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[00:00:07] The Dirt PodKast:
Welcome to The Dirt, an eKonomics podcast bringing you the down and dirty agronomic science behind growing better crops and bigger returns. Backed by nutrien-eKonomics.com, we break down the latest research, news, and insights to help farmers make better business decisions. Let’s dig in.
[00:00:32] Lyle Cowell:
Welcome back to The Dirt, everyone. Really appreciate you joining us. I’m your host this week, Lyle Cowell, and I’m the senior agronomist for Nutrien here in Canada. We have a big topic to dig into. We all know that soil is complicated. We know that the nitrogen cycle is very complicated, and perhaps the most complicated part of the end cycle is denitrification. It’s a big word. We hear lots about it, and here today to help us understand it a bit better is Erin Daly. Erin, you bring a wealth of knowledge and experience in the topic of denitrification. Just to roll us into the podcast here today, could you introduce yourself, let us know who you are and how you got here?
[00:01:11] Erin Daly:
Thanks for having me on. As Lyle mentioned, my name is Erin Daly. I have my PhD in soil science from the University of Alberta, and there I focused on nitrogen loss pathways, specifically N2O production. Worked in soil research for the past 10 years or so, working between industry, a little bit of policy work, and then finding my way back to academia where I work now for the University of Guelph as a project manager for a national research project called CanN2ONet.
[00:01:43] Lyle Cowell:
CanN2ONet. We’re going to come back to that in a minute. It obviously sounds like CanN2ONet is about N2O and denitrification, but let’s lead into that. Erin, can you just give the audience a bit of a definition of what is denitrification?
[00:01:57] Erin Daly:
Oh, I love to talk about this topic. It’s really fascinating. Denitrification is essentially a process that soil microbes use to breathe when there’s no oxygen available. They’re using nitrate, which is a form of nitrogen in the soil, essentially to breathe, and then they breathe out different gaseous nitrogen forms. That includes nitrous oxide, but it’s not limited to nitrous oxide. Denitrification is essentially you and I breathe in oxygen and we breathe out carbon dioxide, but microbes don’t have the ability in soil to get up and walk away when there’s not enough oxygen for them to keep breathing. When that happens, when oxygen conditions are low in the soil, they need to switch to breathing something else, and what they can switch to is breathing nitrogen.
[00:02:48] Lyle Cowell:
Great. Nitrate, a source of oxygen, but when nitrate doesn’t have oxygen, it becomes a gas, and nitrous oxide, one of those. What other gases are lost in this process?
[00:02:58] Erin Daly:
There are multiple steps to it, if you will, very broadly. We see emissions of nitrous oxide. They breathe out nitrous oxide. They’re also breathing out di-nitrogen, nitric oxide, so all these different forms of gaseous nitrogen, but nitrous oxide and N2 are probably the main two that we’re looking at.
[00:03:18] Lyle Cowell:
If we’re thinking about fertilizer, nitrogen fertilizer, ultimately about how much is generally lost by the process of denitrification?
[00:03:27] Erin Daly:
That’s a really good question, because we talk a lot about N2O losses, and we care about N2O losses because they’re that really potent greenhouse gas. That’s a lot of why the focus is on N2O. When I say potent greenhouse gas, I mean N2O is almost 300 times more effective at warming than the same amount of carbon dioxide. So we focus on N2O, but in reality, with the denitrification process, only about 1% of the fertilizer that’s being applied is being lost is N2O. It’s not a huge loss pathway. So very validly people can be like, “Why should I care too much about N2O beyond the greenhouse gas aspect?”
[00:04:08] Erin Daly:
Well, what the missing part of that equation is that, as I mentioned, denitrification also releases N2. N2 losses can be 10 times greater than nitrous oxide losses, so represent a much greater loss of nitrogen, but it’s really, really difficult to measure N2. We can do it in closed conditions, in the laboratory, but in the field, it can be really difficult because the atmosphere that we breathe is 78% N2 or dinitrogen. Instrumentation would have to be so incredibly sensitive to pick up a signal in the release of N2 from soil, so it’s really difficult. We measure N2O and it tells us that this process is happening and these nitrogen losses are occurring, and they represent a smaller fraction, for sure. We care about them because they’re that greenhouse gas. N2 is also being released and it’s a much bigger loss.
[00:05:00] Lyle Cowell:
Denitrification, when we think of the four Rs of fertilizer, it’s important to the economy of the farm because, well, we don’t want to lose nitrogen from the farm that the farmer has paid for or maybe part of the soil organic matter, mineral nitrogen, but it’s also important in terms of four Rs to the aspects of the environment and society. It’s a big important topic that we all need to understand. When we think about N2O emissions, nitrous oxide emissions, what conditions are most likely to be lost from the soil?
[00:05:28] Erin Daly:
When we’re talking about denitrification specifically, there’s a few other processes that form N2O. They’re not quite as significant, but when we’re talking about denitrification, generally it’s a mix of factors. When you’re most likely going to see denitrification losses is when oxygen levels are low in the soil. As I mentioned, that’s what causes microbes to switch from using oxygen to using nitrogen. That nitrate has to be available for microbes and so does carbon, because microbes are also using carbon for energy to actually power this process as well.
[00:05:59] Erin Daly:
We see the greatest denitrification losses of nitrogen from the system when soils are wet, waterlogged, and oftentimes it’s when plants aren’t uptaking a lot of that nitrogen as well. I’m located in Alberta. Lyle, you’re in Saskatchewan. In this part of the world, we have spring thaw. Plants generally aren’t growing. There’s not a lot of full seeded crops in Western Canada, and there is this flush of moisture. Microbial processes are generally still occurring, albeit at a slower pace, over the winter, even in really, really frozen soils. There’s nitrogen availability, there’s a flush of moisture, and crops aren’t actively uptaking nutrients at this time. That’s when we see these major spikes of N2O emissions and nitrogen loss. That’s one example. There are other areas like when we apply fertilizer and maybe the crop isn’t uptaking it right at that time, but spring thaw is a really good example of all of those factors sort of coming together to result in nitrogen losses.
[00:07:00] Lyle Cowell:
In spring, I always think of denitrification requiring wet soil, but warm soil, but we always see this puff of denitrification peak in the spring. Is that because, well, maybe the soil’s actually warmer than we think with that direct sunlight against our soil? Or is it building up and suddenly releasing from our frozen soil? Do we know why that is?
[00:07:20] Erin Daly:
So there was questions, is the N2O sort of trapped in there or is it being formed right as that soil thaws, and really, as that soil warms and we see that flush of moisture, because microbes, especially in areas that experience freezing, they’re adapted to keep on keeping on even when it’s really cold. When we say warm, it’s all relative, right? So those microbes get a little bit of warmth, that moisture from snow melt to liquid water, and also we see huge turnover of carbon at that time because of those freezing dynamics. When we say warm, it’s all relative, right? A little bit of warmth in this part of the world, spring thaw. We see those microbes are capable of waking up and producing that N2O right away.
[00:08:04] Lyle Cowell:
Reminds me of the saying, there’s no bad weather, they’re just bad clothing.
[00:08:08] Erin Daly:
Yeah, exactly.
[00:08:08] Lyle Cowell:
We’re adaptable in Western Canada as people and soy the microbes. This year you’re in Edmonton, and I think it’s been a little wet in Edmonton, as has been in other places of Western Canada. Quite abnormal for Western Canada to be quite wet, really, from one side to the other. Probable that there is more denitrification occurring this summer than usual?
[00:08:28] Erin Daly:
I would say it all depends on the availability of nitrogen. Yes, the conditions in terms of moisture are right for nitrogen losses, and we also might be seeing more losses through leaching pathways as well, because we are getting so much more water than we are used to receiving. Generally in Western Canada, we see evapotranspiration exceeds precipitation. We have a semi-arid climate. This year, that is not the case. We have lots and lots of moisture running through the soil profile. Absolutely, there is a possibility higher denitrification losses. Granted, those losses are dependent on nitrogen availability. If you have a crop that’s uptaking it, if you’ve seen those losses earlier in the season generally tend to decrease as the season continues, but also leaching losses are likely going to be an issue this year as well.
[00:09:17] Lyle Cowell:
Right. We’ve had a bit of an introduction to nitrous oxide emissions. Very important topic. Let’s turn to talk a little bit about CanN20Net. Can you describe what CanN20Net is all about?
[00:09:29] Erin Daly:
CanN20Net is a national research network across Canada. We have partners with universities, polytechnics, colleges across Canada, as well as value chain organizations and industry, like Nutrien, and the goal for CanN20Net is to investigate best management practices that are regionally tailored for different regions in Canada, because something that works in Ontario is not necessarily going to work in Alberta in terms of nutrient management.
[00:10:00] Erin Daly:
We are looking to better understand loss pathways of nitrogen from the agricultural soils and implement or tailor best management practices for those different regions, and another really cool aspect of CanN20Net that’s really important is that currently when we’re accounting for N2O emissions at the federal level, we don’t actually account for best management practices beyond rate reductions.
[00:10:26] Erin Daly:
CanN20Net kind of came about as a response to the target announced by the federal government in 2022, I believe it was, to reduce fertilizer-related emissions by 30% below 2020 levels by 2030, and what this really highlighted after it was announced was that we need more information and producers are already doing a lot of these practices on farm and we’re not accounting for them. CanN20Net was built not only to tailor additional best management practices or really zone in on what’s best for each region, because they’re highly regional, but also account for those practices in our federal accounting methods, beyond rate, but also different sources, different application times, different application places. I’m going through my four Rs here, understanding how all these best management practices and accounting for them as well.
[00:11:18] Lyle Cowell:
So how do you measure emissions? How is that done within CanN20Net?
[00:11:23] Erin Daly:
Within CanN20Net, we’re using a really, really cool innovative measurement technique that was actually pioneered by our project lead, Dr. Wagner-Riddle, out of the University of Guelph. The flux gradient method. Very broadly, because I am also not a micrometeorologist, we are measuring N2O emissions by having what we call field towers in fields that measure the concentrations of N2O in the air above a field, and so we’ve divided fields into four quadrants and we’re testing different practices in each of those four quadrants. Say, in one quadrant, it’s business as usual. In one quadrant, we’re looking at inhibitors. In one quadrant, we’re looking at the effect of variable rate technology, and then maybe in another, how we can use both of those. There’s a tower in each of these fields that’s measuring the concentration of N2O in air. So we can say this practice had higher emissions versus this one with lower emissions, and also the pattern of when we typically see those emissions so we can better tailor those practices to meet that mitigation need.
[00:12:24] Lyle Cowell:
With the towers, I believe that previous work has always been a chamber set in the soil. With the towers, did that give us a bit better understanding of the landscape loss versus just that one spot in the field?
[00:12:37] Erin Daly:
That’s a really good question, because I think there is a place for both methods. I love a chamber method. I did them all through grad school, hours and hours. Chambers are really good at comparing lots of treatments, because you can’t have hundreds of towers. It’s just not feasible. Towers are really awesome at integrating over large spatial scales and getting a really continuous measurement data set. That’s really important for N2O, because N2O happens in what we call hotspots and hot moments. It’s notoriously difficult to measure, because all of these different factors need to occur in one place in the soil for that N2O emission burst to happen.
[00:13:16] Erin Daly:
We might see 70% of our annual N2O emissions from an event that lasts one to two days. If you miss that event, you can be really vastly underestimating your N2O emissions. Chambers are really good at continuous measurements that actually integrate that concentration over a whole field. Whereas chambers can be used to test some preliminary practices and see, “This one shows promise, this one shows promise,” we’re testing multiple things. A tower’s awesome to actually implement that in the field under real conditions, agricultural conditions. We choose the most promising ones, and then we get a really complete data set so that we can understand those dynamics a little bit better.
[00:13:55] Lyle Cowell:
That’s really cool, and just two days ago, I was in Yorkton. Can you tell me about the Yorkton High Tower? And that’s not a basketball player.
[00:14:03] Erin Daly:
Lots of tower talk. The important thing is to differentiate between the tall tower and our Yorkton regional tower. So we have the field towers. They’re measuring field level emissions from practices applied to one field. The regional tower is a super cool first of its kind in Canada, CanN20Net initiative, where we have put an intake hundreds of kilometers up in the air on a CBC broadcast tower in Yorkton, and what this does is it’s measuring regional emissions.
[00:14:31] Erin Daly:
We’re getting a really large footprint of N2O concentration, hundreds of kilometers footprint over a major agricultural region in Canada. We have our field towers. We use that really excellent continuous data to improve models, process-based models that we can then take… We’ve measured at one field. We can use that data to improve our models to sort of scale up regional estimates.
[00:14:57] Erin Daly:
We’re using these models to scale up regional estimates. That Yorkton Tower then provides what we call a top-down estimate. We know those concentrations, but provides a check that what we’re modeling is actually representing what’s really happening. It’s very, very cool. I know that’s pretty nerdy, but we have these small towers, using that to feed into our models, and then our models will develop these regional estimates, and we have this really one-of-a-kind tall tower in Canada to provide a check on our modeled estimates.
[00:15:27] Lyle Cowell:
I’ve got a bit of a difficult question, but we have listeners in the dirt that are not in Western Canada. They may not be in Canada. They may not be in North America. Can you give us a little perspective of expected losses in our Canadian climate versus a bit of a global perspective?
[00:15:44] Erin Daly:
That is a really difficult question to answer, and I’ll say it’s because N2O-
[00:15:49] Lyle Cowell:
Sorry to ask it.
[00:15:50] Erin Daly:
That’s good, though. It’s good, because I think this is the challenge of N2O. We can absolutely… Or I guess nitrogen losses in general, I should say, not just focusing on N2O. This is the challenge with nitrogen losses, is that they’re affected by so many different factors. We’re talking about climate and soil type as well as management. We can control management. We can’t really control climate or soil. It’s very, very hard to compare, say, Canadian emissions to US emissions to, say, Italian emissions, if you will. It’s very difficult, because all of these places have different soils and climates, so it’s not actually providing a real fair comparison, because even within Canada, we have thousands of kilometers of agricultural land, and producers in an area that have inherently higher emissions can be applying excellent 4 R management, mitigating their losses as much as possible, but we still see higher losses because of those climate impacts.
[00:16:48] Erin Daly:
If we’re using a very default IPCC factor, we say that we’re losing about 1% of nitrogen as N2O for all of the nitrogen that you’ve applied. However, different countries have different methodologies for their inventories. Again, it’s like comparing apples to oranges. It’s really difficult. For the Canadian picture, I’ll say we’ve increased nitrogen fertilizer use, and with that, N20 emissions almost by I think 90% since the early 2000s, but we’ve also implemented a lot of beneficial management practices.
[00:17:21] Erin Daly:
The issue is that we’ve also seen an increased emissions intensity, and this is something that I think is a really valuable metric, because emissions intensity tells us how many emissions we’re having per unit of output. It’s a really valuable metric, if you will, if we’re wanting to improve our efficiency, get the most out of our nitrogen fertilizer. We’re not just looking at the amount of emissions, we’re looking at how much productivity and profitability we’re actually getting for those emissions, and that’s increasing in Canada as well. So there’s really a lot of opportunity regardless of your climate or soil types to improve our efficiency, and that will differ from place to place to place.
[00:17:58] Erin Daly:
I kind of danced around the answer, because it’s a really difficult question to answer.
[00:18:02] Lyle Cowell:
That’s very fair, but let’s bring this back, then, from the global perspective to the farmer. The farmer does not want to lose nitrogen fertilizer, and it doesn’t matter what form. What are the best practices when we think of best nitrogen fertilizer practices under the 4 R umbrella? What can the farmers do to reduce their emissions?
[00:18:21] Erin Daly:
Lyle, I’m going to drive you crazy, because I’m going to give you another “it depends” answer.
[00:18:25] Lyle Cowell:
That’s how agronomy… That’s how it is.
[00:18:28] Erin Daly:
There’s no one size fits all, and this is the challenge that we’re addressing with CanN20Net and why it’s so critical to have a national network, is that these practices need to be regionally tailored. What I would say for producers looking to maximize their nitrogen use efficiency and minimize their nitrogen losses, because that goes hand in hand. N2O, we care about because it’s a greenhouse gas, but it’s a symptom of a nitrogen loss in your system, and we care about all nitrogen losses because we want fertilizer to be transformed into crop products. We don’t want it lost through different processes.
[00:19:00] Erin Daly:
I would say the most important thing that a producer can do is work with a local agronomist to develop a 4 R plan for their soils, their climate, and their crop rotation even. Looking at the right source, right rate, right time, right place, and I even ascribe to the fact that there’s a fifth R and that’s right rotation.
[00:19:20] Erin Daly:
I would say there’s no one-size-fits-all. I can’t say, “Oh, you should do this or you should do that,” because it’s so dependent on all of these different factors, but I think a 4 R plan in place is a really beneficial way that’s been proven to reduce your nitrogen losses.
[00:19:36] Lyle Cowell:
That’s a really great point. Even when we look at the Canadian landscape and 4 R practices, the 4 R practices recognize regional differences between more wet humid areas, which, we’re all wet and humid this year, but they’re generally more wet and humid areas of Eastern Canada versus our dryland agriculture, Western Canada. Those 4 R practices, it’s such a nice way to frame better practices, including denitrification losses.
[00:20:03] Lyle Cowell:
We talk about the leaky nitrogen cycle, and nitrates aren’t just lost by denitrification. You alluded to leaching earlier on. Am I wrong that if a farmer adopts a practice that reduces denitrification, probably that practice would reduce leaching?
[00:20:19] Erin Daly:
You’re asking me all these “it depends” questions, and this is where research networks like CanN20Net come in and they’re so critical, because we don’t know all the answers. Absolutely, I am a proponent of likely if you are working to minimize nitrogen losses on your farm, that these practices are ideally going to be mitigating multiple nitrogen loss pathways, targeting getting that nutrient where the crop can access it at the right time when they need it. If you are mitigating nitrous oxide because potentially you are avoiding that loss pathway, absolutely, you might be mitigating your nitrogen leaching as well.
[00:20:58] Erin Daly:
Something that I find really interesting is what we call pollution swapping, this needs more research, is if we are really focusing on one aspect of nitrogen loss, are we missing this other aspect of nitrogen loss? This is where we need to look at the entirety of the nitrogen cycle, the importance of nitrogen use efficiency, and not just focus on one nitrogen loss pathway.
[00:21:19] Lyle Cowell:
That’s a great message. We’re coming to the end of our time in the podcast, Erin, but is there anything you’d like to leave with farmers, with agronomists, the audience that’s listening in today?
[00:21:29] Erin Daly:
I love talking about nitrogen, so I could talk about it all day, but maybe what I would say is that N2O losses represent a greater loss of nitrogen from your system. Yes, we are losing 1%, but what’s being missed is that leaky pipe, like you mentioned, there’s multiple nitrogen loss pathways, and N2O losses represent sort of a symptom of imperfect nitrogen use efficiency. We care about nitrogen in the form of N2O, but really, the goal is mitigating nitrogen losses in all forms, and the best way forward to do that, so CanN20Net is still underway. We’re still gathering all this information to improve our recommendations to producers, but the best way forward is really working with an agronomist or developing a 4 R plan that is regionally tailored for your cropping system in your region.
[00:22:20] Erin Daly:
There’s some really cool practices that can be applied that are showing a lot of efficacy preliminarily. A split application, potentially variable rate technology, enhanced efficiency fertilizers, all of these things can really have a place in your nitrogen management.
[00:22:36] Lyle Cowell:
Right, and just following those four Rs, start with right rate. Maybe we could use more soil tests.
[00:22:41] Erin Daly:
I love soil testing. Absolutely. It sounds so simple, but a soil test is really, really critical.
[00:22:46] Lyle Cowell:
Yeah. Find those four Rs on each of your farms out there. CanN20Net is a relatively new program. There’s lots to be learned yet. I believe that there is a website specific to CanN20Net. Is that correct?
[00:22:58] Erin Daly:
Absolutely. It is www.CanN20Net.org. Please visit it. We also have a LinkedIn page where I am trying to figure out my social media literacy, if you will, and trying to keep people engaged with what we’re doing throughout the network. It’s good to check it out, and we also have on our website, you can subscribe to our mailing list and get our newsletter as well.
[00:23:17] Lyle Cowell:
Excellent. We’re talking about science here, science that is deeper than, honestly, I often can understand, but when the rubber hits the road, the agronomists and farmers need to understand what you’ve learned, and following CanN20Net is going to be a very important route, I think, for farmers to take, to just do better on their farm. Again, four Rs include economy. We don’t want to lose nitrogen from the farm.
[00:23:38] Erin Daly:
In terms of last thoughts of what farmers can learn from us, a really huge part of CanN20Net is what we can learn from producers as well. That’s a really critical part of CanN20Net is learning what’s actually feasible on the farm, profitable, and productive as well, because none of these practices are going to be adopted unless a producer sees value in them, which is very valid. What producers can learn from us in terms of best practices and what we can learn from producers at CanN20Net is sort of a two-way street.
[00:24:05] Lyle Cowell:
That is a very good final message, and Erin, I really want to thank you for being on the podcast today. It’s been a great conversation, and for our listeners, I hope you join us next week. In the meantime, if you’d like to check out our website, nutrient-eKonomics.com, and join us again for next week’s episode of The Dirt.
[00:24:24] The Dirt PodKast:
Farming isn’t farming without questions, and now there’s a place to go for answers. At eKonomics, an entire team of agronomists are ready and waiting to help for free. No question is too big or too small. Visit nutrient-eKonomics.com and submit your question with the ask an agronomist feature.
[00:24:46] The Dirt PodKast:
Why are some nutrients mobile in the soil, but not within the plant?
[00:24:51] Karl Wyant:
When we’re thinking about field management, you’ve got scheduling the tractor work, the planter work, the spray work, and now you’ve got to remember which nutrients are mobile in the soil and in the plant. It’s a lot to keep track of, and I think it really underscores the need to have an agronomy friend in your back pocket and make sure that you can rely on someone to answer these kinds of questions.
[00:25:11] Karl Wyant:
When we think about nutrient mobility in the soil, we got to think about chemistry. Some nutrients have a charge on them that allow them to stick to other soil particles, and this makes them fairly immobile. We have some nutrients that are not the charge that will stick to other soil particles and they can kind of move more freely. Got to think about that. When you’re studying for your certified crop advisory exam, you got to memorize these things, and then you got to take it above ground into the plant and think about which nutrients are stuck in plant structures and which ones can be re-mobilized in the plant and moved around into new growth point.
[00:25:46] Karl Wyant:
Think of it like a big four-way table where we have different mobilities below ground and above ground, but to answer the question, what’s an example of a nutrient that’s immobile in the soil and one that’s mobile in a plant? Well, that’s phosphorus. Once you get it in the ground, fairly immobile, but once you get it into the plant, it can move around and be used to go into new growth points on the plant. I’ll just flip that around. A nutrient that’s mobile in the soil, but immobile in the plant. These are some of your micronutrients like boron and manganese. They can move through the soil, but once they’re in a plant, they will stay in a plant structure and they can’t be reused to go to new growth points. So you’ll see the deficiency symptoms on the younger tissues as a result.
[00:26:27] The Dirt PodKast:
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