Farm Gate to Field Edge: Tracking Nutrient Efficiency in Dairy Systems

In this episode, Dan Andersen sits down with Dr. Agustin Olivo from the University of Guelph to explore nutrient efficiency in dairy farming. Dr. Olivo highlights adaptive nitrogen management practices from New York. Tune in for practical insights on precision nutrient management and reducing greenhouse gas emissions in dairy systems.

Show Notes

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Dan Andersen: 0:06

Hello and welcome to Talkin' Crap, a podcast by Iowa State University Extension and Outreach. This institution is an equal opportunity provider for the full non discrimination statement or accommodation inquiries, go to www.extension.iastate.edu/legal. In this podcast, we discuss insights into the science technology and best practices surrounding manure management. Our objectives are to build awareness about the challenges farmers and the broader agricultural industry face around manure and to demonstrate solutions and areas of innovation. Hello, and welcome back for another episode of Talkin' Crap. This time we're going to be talking farm gate to field edge tracking nutrient efficiency in dairy systems. And I'm here with Dr Agustin Olivo, who did some great work at Cornell on this very topic. And it's always special when we get to have an out of state guests. So first off, super excited to have you here.

Agustin Olivo: 0:59

Yeah. Thank you very much, Dan. Good morning, afternoon, everyone. And yeah, thanks for having me, and great to be here. to the US to do a master's degree at the

Dan Andersen: 1:09

And then the first thing I wanted to start with is a little introduction of who you are. So I mentioned this experience at Cornell, but walk us through, sort of your history and how you really got into the world of manure. University of Nebraska, Lincoln, where I worked with manure and soil health. That was my first big introduction to manure at UNL and then I moved to Cornell to continue working on nutrient management and greenhouse gas emissions measurement and dairy systems, mostly, which is what we're going to be talking about today. And now, right now, I'm a postdoc at the University of Guelph in Ontario, Canada, where continue working on, mostly on greenhouse gas emissions and soil carbon sequestration in cropping and dairy systems. Awesome. So you clearly found a love for dairy cattle, even though you started out in Nebraska, maybe with very few of them.

Agustin Olivo: 1:54

Yeah, a lot of beef and pork production there, yes,

Dan Andersen: 1:54

yeah. And that's really where I met you. Was when you were at Nebraska.

Agustin Olivo: 1:55

Yep.

Dan Andersen: 1:55

And you probably wondered, do you remember me? Do you remember me? I do obviously, and I thought you're doing great work there, and have been excited to see where you go. So you had two papers published out of your dissertation that that I want to focus on today, and lots of data. You worked with lots of farmers, and really focused on the first one, this farm to field gate sort of nutrient tracking. What's that mean?

Agustin Olivo: 2:18

Yeah. So a lot of my PhD work focused on this, like farm and fuel level indicators for nutrient management, right? And we moved from farm level, farm from gate balances that we called them, which is this whole farm tracking tool for nutrients, mostly nitrogen, phosphorus and potassium, that give us an overall sense as a metric on how farms were doing in terms of their nutrient management. But then a lot of my PhD work focused on developing benchmarks or feasible limits for field level nutrient balances. So those were two different tools that dairy farmers in New York have been using for a while, actually, to check their nutrient use efficiency and see where opportunities for improvement might be.

Dan Andersen: 2:56

Perfect. And when we think about the Iowa manure management system, sort of that whole farm is making sure I have enough land to put on a manure on, and then the field specific one is, what am I going to do in this field? What does it really need?

Agustin Olivo: 3:07

Correct. Yeah, the whole farm one, or the farm gate one, as we call the two, gives you an overall sense of the linkage between the land and the nutrient management and the animals you have in operation. So when farms run this metric and easily see if they get a sense if they have enough land to spread that manure, if they may need to be exporting manure based on a series of feasible limits that our research team at Cornell developed a while ago. Yeah, and then at the field level, it allows us to get a little a sense of like, how efficiently we are managing those nutrients, more for a specific crop. At the field level, exactly, mostly nitrogen and phosphorus.

Dan Andersen: 3:39

Perfect. So nitrogen and phosphorus? Were there big differences between the two? Was there more similarity? What was sort of your experience digging through this data?

Agustin Olivo: 3:47

Yeah. So in general, what we've seen with research in New York is that dairy farms have been doing a great lot of improvement on phosphorus management, mostly through managing better the diet, so we have less phosphorus excretion, and with that, like way more phosphorus that need to be distributed, and they've improved management of phosphorus over time to the point of very much reducing even the fertilizer, like foster fertilizer imports. So I think that's a amazing success stories. Over time, over the last 20 years, they've been improving nitrogen management too, and we see that reflected in farms decreasing their whole farm mass balances, which translates in lowers losses in general, but we still see that they have more challenges, especially with livestock intensification, dairy farms getting bigger and slightly more concentrated, higher animal densities, we see like higher challenges in the air, and room for potential improvement as well.

Dan Andersen: 4:39

And then one of the things on your work that I have a question about is, like phosphorus feels like it's much easier to track. There's no volatile form. Sort of what we bring in has to equal what we go out. Nitrogen just seems a lot more complicated. Have you tried to develop some of these indices. Is that sort of what happened too or...

Agustin Olivo: 4:55

Right. Yeah, like phosphorus in general, yeah, we have less losses, so it's easier to general track, of course, soil test, phosphorus is one of the bigger drivers to define a field needs additional phosphorus or not. And in farms in New York, in my experience, I've been very good at using that as a tool, along with phosphorus indexes, allows us to assess the risk of phosphorus losses. And those two things as a tool to define how much phosphorus to apply or not. Where's nitrogen; we it's more like we tend to lose more so that makes it way more challenging its management. And so there's more room to to buy us. There's more room to like, for producers, to to play around with, like how exactly you need, and way more uncertainty right around it.

Dan Andersen: 5:33

Yeah, that's just what it feels like, way more uncertainty. Now, you mentioned phosphorus indexes, and I know the Iowa one, but I'm unfamiliar with a lot of other states. What does the phosphorus index in New York look like?

Agustin Olivo: 5:43

Right? Yeah, so for phosphorus index in New York is like a system to assess risk, right, on phosphorus losses, and it's formed by a bunch of different characteristics of the field that you assess. And then define a metric or a ranking of your fields, and along with soil test phosphorus, then you define if you the system defines if you can do a nitrogen based application, phosphorus based application, or no manure application, right, based on that risk. And I think that that's really helped that system of combination between risk or P index and soil test P has been like key to to improve management. And one recent development in in New York has been the incorporation of whole farm balances in that framework too, that provide additional flexibility for farms to to be able to manage that. And it's basically, if farms remain in their whole farm phosphorus balances below a threshold for three years in a row, they're able to have more flexibility, because they've shown that at the whole farm level, they are able to manage phosphorus very efficiently. And I think that's pretty it's been a very interesting component of that, of that P index that also values this, this the whole farm management that a lot of farms already doing.

Dan Andersen: 6:51

Yeah, that one sounds really interesting. Ours is based always on sort of this field level, What's the erosion risk? What's the risk of phosphorus movement with that soil, or with drainage water or run-off water? But we don't have this whole farm phosphorus balance necessarily laid out beyond that. So thinking about if a farm showing is roughly in balance, and maybe saying, I don't need maybe as much detail on the fields because of that, that's an interesting idea, and a way to maybe save some time while knowing they're doing the right things for the environment.

Agustin Olivo: 7:15

Correct. And it was a way also to incentivize whole farm phosphorus management, just not thinking the phosphorus management from the field perspective, but also especially in dairy systems, where a lot of farmers feed by-products that may be high in phosphorus, and then incentivizing that whole farm management of phosphorus as a tool like to drive lower losses potentially.

Dan Andersen: 7:32

Going beyond just the risk and trying to get into actually balance or be budgeted for what crops removal are.

Agustin Olivo: 7:37

Exactly. Yes.

Dan Andersen: 7:38

Really nice. That's interesting. And I never didn't know states did that. So that's a really cool sort of indicator for us. So one of the things you talk about in the paper is, oftentimes we'll look at how many acres per cow we have, or how many cows a farm has, as an indicator of maybe what the risk level is. And I think one takeaway I had from the paper was maybe that doesn't tell us as much as we think it is. We have to dive in a little deeper. Could you walk us through maybe some of the more important indicators you found, and what really tells us if farms are doing well or not?

Agustin Olivo: 8:05

Yeah, previous research from our team at Cornell showed that, it was not my PhD work, but previous research on our team showed that when farms, dairy farms in the state of New York, exceed the 1.21 1.2 animal units per acre, an animal unit being roughly about 1000 pounds of live animal weight. When farms exceed that animal's density, they start having challenges managing phosphorus, mostly, and that's when a lot of times, they start falling outside of this feasible limits that our team, for example, define for whole farm phosphorus and nitrogen balances. So that's basically a threshold to take into account, right? And this threshold, like doesn't mean that farms cannot go beyond it, but it kind of hopes to flag that farms, when they exceed that threshold, they may need to consider additional management strategies to be able to more efficiently manage their nutrients. Basically, the most important one, probably, is considering manure experts, how like, more precisely assessing how much, how many nutrients, or how much nutrients we need in the systems, and how much we have been able to export, in case we're like, fulfilling all the nutrients requirement within the system. So that's something that's been shown for dairy farms in New York. So this is state specific, but it's a good indicator, and we see it, and it's, over the years, been confirmed, right? When farms exceed this threshold, they start having more challenges staying within whole farm feasible limit for nutrient balances, and in general, they start having nutrient surpluses, although, as always, it's farm specific, but it's something to keep in mind, something that we discuss a lot with nutrient management planners and farmers at the time I was in my PhD.

Dan Andersen: 9:36

And it doesn't mean you can't, but it like you said, it means that you have to think a little bit harder. It might be a trigger that need solid separation to try and capture some phosphorus, or nutrient separation of some type to work with a neighbor to take.

Agustin Olivo: 9:40

Exactly, to be able to transport it farther and exactly. It's not a nutrient, an animal density type of regulation or things like that, but something to look into and pay attention to.

Dan Andersen: 9:58

All right. Now I want to maybe focus a little bit more on the work you did specific to nutrient budgeting, right on a farm, and I think that's something that people have worked on for a long time, sort of understanding what that was, but you helped give some new perspectives on what makes risk, and especially in manure systems, where I think we have less data, generally, really, what that drives it. And if I read the paper, right, you were working with 900 ish farms or fields of data?

Agustin Olivo: 10:21

Right. We worked for several years with eight Maybe you can do it as long as you do this test, and then you different dairy farms in New York, distributed in different places of the state, and we assessed nutrient balances or nutrient management the field level for about 600 like 560 different corn silage fields, some of them, we tracked them for like, multiple years, two or three or four years even. And so we ended up with a pretty rich data set of almost like 1000 observations across span of my PhD, working like very closely with nutrient management planners and farms across the state. And we learned a lot of things in the main goal of this project was to generate a new framework or create feasible limits, like we, previous people in our team, did for the whole farm balance, but created for the field level balances, the farms could use those feasible limits as a strategy to compare

Dan Andersen: 11:07

That's right.

Agustin Olivo: 11:08

But then like, hopefully, would like allow their performance and most importantly, to using what we took their data and said, well, corn stalk nitrate test end of call the New York adaptive nitrogen management process, farmers to more easily implement this new york adaptive which I can tell you a little bit more about. Basically in New York, like here in Iowa, I imagine farms when exceed like season one, it's a little hard to sometimes be accurate, certain number of cows, for example, in New York is like 300 management process in general, cows, for to be a medium concentrated animal feeding operation, they have to put together a comprehensive nutrient management plan and CNMP, and to do that, they have to follow land grant university guidelines in the state of New York, that's Cornell. And when they do that, those guidelines define exactly how to derive recommendation for nitrogen application, for phosphorus application that we were just talking about. But sometimes farmers may wonder, like, for example, does the yield potential that this Cornell guidelines define is exactly what I'm getting in my field? Like, could apply a little bit more than what those foundational guidelines define? And that's an extremely valid question, because these guidelines are foundational, but the variability is huge, right, as we know, in different fields, so we may want to apply more or test something else. So the New York adaptive nitrogen management process allows farmers to do that, to override those foundational recommendations from the guidelines, Cornell guidelines, but it requires farmers to do two things. One of them is to start measuring yield in those fields to make sure that if, if I believe that my yield may be higher, if I apply, for example, more nitrogen than what the guidelines tell me, then when I want to start recording yield to see if that actually was the case. And the second thing is to start implementing an end of season assessment to see that extra nitrogen that I thought, for example, if farmer believed that they would need more nitrogen for their corn silage crop if to see that extra nitrogen was actually indeed needed. And so far, the New York adaptive management process for that for that assessment required, had a few different options. One of them was the corn stalk nitrate test. So basically, taking a piece of stalk at the bottom of the plan at the end of the season, and if you surpass a threshold of nitrates accumulated in that stalk. I think that test is out of Iowa, out of this university. then what do you do with the availability? Is everyone If you suppress a threshold, then it probably means that you didn't need it that extra nitrogen. But of course, that's assuming the same how do we handle that to a farm specific? pretty labor intensive. New York farms have a lot of fields, and it's hard to track, so we wanted to create an additional framework that would allow farms to implement that end of season And what you did? Correct, and which is related indirectly to assessment, to provide the whole New York adaptive nitrogen management process with more flexibility. And we thought running this balances and defining feasible limits for those balances would be a good way. So farmers go throughout the carbon to nitrogen ratio that affects the availability, the season, they collect all this data, because they need the data on manure applications, yields for their nutrient management plans, and they can relatively easily drive this balances after the season. And if those balances exceed this right? And then for the inorganic fraction of the manure feasible limit with the fine, probably they didn't need that extra nitrogen they were testing or experimenting with. And if they remain within, then that proves that probably they did need it. So the idea was to generate something that would be nitrogen that depends on the manure application method and easier to implement, and they could run over multiple years, because we know that a single season wouldn't be like, Right. So New York, in this nitrogen guidelines, or Cornell extremely precise. timing. If we applied in the fall, actually, the New York's for this nitrogen guidelines, of course, proposes a way to credit Cornell guidelines define no credit to that, because it's those things. And like assumed that a lot of it is going to be lost throughout the winter because of the winter conditions in the state of New York. And then if you apply in the spring, and we give varying amounts of crediting depending on the application method. So basically, if you inject is about 65% of the inorganic

Dan Andersen: 15:41

of solid or liquid manure, essentially. nitrogen will be available for the for the plan that first season. And then if you surface applied, is going to be a smaller number. If you incorporate, like, things vary depending on how quickly you incorporate that basically. Yeah, I think that's a great explanation. One if you're an Iowan listening and you are applying in the fall, just remember that New York winters tend to maybe not be as cold as Iowa's, and we still can probably get some credit from when we put on manure in the fall in Iowa, but it's soil and weather condition dependent, so seeing different states make different assumptions about that isn't a huge surprise.

Agustin Olivo: 16:58

Right? It varies quite a bit from state to state, and I was just reviewing the other day North Carolina's guidelines, and they don't split it up, seems like between organic or inorganic nitrogen. are a few different approaches,

Dan Andersen: 17:07

We don't actually split it up between organic and inorganic nitrogen in Iowa either. Sometimes I think that's for better, and sometimes I think it's for worse. It gives you an easier method. And the reason that that method is still used in Iowa is when they came up with the method, most labs in Iowa weren't measuring the organic fraction. They just told you total nitrogen. So it made a lot of sense then, and I'm a proponent of maybe using that extra information to make a better estimate these days. So one of the things that is interesting, I think, in especially as you try and do field level balances, is yields vary a lot from field to field, and soils might play a big part of that. What was sort of your method, and where did you get to from for budgeting for that purposes?

Agustin Olivo: 17:44

Right. So, in development this framework, we consider, we mostly develop this feasible limits for the field level balances based on what would the balances that would be achieved in this fields if they were to be managed under land grant university guidelines? So Cornell, nitrogen guidelines, right? And this, in this data set, we had a big pool of different fields with different, what we call different nitrogen uptake efficiency. So each of these fields had a different nitrogen uptake efficiency that the Cornell guidelines suggest nutrient management planners to use when budgeting how much fertilizer to apply. So the soil characteristics were indirectly considered through this approach. Right? When we derived the feasible limits, we took into account what efficiencies could be achieved in this field if they were managed under the implementation of beneficial management practices.

Dan Andersen: 18:28

Okay, so when you think about where you got to on your indicator tool, what, what was good, what was meaning a field was working pretty well, what was maybe the threshold where we have to do something different?

Agustin Olivo: 18:36

Right? Using the, again, the Cornell guidelines that apply for New York. We define our threshold to be about 50% for a metric of nitrogen use efficiency, which in our case was nitrogen removed by the corn silage crop over nitrogen available nitrogen supply. Available nitrogen supply is basically the amount of nitrogen that is actually plant available, considering the available factors for manure that we were considering. So that was threshold one in this framework, and threshold two was an actual nitrogen balance. So the difference between nitrogen available, nitrogen supply and nitrogen removed by the crop, and that we settle on a value that was about 142 pounds per acre, which is a value that was derived according to how Cornell recommends farmers right? Nutrient plans in the state, which consider actual, actually soil nitrogen contributions, right? So that what's that's why that threshold may sound a little higher than others that what previously may have reported, but it's because mostly consider multiple sources of nitrogen in this dairy system, so for not just inorganic fertilizer, but also soil, which makes a big difference, and then manure or contributions from rotation credits like alfalfa that may have been grown previous to corn silage in the systems. So those define the framework we created, and that the one that farmers can use to compare their performance to identify if they may have opportunities to improvement or apply it in the context of the New York adapted management process.

Dan Andersen: 20:01

And clearly we want to do as good as we can, but there's some uncertainty from soil credits or legume credits, or even the weather we get in any year, and that sort of threshold is based on we're not going to be perfect. We want to put you in a pretty good spot. I do have one question from you, and I think one of the things you said in your paper is that maybe there was more farm to farm difference in a metric than there was year to year difference.

Agustin Olivo: 20:23

Right. Exactly. That's another thing that we were concerned about when we were driving this framework, is like, Okay, how much does climate, which is something farmers don't manage, is making in this framework? How are we going to define a framework year variability, right? So that pointed at like that, potentially, that opportunity for improvement that some farms may have, and also to the great job that

Dan Andersen: 21:06

Yeah, and I think that's what I wanted to hear. And then that was sort of my takeaway too, is your metrics still work right? They tell us which farms are really getting it right, how well we're doing, and maybe where some other ones have opportunity improvement that year to year variability matters when we're making specific fertilization decisions.

Agustin Olivo: 21:20

Oh, so much. Yeah, totally.

Dan Andersen: 21:21

But for the most part, you're good if you're doing it right, and you can tell which ones maybe are struggling a little bit more to try and get those numbers in focus. And it's not just that you're driving it.

Agustin Olivo: 21:32

Yeah, yeah. This tool was not created to be a prescription tool, right? And it's not, was not created for a farmer to drive a recommendation, right? For that, there is, like, a New York there's a guideline. There is, like, on farm experimentation, that's another thing we and why we developed this framework, because we think that's the ultimate great tool for people to be using, like on farm experimentation, given how natural reality there's in soil, but more of an after end of season assessment to see how we're doing and what potential opportunities we may have to to improve.

Dan Andersen: 21:55

Perfect. So I do want to thank you for joining me today. It's been a great conversation, but I did want to give you a chance for any final thoughts. You might have a recommendation for a dairy farmer or a manure planner on on what to do and how to take best advantage of the work that you

Agustin Olivo: 22:10

Yeah. Thank you very much for the opportunity here. Yeah, I was super excited. And no, I think one thing we learned so this work is the opportunity of value in those alternative nitrogen sources that are already on farm and has so many benefits. We saw the, yeah, there's tremendous potential to use manure very effectively. A lot of nitrogen in that system, a lot of phosphorus. And we also saw, for example, a lot of like, some room for improvement on the how much we credit the nitrogen, like, from legumes in our rotation system. So alfalfa, alfalfa grass mixes. So I think that's another thing that we need to account more precisely and probably have more room to do research on as well. And I think the idea of crediting those on farm sources, sources, and this idea of start tracking all those things to data and putting our farms into context on one end, like potentially identify opportunities for improvement, but also on another end, already document a lot of the great work that farmers are already doing like a lot, because that's another thing that this metrics allowed us to do, is identify where the management is already good, and that can set the path for did in coming up with these indicators. improvement in other areas, but also documenting and communicating that good job that a lot of farms are already doing.

Dan Andersen: 23:14

That's a great point. I think farmers are Thank you for joining this installment of talking crap. Be already doing a great job, and sometimes recognizing that or giving them a way to show that, is a super powerful tool. So thank you so much. sure to take a look at the show notes on our website for links and materials mentioned in the episode. For more information, or to get in touch, go to our website, www.extension.iastate.edu/immag/. If you found what you heard today useful, or it made you think, we hope you subscribe to the show on your podcast app of choice. Signing off from a job that sometimes smells but never stinks, keep on talking crap.