The Gains of Carbon Change with Dr. Claire Phillips

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Episode transcription:


Drew Lyon: Hello, welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production.

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My guest today is Dr. Claire Phillips. Claire is a research soil scientist with the USDA-ARS Northwest Sustainable Agroecosystems Research Unit. Claire has been in this position since 2022 and is also a co-lead for the USDA Northwest Climate Hub. Her research focuses on soil health, carbon sequestration, and greenhouse gas emissions. The goal of her program is to provide assessments of environmental impacts and technical assistance with conservation practices to whomever might need them.

Today, Claire will tell us more about soil carbon sequestration research at the Cook Agronomy Farm in Pullman. Hello, Claire.

Dr. Claire Phillips: Hello, Drew.

Drew Lyon: So, there’s a lot of talk out there these days about soil carbon sequestration and climate-smart agriculture. What is your research finding about soil carbon sequestration in the Palouse?

Dr. Claire Phillips: Yeah, thanks. There is a lot of talk about soil carbon sequestration and we’ve seen developments over the last four years or so where there’s an actual real flush of programs offering financial incentives to farmers and ranchers that adopt practices that sequester soil carbon. And as you mentioned in the introduction, this area of soil carbon accounting is what I’ve been doing for a long time, so it’s kind of exciting in that I could be useful in this moment where there’s a need for expertise in this particular topic. And, I just want to mention a few of the programs that are animating this conversation in our region. There’s a lot happening, and not everybody knows what all programs are going on.

So, for example, in 2022, NRCS adopted a new conservation practice standard for soil carbon amendment–so, that covers biochar and compost application. The Washington State Legislature developed the Sustainable Farms and Fields Fund, which is intended to help with adoption of climate-smart practices. And then there have been federal investments, too, and University of Idaho was awarded a $55 million grant that most of that money goes to funding producers across the state and across commodities to try out climate-smart practices.

And then there are also private carbon credit companies operating in the northwest. You know, most of those have focused on the Corn Belt, but they are spreading out. And at least, I’ve heard of one that’s operating in Oregon and Washington called the Agoro Carbon Alliance.

So, there’s a lot happening, and everyone’s trying new things. These are new programs. The whole kind of point is to get producers adopting new practices. So, a lot of experimentation. And I have been reflecting on how I can be useful in this moment. And, you know, a lot of the monitoring part about carbon change and about greenhouse gas emissions, that work is done really well and it’s done over a long time periods. It’s really expensive, right–requiring specialized equipment for measuring CO2 and measuring N2O. We want quick answers. And the quick answers are probably mostly going to come from modeling, but what I wanted to lift up today is what we’ve learned from the long-term monitoring–that, you know, best we can do actually go out in the field and measure it kind of thing from Cook Agronomy Farm.

So, the story of carbon change at Cook Agronomy Farm–that site was converted to no-till practice in 1998. And so, we have carbon samples from 1998 and then a decade later, and then 18 years later. And so, here’s what we found at Cook Agronomy Farm. Over the first ten years of no-till adoption, there was buildup of soil carbon in the top six inches, top ten centimeters. But the deeper you go on the profile, the more carbon was actually lost. So, if you look at the top foot–which I mention the top foot, because that’s the depth at which most programs are requiring monitoring and the carbon credit companies are trading on carbon change in the top foot, top 30cm. So, there was a carbon gain still in the top 30cm, but below that depth there is actually carbon loss. And so, if you fast forward 18 years, following no-till adoption, the system actually lost carbon. And most of that carbon was lost below 30cm.

And then there’s one other important thing that we’ve learned from this. So, first decade the site was gaining carbon. And then in 2008, Dave Huggins, our research leader, he made the decision to change the planting implement–so [we] changed the drill from one that had double disc openers to a hoe-type opener, so that somewhat higher disturbance. And when we look at the carbon change after that implement change, we see that the first decade of carbon gains near the surface were then lost, which is a surprise to me. It’s kind of impressive that, you know, both implements which are no-till drills, direct seed implements had such a big impact. And so, what we make from this, I think what we’re learning from Cook Farm, is that the carbon gains near the surface, they can fluctuate.

I guess the other important data set that we have to bear on this is since 2013, we’ve also had this other system that’s measuring CO2, [taking] CO2 direct measurements so we can also get at, “is this system gaining carbon or losing carbon on [an] each year basis?” And those data suggest that year-over-year the system is gaining carbon. So, that says to me that the carbon loss that we measured in the soil may have happened kind of all at once after the change in implement and the system is now gradually regaining carbon.

Drew Lyon: From 1990 through 2012, I managed a long-term tillage plot in western Nebraska. It was wheat fallow. And, so we had no-till, stubble-mulch fallow, and plow black fallow. And in all three of those systems, we were losing carbon over time. So, this study was initiated in 1969, so it’d been running for almost 40 years by the time I left–actually over 40 years. And so, all of those were losing carbon but the no-till is losing it more slowly. And, the gains were all in the surface and as you went deeper, you saw more of a loss. So, if we averaged over that whole foot, we didn’t see any difference between those systems, but we had fallow in there. So, our conclusion was we just didn’t have enough carbon input in that system to even let no-till increase–it just slowed the rate of decrease. And again, at depth, we went down below that top 3 to 6 inches–it actually looked like you were losing carbon compared to a plow where you’re turning it over all the time. So, what are your thoughts about that? Why is that?

Dr. Claire Phillips: It’s really interesting to me. And I think the drum I’m beating on is “let’s keep measuring as deep as we can.” You know, even though there are some forces driving large-scale monitoring towards just the top 30cm, it’s like, “well, if we really want to get this right, let’s look deeper in the profile.”

So, another interesting wrinkle, Ph.D. student Ellen Pang did her dissertation work looking at how sensitive the carbon is to being decomposed through the profile. And she found that carbon in the B horizon—right, so, A horizon, B horizon–it was as or more vulnerable to being decomposed as carbon near the surface.

And that was really surprising to me because, you know, if you radiocarbon date the carbon in the soil, you go down at depth and that carbon is old, like millennia old, right? It isn’t decomposing. And so, I think there [are] perceptions that the carbon at depth is slow to change, you know, and that helps to justify why we don’t need to monitor down there. But her work suggests that, “yeah, even if it’s slow to change, doesn’t mean it’s not vulnerable to change.” So, she took samples and put them in the lab, kind of under optimal respiration conditions and, yeah, the deep carbon was lost in large amounts.

So, why are we losing carbon? Her work suggests that there’s kind of an inherent vulnerability in the carbon at depth and if we look to the hydrology work that’s been done at Cook Farm and elsewhere that points to, “well, you change the moisture regime with no-till adoption, too,” so you shift from a more runoff dominated system to a more infiltration dominated system. That could be helped out by earthworms, right? So, long-term tillage regimes, don’t favor earthworms and if we go to no-till, earthworms can develop these persistent pores.

Okay, so [there are] a lot of things going on there. We could have more infiltration–making it wetter, making it more optimal for decomposition conditions–and that enhanced biology, too, might contribute to the loss of deep carbon.

Drew Lyon: Okay. I remember I did some work when I was in western Nebraska with the ARS group down at Akron, Colorado, and I won’t remember the gentleman’s name–he was kind of a soil physicist-type person–and he did some looking at some long-term rotations there and he found the only place where they were able to store carbon to depth was where they had a perennial grass growing.

So, with the annual cropping, even the more intense systems without fallow weren’t really increasing carbon to depth. It was only the ones that they had basically permanent grasses growing, perennial grasses. Any thoughts about why that might be?

Dr. Claire Phillips: Yeah, I appreciate that. You know, I think, we need to understand what is possible in these dryland systems, right? Like a lot of our ideas about no-till are coming probably more from the Midwest and the northeast and so forth and we might expect less carbon sequestration potential in our region.

Drew Lyon: Okay, so, you’ve been looking at this at the Cook Farm. How do you think what you’re seeing at the Cook Farm might relate to other areas in the dryland Pacific Northwest?

Dr. Claire Phillips: Yeah, I have questions and I have hypotheses, too. I’m really curious if these symptoms of our carbon being vulnerable, if that is a less soil feature, perhaps, because less soils don’t aggregate as strongly and aggregation is really important for protecting carbon. So, that’s a question that would be interesting to follow up elsewhere. But the things you’re mentioning that the carbon gain is kind of tenuous and if we gain carbon, it might be lost.

You know, I want to be clear that that carbon piece is really important when we talk about climate-smart. It’s an important part of the resilience piece and we’re getting more evidence of that all the time that if we restore soils and we build up organic matter, build up soil structure, we build up some resilience to extreme climate and other pressures.

But, from the greenhouse gas perspective, I think we need to come alongside and look at where we can reduce emissions in other areas. And so, my research program is focusing more on nitrogen.

A really interesting example of the impact of nitrogen–from the Pendleton ARS station—so, they did like a complete emissions accounting of alternate systems. So, fallow every other year was one system. Another system was fallow every two years. They had a cover crop system. And one of the takeaways from that was the more frequently that there was fallow in the system, the lower the greenhouse gas emissions overall. And that was because of the nitrogen fertilizer and the emissions footprint of fertilizer. So, that kind of points out this trade off, as you mentioned, more fallow means less carbon coming into the system that can help provide that resilience piece and build organic matter, but it requires nitrogen to grow the crop.

So, the great thing is there’s already so much interest in using nitrogen more effectively, right, because it’s an expensive input.

We have another project going on [that] I’m really excited about. So, I’m collaborating with McGregor to look at one of their nitrogen stabilizer products and they’ve done maybe decades of research on this, but we’re able to bring in the greenhouse gas monitoring piece and see if using nitrogen stabilizers makes a meaningful difference for N2O emissions.

Drew Lyon: Okay. So, carbon, nitrogen–are you observing any other soil changes out of the Cook arm?

Dr. Claire Phillips: Yeah, that is important to mention. So, no-till, you know, it wasn’t meant really to build up soil carbon. It’s really an erosion control measure and at Cook Farm what we’ve seen is erosion basically stopping and we can point to other soil health benefits. Soil pH has been improving, especially at depth. And this story will continue, right?

So, we are up for another sampling in the next year or two, which will be ten years since the last sampling. So, that means I will come back in a couple of years and tell you more about how things are developing there.

Drew Lyon: Okay. Yeah, that’s one of the issues with soil changes is they take a while. I remember I tried to set up a study before I left Nebraska, where we were going to look at intermittent tillage. And so, we were only tilling every six years, I think. But even then, it was going to be like 18 years, we figured, before we really started seeing some differences. And that’s half of person’s career right there. And so, very important work, but not a lot of it done because it does take time.

And, you mentioned earlier about, you know, wanting to make decisions on how are you going to pay a farmer for doing something and they want to see a change in one year. And that’s going to be really difficult.

Dr. Claire Phillips: It is. Yeah, yeah.

Drew Lyon: So, if listeners want to learn more about what you’re doing out at the Cook Farm or elsewhere in the Pacific Northwest, is there someplace they can go to learn more about it?

Dr. Claire Phillips: I’ve been preparing abstracts for the Dryland Field Abstracts booklet, so listeners can check that out. I’ll be out in Douglas County for a field day towards the end of the month talking about carbon markets. We have a CAF LTAR website where we post updates about when we get publications out. And then also we share our findings through the USDA Northwest Climate Hub.

Drew Lyon: Okay. We’ll try to get links to all those into the show notes so listeners who want to learn more can go there and find them more out about it. So, [it’s a] good thing you’re young because you’re going to have to be at this for a while. Very interesting work, and I think a lot of people are going to be very interested in what you learn over the next few years, as well as maybe a decade or two.

Dr. Claire Phillips: Yeah. Thanks, Drew. And I’ll just mention, if anybody is listening, please feel free to reach out to me directly. I don’t know, for instance, what carbon market companies might be operating in the northwest. So, if you’ve got somebody talking to you, feel free to reach out and we can learn together, learn more about it.

Drew Lyon: Great. Claire, thanks for being my guest today on the WSU Wheat Beat Podcast.

Dr. Claire Phillips: Thank you, Drew.


Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcast app. If you have questions or topics you’d like to hear on future episodes, please email me at drew.lyon — that’s — ( You can find us online at and on Facebook and Twitter [X] @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.

I’m Drew Lyon, we’ll see you next time.


The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.