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Episode transcription:
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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.
If you enjoy the WSU Wheat Beat podcast, do us a favor and subscribe on iTunes or your favorite podcast app and leave us a review so others can find the show too.
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My guest today is Dr. Deirdre Griffin LaHue. Deirdre is an assistant professor of soil health in the Department of Crop and Soil Sciences based at WSU’s Northwestern Washington Research and Extension Center in Mount Vernon. She has been at WSU for five years and works on ways to improve soil functioning and crop productivity across a variety of cropping systems and locations in Washington.
Today, Deirdre will be talking to us about work she is doing on how land application of biosolids affects soils and crop yields in Douglas County, Washington.
Hello, Deirdre.
Dr. Deirdre Griffin LaHue: Hi, there. Thanks for having me.
Drew Lyon: Glad to have you on. So, maybe start off with telling us what biosolids are and how they are being used in Washington.
Dr. Deirdre Griffin LaHue: Yeah. So, biosolids are a product of municipal wastewater treatment, which can make people a little squeamish. It’s basically our poop that’s been processed with processes like anaerobic digestion to meet US EPA standards for land application and other uses. And in Washington state, biosolids are actually classified as a beneficial resource, so biosolids have to be kept out of landfills as much as possible. So, biosolids are actually a really valuable way that we can move nutrients, like nitrogen and phosphorus, from concentrated population areas like, you know, in Washington the Seattle area, for example, and move them back to places where we produce a lot of the food.
An example of this is King County’s loop program. King County does a lot of–they have a great biosolids program and they use the biosolids, which again, are treated and are regulated so that they, you know, they’re meeting standards and they’re using them on things like forestry and in agricultural production in Eastern Washington, which is what I’ve been focusing on.
Drew Lyon: Okay. So, tell us a little bit about the trials you’ve been doing in Douglas County and what you’ve found so far.
Dr. Deirdre Griffin LaHue: Yeah. So, when I joined WSU, I was actually lucky enough to inherit a long-term on-farm trial on biosolids that was started in 1994 by Dr. Craig Cogger and Andy Bary, who were at WSU. And this trial, again, it’s in Douglas County–a very low rainfall zone, usually like a wheat fallow system–and it’s looking at how biosolids can increase crop production in this very low rainfall area. The way it’s set up is we’re looking at three different rates of biosolids that are applied every four years and we’re comparing these to commercial synthetic fertilizers, which are applied every crop year. And we also have an unfertilized control as well.
So, it’s been really valuable to be able to look at this over now, you know, 30 years and see the impact on yields and on soil. So, Andy and Craig found that, on average, the biosolids are really increasing winter wheat yields by around 15% compared to commercial fertilizer, and the difference, interestingly, is even greater with the second crop. So, as a reminder, we’re applying biosolids every four years. But having two crops within that four-year cycle. So, you know, you just get one biosolids application and you get the long-lasting impacts of that nitrogen that’s being released from biosolids.
And so, we’ve been continuing to look at this, and we are continuing to see that there are yield benefits. With all of the biosolids rates, particularly when it’s applied around a three dry ton per acre rate–and now, you know, I’m a soil scientist so as I’ve come on I’m really digging in, so to speak, into more of the soil aspects and looking at things like water holding capacity. The biggest takeaway, I think, is we’ve seen an increase in the soil’s ability to hold on to water, which is really important in this, you know, area that gets about 8 to 10 inches of precip[itation] per year. So, that’s been, I think, a huge benefit, in addition to the nitrogen–the nutrient availability from the biosolids.
We’re also seeing things like less compaction in the soil, which can be really beneficial for increasing root growth.
Drew Lyon: Yeah. I was going to ask you about, you know–you mentioned the nutrients, but are you also increasing organic matter of the soil with this treatment?
Dr. Deirdre Griffin LaHue: Yes. Yeah, we’ve seen definitely increases in organic matter, which can have, you know, multiple benefits. And we were actually–in the last couple of years, we have taken some deep soil cores to look at organic matter, not just in the top, you know, 6 to 12 inches. This is a no till system and the biosolids are being surface applied, so we really see a lot of increases in that topsoil, but we’re also actually seeing increases in organic matter at depth too, which might just be because of increased plant growth from the biosolids–which is really exciting.
And I did want to mention too, that, you know, we’ve had this long-term trial that we’ve learned a lot from and now we’re actually building on it. We started a new trial about three years ago where we’re seeing whether biosolids can help growers do things like integrate grazing into their system. So, for example, maybe they can plant a summer cover crop or let volunteer vegetation come back in the fallow year. And instead of doing like a chem fallow, they can have more biomass from the biosolids and integrate grazing into their systems–which is pretty exciting.
Drew Lyon: Oh, that’s very interesting. Yes. If you can hold more moisture, you might be able to grow crops more intensively, get more crop grown.
Dr. Deirdre Griffin LaHue: Exactly. Yeah.
Drew Lyon: Very good. So, how many acres get biosolids in Douglas County? And how do you determine that?
Dr. Deirdre Griffin LaHue: Yeah. So, through King County’s program—so, they have what’s called the Boulder Park Project, which is in Douglas County, and they work with folks there to spread the biosolids. And there’s about 10,000 acres per year in the county that gets spread and fields get applied roughly every four years. We usually don’t apply a biosolids treatment before that.
And I say we because I’m involved in a lot of screening a lot of the agronomic rates. So, for figuring out how much biosolids should go on a field, we take into account, of course, the crop that’s being grown and the yield goal for that crop–and then, you know, as you would figure out regular nitrogen rates, you know–whether there’s residual soil nitrogen in the spring, nitrate and ammonium and organic matter–and then for each biosolids batch that might come from different municipalities, we know the nitrogen rate, the nitrogen content of that biosolids and the solids rate. And so, we can calculate how many dry tons are needed to be applied to reach the recommended nitrogen rate for that crop based on, you know, work that WSU has done on nitrogen recommendations.
So, the average rate is around three dry tons per acre. So, when a lot of people hear about biosolids being applied to fields, they think, you know, it’s kind of being poured on or, you know, there’s like thick layers, but it’s actually kind of like a sprinkling of biosolids and that three dry ton rate, you know, can be really beneficial for over the next four years.
And, growers have really told me how much of a game changer that this has been for them in the area. One grower, said to me, you know, “If biosolids go away, I’m going to stop farming,” because it’s just been so valuable to them in growing their crops and getting those yield boosts and just improving the soil.
Drew Lyon: You talked about the biosolids actually benefiting the second crop after application more than the first. Is that due to the rate of mineralization of the nitrogen?
Dr. Deirdre Griffin LaHue: Yeah, that’s exactly right. The biosolids kind of keep on giving. In the work that Craig Cogger did previously, he actually found that the yield boost was even greater in that second crop, which is kind of interesting. So, yeah, you’re just kind of continuing to get nitrogen being mineralized from the biosolids.
Drew Lyon: Okay. And what about the cost of biosolids compared to commercial fertilizers? What are we looking at there?
Dr. Deirdre Griffin LaHue: Yeah. So, farmers do pay a little bit to have biosolids applied to their fields, but it actually tends to be much lower than synthetic fertilizer costs. Of course those vary, but they pay roughly $8 per dry ton per acre. And so, if we think about, you know, biosolids vary, but they tend to have about 40 pounds of nitrogen per dry ton, so you’re looking at about $0.20 per pound of nitrogen. So, you know, they’re getting that nitrogen, they’re not having to pay for commercial fertilizer, but then they’re also getting the other benefits that come with biosolids: that increase in organic matter.
Drew Lyon: Okay. Is there any combination of the two: biosolids plus synthetic fertilizers? Say they kind of get a base with the biosolids and then say you get a really wet year and you think your yield potential might be higher, you could spike it with a little nitrogen. Has that been looked at all or are there any growers doing that kind of thing?
Dr. Deirdre Griffin LaHue: Yeah, that’s a great question. There probably are some growers doing that in that second crop, but usually for the first crop, we, you know, we’re just basing it on the nitrogen needs that can be supplied by the biosolids.
Drew Lyon: Okay. And, this work is all done in Douglas County. Is that because of its proximity to where the biosolids are?
Dr. Deirdre Griffin LaHue: Actually, no. The biosolids are being trucked over from the west side and the reason it’s done over there is just the, you know, the amount of acres that are available in that region and the fact that it lends itself really well to, you know, improving soil conditions in these really dryland, you know, semi-arid areas. And there’s just, you know, there’s a lot of space. There’s space for storage of the biosolids over the winter. And so, it just lends itself really well to putting a lot of biosolids and spreading it out over many, many acres.
Drew Lyon: Okay. So, you mentioned earlier that some people think of biosolids and they think, “Yuck!” Are there any concerns with using biosolids for land application?
Dr. Deirdre Griffin LaHue: Yeah. So, you know, there has been a lot of research over the last decade or two on things like levels of heavy metals and pharmaceuticals in biosolids, and, you know, it’s important to remember that it’s really all about what’s coming into the wastewater treatment plant. And, you know, certainly in some situations there can be high levels of these chemicals coming into wastewater treatment, but because that’s been a focus over the last couple of decades, municipalities have worked really closely with, you know, local sources to really reduce levels of things like metals and pharmaceuticals coming in. So, for example, King County, they test their biosolids all the time and their heavy metal levels are now substantially below any regulatory standards, so that’s not really a concern. And they’ve also done things like risk analysis on pharmaceuticals to look at, you know, exposure levels and they’ve shown that levels in their product are so low that it would actually take something like 23,000 years for a farmer to be exposed to an equivalent dose of, for example, an antibiotic, azithromycin. So, you know, certainly something to look at, but people have really been doing good research on that and making sure that it’s not an issue.
And now the focus is really on things like microplastics and PFAS. People have maybe heard about PFAS, it stands for per- and polyfluoroalkyl substances. So, PFAS are a huge range of different polyfluoroalkyl substances and they’re also sometimes called forever chemicals.
And so, now there’s a lot of work going on, in Washington and nationwide to really understand the degree to which biosolids are, you know–what levels of PFAS we are seeing in biosolids and to really understand, you know, how they are being transported in soil and whether they are being uptaken by plants.
And from what I’ve seen, the transport particularly of the more concerning PFAS are very limited in soils and they’re not taken up into plants at all.
But there’s more work that needs to be done on this nationwide. But I will say that in Washington, there’s a lot of sampling going on statewide to make sure that biosolids do not have concerning levels of PFAS. And again, it’s important to remember that biosolids aren’t a source of these chemicals, but it’s really about what’s coming in, so there’s a lot of work to be done also on controlling sources of PFAS to prevent them from getting into water.
Drew Lyon: Okay. Well, you know, long-term studies like this are really important and it sounds like you’re learning a lot from this work. And it sounds like it’s a way for farmers to benefit and for municipalities to benefit, so it’s kind of a win-win situation.
Dr. Deirdre Griffin LaHue: Absolutely.
Drew Lyon: If people want to learn more about this work, what’s the best way for them to look into that?
Dr. Deirdre Griffin LaHue: Yeah. So, I have some information on my website about our research and linking to a lot of good resources, so people can Google soil health NWREC, which is our Research and Extension Center and you can find my page on biosolids. And then, we also have some good Extension factsheets out there. For example, there’s one called “Fertilizing with Biosolids” that has a lot of great information on, you know, different types of biosolids, nutrient concentrations, and considerations for using them for land application.
Drew Lyon: Okay. Where can people find those? Can they find those on your website or do they have to go to the WSU Extension Publications website?
Dr. Deirdre Griffin LaHue: They are linked on my website, and you can also search for them and they’re freely available.
Drew Lyon: All right. We’ll make sure we get those links into our show notes so people can find that information if they’re looking for it.
Deirdre, thank you very much for sharing this information with us. I think it’s really interesting. Again, long-term research like this, you know, that stuff takes a while to really show us what’s happening and it’s really neat that you’re able to dive in and dig into what’s been happening over the last 20, 30 years.
Dr. Deirdre Griffin LaHue: Absolutely. Soil is very slow to change, so it’s really fun to be able to look at how these practices are influencing the soil over the long term.
Drew Lyon: All right. Thank you very much for being my guest today, Deirdre.
Dr. Deirdre Griffin LaHue: Thank you.
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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 lyon@wsu.edu — (drew.lyon@wsu.edu). You can find us online at smallgrains.wsu.edu 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.
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The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.