control on your farm. So it's complex, keeps me in business, keeps me excited about the research,

but I guess we can just pair that down to

on your farm, here's what I think the nitrogen cycle, simplified,

looks like

it's taking that organic matter; and in this case, we're talking about the nitrogen, and we're going to mineralize that,

make it into something that's plant-available

the nitrate, the ammonium. And what I want to do is, how do you maximize that on your farm. Right? And I guess it's timing; it's circling, but it's also about keeping this soil Mineral N, you want a lot of that. And Eileen just spoke about soil organic matter, soil organic carbon; you want that. But what are we really talking about? You get a soil test, and it says "percent organic matter." What that really is, is the living, the dead, and the recently dead. And the living is your crop, your corn crop, and "other," which soil microbiologists would just scream at my placing it as "other," but-

The recently dead

it's the cover crops, the residue, it's your manure, and your "other," which is your microbes, that have recently died. So that's your circle. That's what you have to manage, in my trying to simplify the nitrogen cycle.

Here's the big thing

How much corn will your soil give you, without applying nitrogen, fertilizer? Is it 100 bushels, is it 174? These are numbers we get out of our trials. The last one, 174, came from a grower strip trial, where he had red clover and pig manure in the rotation. Now if you know your soil's giving you 174 bushels of corn, without added nitrogen fertilizer, that's a good piece of information to know. That's going to help you manage your nitrogen, If you can see how much your soil is giving you. And that comes from the organic matter. It comes strictly from the circles here, releasing nitrogen. So the question at hand, because we're talking about cover crops, it's legume cover crops. How much nitrogen credit, or fertilizer replacement value, can we get from our legume cover crops? And then Tom's going to talk about losses. I'm not going to talk hardly ever. But the real thing that's missing from this picture is the "other." If I tried to do it to scale, the "other" is the main driver and Dr. Hatfield talked very well about the soil biology. That's the driver. Eileen as well;

the soil biology

the "other" that I just put into a little circle. But I'm not the only one, right? And you can look at- (laughs) but let's keep on going. So we're going to talk about red clover. It's just red clover, right? But I think it's your best bang for your buck. You need a legume to get a nitrogen credit. So the first thing to point out is that these bars, and you don't really need to know the size- well, you need to know the size of the bars. So the bars are nitrate; soil nitrate levels. And then we're going to go across time, and we're going to start in the fall, so this is the "no cover." We can see in the Fall, well, nitrate levels can be quite high. So this is in a system after wheat, and we've got wheat inter-sown with red clover, and we have Fall Control, and then it's red clover Spring Control, after wheat, we planted radish, or perennial rye grass, or oats. And we can see red clover does a really good job lowering soil Mineral N, and that's probably one of the myths out there in what we see in Ontario in the agriculture, don't use a legume if you want a lower soil nitrate in the Fall. Well actually, there's lots of data that shows planting red clover and other legumes do a really good job at lowering soil Mineral N. The other ones, yeah, they do a pretty good job, but they're a little bit behind. Mainly they're behind because you've planted them after wheat harvest, where red clover was interceded, so it's been growing the whole time. Okay, so that's the Fall. In the Spring, nitrate levels are low, whether you had a cover crop or not, they were higher in the no-cover, relatively speaking. But the main difference that you can clearly see

is right here at this time

June and July, what's going on with your corn crop? What do you hope is going on with your corn crop? You're hoping it's jumping. You're hoping it's growing quick. That's when your corn crop needs your nitrogen. That's when the red clover is providing it. That's why you get a nitrogen credit with red clover, with a legume cover crop. And I would even specify it more, a legume cover crop that over-winters. So really, it's about the timing of nitrogen release, and it's timed with the corn uptake. The other ones, yes they release it, but it's not timed well enough to give you a nitrogen credit. Okay, so that's one component of our cycle. Now, I want this bubble up here- what is the value? What can you lower your nitrogen? What's the nitrogen credit, or we could say the most economical rate of nitrogen, or they say the fertilizer value, of red clover? So let's first look at this line. Matt's talked, I'm sure, to many of you in the room about this response curve. So we've got nitrogen rates, so we've applied five different rates, and we've got corn yields here, and there's our data. Look at how nice that data fits onto the line. (audience laughs) And where the curve flattens is where you get the maximum yield, right, and if you applied more nitrogen, it didn't give you more yield, because at some point it's going to flatten, and whatever that value is, I don't know, but I just made a graph and put a line there. Okay. So the question is, what's the economical rate of nitrogen? Does it pay more to put a little bit more nitrogen? So would you have been better off just to put on, what is that, maybe 30 or 40 pounds less? You didn't get much corn anyway. So instead of, I would argue, looking for maximum yield, you want to look for the maximum economic yield. And that's okay, cause I've drawn these graphs, and that's easy enough for me to show you.

So one last thing

so we've got the maximum economic yield. What's that curve going to look like if we had planted a cover crop? Did the same nitrogen rates- are they going to bump up? Is it going to change the curve? Well, we can see, this is without a legume; maybe. Maybe we get a slight yield boost; maybe it's the same, I don't know. But with the legume cover crop, what we tend to see is that the curve peaks earlier. So we get the maximum, it flatlines earlier, and the nitrogen credit, or the most economical rate, or the fertilizer replacement value, is the difference between with a cover crop and without a cover crop. So, because this curve maxes out quicker, that's where you've got the maximum economic yield, and that difference between these two maxes is your fertilizer credit, your nitrogen credit, how much your cover crop gave you. So what we've done, and what Bill Deen has done in Ontario, is went to 26 or 28 different field sites, and farmer fields, and he ran these rate response curves. He did it with red clover and without red clover, got the curve, and now he's looking at the economical rate of nitrogen. So it depends on the corn yield, right? It depends on the cost of corn, and the cost of nitrogen. And so we can use different scenarios, these are probably pretty stable, 150 or one-to-one almost, or 100- anyway, these ratios- the point is, you know what happens when corn prices go up. Your nitrogen prices go up. So these ratios are pretty consistent, right? Regardless, let's look at the data. So we've got the no cover crop, and we did the red clover, so the maximum economic rate, how much nitrogen you should have applied was 140, 129, versus with red clover we lowered that nitrogen, the amount that you needed to be economical. And what that amounts to is about 73 pounds of nitrogen per acre in a conventional field system. Now we've got the most economical yield, and we see in all of those cases, we're getting a slight yield boost, so that's what they've called the Rotation Effect, and that slight yield boost, if we average it, it's around 5%, that slight yield boost from red clover. So not only have you lowered your fertilizer, you've bumped your corn yield, just from having red clover in your rotation. And that profits- maybe I should just keep the numbers in hectare, cause they're bigger, (audience laughs) but per acre, $28 to $48 per acre is what the profits work out. Slight yield boost, less nitrogen, pays per seed. Okay, so that's conventional till; no till, the credit in Ontario when they did this study was 60 pounds. It didn't turn out statistically, the other parameters, but for a profit, was more of a wash; numerically higher, but not a lot of statistical difference. So what else are people seeing? So nice study, kind of a meta-analysis, and they're seeing an 80 to 155, 144, those lower numbers are the second year, so this is the fertilizer credit, or the fertilizer replacement value, so quite high numbers they found. And so the data out of this publication says 69 to 138. And I forgot to mention that Wisconsin is down here, and Ontario up here, part of the northeastern states, which was news to me, but- Hairy Vetch, so that's a legume, it over-winters, and the numbers from the literature say 40 to 133. Great, so Laura, you showed me a bunch of numbers, and you're saying, "Well, what about my farm?" or "what about my cooperator's farm?" Because that is a very wide range. And what are you going to do on your farm? Because it's well enough for me to draw graphs or show you data, but that's after the fact. That's after we've done the experiment, and we've got moisture or we didn't get moisture. So what can you do? So I want to focus on this part, and how I think you can manage nitrogen, maximize it, and it goes back to our first two speakers; it's soil health. And then all these other things that complicate everything, which, it's complicated, but I think your main goal should be improving your organic matter, and cover crops play a part of that. So I want to show you our long-term trial at Ridgetown campus, that's something that David Hooker, a prof, and agronomist, has at Ridgetown, so you can see where we're located, I don't need to point out the stars, but at Ridgetown, we've got a clay loam, and it's a long term crop rotation, so they've got no-till, and conventional till. Conventional till is plough, Spring cultivation.

The rotation

so the rotation is continuous corn, continuous soybeans; corn, soybeans. That's what you guys are used to seeing in your long-term trials. What we have in Ridgetown, which I think makes it very special, and I'm biased but so be it, I've acknowledged it, soybeans with winter wheat, right; we have that rotation. And then we have corn, soybean, wheat. So now we can show you what is the value of winter wheat in the rotation? And with those corn and wheat, we have four nitrogen rate, so now we can do the response curves. And we've had these rotations over 20 years, each crop is there in each year. Just want to point out that in 2008, David Hooker increased the nitrogen rates, he added a split with red clover, so we can see some of that red clover effect. So it's relatively new red clover though, it hasn't been in the rotation for 20 years, it's only been since 2008; and in 2008, they switched to zone tillage, so it's a maybe eight inch strip where the corn goes in. So, what can we find with this data? Wheat. So many times we say oh well, with wheat, if you've got red clover you need to increase the nitrogen, our data isn't showing this. You don't need to increase your nitrogen fertilizer with red clover in the rotation. So we've got nice similar response curves, maybe not, maybe statistically we could pull out some difference, but let's not talk about that. The key, though, is you get higher soybean yields with wheat in the rotation. And you guys can't tell that, because you don't- how can you do a side by side comparison? It's only because we have this trial that we have the side by side comparisons, that we can say that all of these bars have wheat in the rotation, compared to; sorry, that's maize. I guess in scientific publications, maize sounds more scientific than corn. So maize and soybeans versus soybeans and soybeans, but anytime we add wheat into the rotation, we have higher soybean yields, and this is the average of four years, 10 to 13, quite variable years, as well. We're not seeing a yield boost to soybeans from red clover. I mean red clover, soybeans, of course, right? They're both legumes, no problem there. What we are seeing, though, is the red clover effect and the wheat effect. So the red arrow's red clover, the blue arrow is wheat, and then soybean and corn. So we are lowering the fertilizer requirements for corn with red clover; and that has only been since 2008. It's not so much that it's increasing, bumping yields, in this trial, but it is lowering our fertilizer requirements, and I don't know where that yellow- we don't have high enough rates to see corn on corn, how much nitrogen you would need corn on corn. So that's in the ploughed system, the no-till system I'll show you last cause it's not as exciting, but similar trends need less fertilizer with wheat in the rotation, and wheat with red clover, maybe it's a little bit similar, but less fertilizer with wheat in the rotation, corn... So we are improving nitrogen use efficiency with wheat, and we expect to see more improvements with red clover. And 17 to 21% increase in nitrogen use efficiency, in that MERN, in wheat, and even more with red clover. And the crop is showing it to you, right? The crop is seeing it, and what is it seeing? It's seeing the soil. So we can see it's in August, so the wheat's been harvested, you can see the red clover, but the ones where the low nitrogen rates light up, that's the ploughed system, where the corn doesn't show up as nice, right? So this treatment right here, I don't know if you can see it; yes you can. So this one is wheat in the rotation, with and without red clover; you can't see a lot of difference. But the ones without wheat in the rotation, they light up like a Christmas tree. And that is the corn responding to the soil. And what's it responding to? Soil health. Soil organic carbon. So we did the Cornell soil health test for Holland, with others, and we can see higher soil health, with the wheat, and almost statistically higher but not quite; but with wheat in the rotation, here's our fence row, our bluegrass, and conventional versus no-till. We've also published about soil organic carbon, and we can see that increases with wheat in the rotation, and we've applied for funding to look at the red clover. Is my timer right, Matt? So there's our carbon data; we can show yield resiliency. Anyway, I will stop there, and that was my last slide pulling everything together. (applause) Thank you very much. (applause)