Transcript:

BRAD NEWBOLD 0:00
Hello everyone and welcome to Office hours with a METER Environment Team. Today’s session will focus on soil texture analysis with our experts Leo Rivera and Shaun Weldon, whom I will introduce in just a moment. But before we start, we’ve got one housekeeping item. If you’re watching this video and you think of a question you’d like to ask our science experts, we encourage you to submit your question on our website at metergroup.com Someone from our science and support team will get back to you with an answer via email. All right, with that out of the way, let’s get started. Today our panelists our research scientist Leo Rivera and Product Manager Shaun Weldon. Leo Rivera operates as a research scientist and director of scientific outreach and METER Group, he earned his undergraduate and master’s degree in soil science at Texas A&M University. There his research focused on the impacts of land use and landscape on soil hydraulic properties. He also helped develop an infiltration system for measuring hydraulic conductivity used by the NRCS in Texas. Currently, Leo leads METER’s collaborative research efforts and focuses on application development in hydrology instrumentation, including the SATURO Infiltrometer and the HYPROP. He also works in R&D to explore new instrumentation for water and nutrient movement in the soil. Shaun Weldon is the product manager for hydrology instrumentation here at METER, he earned his Bachelor’s in environmental science from Western Washington University and his master’s degree also in environmental science from Washington State University. During the 11 years, he’s worked with METER he’s worked in R&D, product development, and now Product Management. Alright, thanks for joining us, you guys!

LEO RIVERA 1:33
Okay, yeah.

BRAD NEWBOLD 1:36
Okay, let’s get started taking our questions, and our first question today. All right, they are asking, why do I need to analyze the texture of my soil? super basic question here.

LEO RIVERA 1:52
All right, well, it’s a good one to get started on, because why are we even here. But there are many reasons and I’m not gonna be able to cover all of them. But most importantly, I mean, that’s your, that’s your starting ground for everything in terms of understanding your soil. Soil texture is is is one of the core pieces that we need to understand when it comes to most soil in agronomic and environmental related questions that have to do with how things grow, behave, what the soil does. It impacts a lot of things, from hydrology, to water retention to even nutrient retention, especially as we start dealing with clays. And there’s many reasons I’m sure, I’m sure we can think of plenty, I don’t know if you have any other thoughts Shaun?

SHAUN WELDON 2:39
I think one of the neat things about texture analysis is not just related to agronomy, or just related to engineering, it covers all of the disciplines that people might use these instruments for, so it’s important to everybody.

BRAD NEWBOLD 2:55
All right. Next question. What methods can I use to do soil texture analysis? And what are the pros and cons of each? Okay,

LEO RIVERA 3:03
Well, I, we probably don’t have the time to get super in detail into all of these methods. We do have a webinar where we cover a lot of these methods. And I highly recommend that you go watch that. So we where we get a little more into the details. And we probably can post the link to that in the description for this for this video. But just to cover the basics. There are kind of three fundamental ways of looking at soil texture, maybe more than that. But of course, you can do it by hand, right? You can texture by hand. And there are ways to do that. And for those of us that have soil judged in the past, we get pretty good at it. But it is something that you have to learn and takes practice and is not going to be super accurate. And then there are tools that are based on the based on Stokes’ Law. And how particle, the power your part, depending on the size of a particle, it’s going to fall out of suspension at a different rate. And so we have tools like hydrometer, pipette, and tools like the PARIO, which we’ll probably dive into a little bit deeper that we can use for that. And then we have also optical methods like laser diffraction, where we use those tools, then there are some other optical messes where we look at things like visible near infrared, and some of those other things. But yeah, I don’t know Shawn, what do you think are the pros and cons of some of these different methods?

SHAUN WELDON 4:34
Well, I think anybody that’s done pipette or hydraulic hydrometer methods, you know, you know, some of the cons there are you have to be there all the time. You have to read it at very certain times. You have to make sure that you’re reading it accurately. One of the things that I don’t like about those methods is that there’s a really high risk of human error just from the readings, whether it’s timing or even just reading the lines wrong And so that’s that’s one of the big cons of it that the Pro is it’s cheap, you get your thing once, and it’s easy, but you need somebody that’s trained, and knows what they’re doing to get really accurate results. As far as like the the laser methods, those, those are pretty accurate, but they’re very expensive. Yeah, the equipment’s very expensive, you use a very small sample, so it’s easy to get something that’s not really representative of your soil type. And so that’s, that’s the con of that one. As far as the PARIO goes, it’s, it’s super accurate, it kind of takes out that human error part that we were talking about. And it also, you know, you’re not, you’re not measuring it based on what you’re looking at. It’s a very, very sensitive instrument that’s measuring it automatically for you, which is really nice. It’s, it’s more expensive than a pipette or a hydrometer. But, you know, I may be biased. That that increase in accuracy and reliability is worth the price.

LEO RIVERA 6:05
Yeah. Another thing that I really love about the PARIO method, and compared to some of the other methods is that you get a full detailed curve of your cell fraction, which is hard to get with three other tools, you can do it like you can do it manually with like the hydrometer, or the pipette method, but it means you’re taking a lot of measurements to get to those points. A con with all of these methods, except for the Vis-NIR maybe or even Vis-NIR needs pretreatment of some sort, is that you have to pretreat your samples. Yeah. And, and that part stinks. Sadly, there’s not really much we can do to get around it. But that definitely is a is a con. But yeah, there’s a lot of literature about these methods. And we go more into detail about the some of the pros and cons of all these methods in that webinar, so I highly recommend checking it out. Yeah.

BRAD NEWBOLD 7:00
All right. This next question here; can the PARIO be used to determine particle size of silt in stream samples?

LEO RIVERA 7:09
Yeah, that is a really good question. And not something that any of us have tested? Um, I know, I understand the concept. And and I know that we use similar principles like you can use a hydrometer to figure that out. But my concern is that depending on the amount of silt that’s in suspension, is that it might actually be too small to even detect yet the PARIO.

SHAUN WELDON 7:36
I think, with the PARIO Plus, you’re going to have a better chance than you would with the older methods, because you do take that small sample and weigh that in the oven. There’s particles that are still in suspension. But I think I worry that you’d be using such a small amount of those particles that it would be easy to introduce a lot of air. Yeah, in those readings.

LEO RIVERA 7:57
Yeah. Yeah, that might not be the best application for the best tool for this application. But hey, prove us wrong. I’d love to love if anybody goes out and researches that and actually tries it out. I love to learn about how that experience went and if it actually worked, and if that’s the case, we can definitely work together to learn more about how to how to actually use these tools for that methodology.

BRAD NEWBOLD 8:23
Okay, this next question is asking, how accurate does a soil texture analysis have to be? What are the consequences of a less accurate analysis?

LEO RIVERA 8:35
Thats a good question.

SHAUN WELDON 8:36
Yeah. The first thing that comes to my mind is, how accurately do you want to understand what’s happening in your study area? Yeah. I think that that getting getting a general picture is good for some things. But for most applications that people are going to be using, they’re going to really want to know, I think, most importantly, how water is moving through there, how nutrients might be moving through there, and how well, plant roots are going to be able to get through the soil. And so the more accurate you are, I think the better

LEO RIVERA 9:09
Yeah, yeah, I mean, it almost always ultimately comes down to what your research goals are. And, and so I don’t know if I can tell you specifically how accurate you need it to be. It’s really up to you and your research goals. But ideally, we’re going to use the best tools possible to get an accurate measurement. And I would say, seven times out of 10, you’re probably going to want to try to be as accurate as possible with your measurements because, you know, a three to 6% error in your clay content. estimation, potentially could be significant depending on what you’re doing. And especially depending on the soil type that you’re measuring in. So yeah, choose wisely.

BRAD NEWBOLD 9:57
Right, next question in What situations would I need to complete soil particle distribution curve versus being able to get away with a partial one?

LEO RIVERA 10:07
Yeah, that’s a really good question. To be honest, I don’t think people fully understand the value yet of having a full particle size distribution curve. Now, people often just look at soil texture in terms of what’s my percent sand, what’s my percent silt, and what’s my percent clay. But in reality, you’re silt fractions, a wide range, your sand is also a pretty wide, wide range. And, for example, if you have a lot of very fine sands, in your soil, they often tend to behave more like silts, then then of course, then of course, sand does. So understanding that actually can be really valuable, especially when you’re trying to understand physical and hydrologic processes in your soil and how the soil is behaving. So there’s a lot of literature that’s coming out that showing how useful a detailed soil particle distribution curve can be. And, and so I think there’s a lot to be learned about what we can can get out of it, just like we’re learning more about soil moisture release curves. So so obviously, a lot of people are gonna be fine with just sand, silt and clay. But I think there’s a lot of value in it.

SHAUN WELDON 11:23
Yeah and I think it kind of goes back to what you’re talking about earlier of having the most accurate data, having that most accurate view of what you’re looking at. Because if you say sand to one person, somebody’s gonna think like playground sand you know think very very coarse. And when we’re looking at some of these, like you’re saying, it’s, it really does behave differently than that. Yeah. Because it is such a wide range.

LEO RIVERA 11:44
Yep. Yeah. So, you know, the more it’s always, always think about it like this, you can collect this information and have it now it’s a lot easier to have all that detailed information, and maybe not need it. But if you in the future, you realize, oh, I need that information, but I don’t have it, it’s a lot harder to go back and get it. And you might learn more about some of the different research questions that you’re looking at just because you have this information. So anyways, I think it’s important, and we’re learning more and more every day about the actual importance of a detail soil particle distribution, soil particle distribution curve.

BRAD NEWBOLD 12:24
Alright, this next question is asking about applications. So they’re asking, would a grower need the accuracy of a PARIO? Or would another method be suitable? What applications is the PARIO well suited for?

LEO RIVERA 12:38
Oh, great question. Um, you know, it’s hard to say from a grower perspective, if this is something that they’re going to need. But I would say from a consultant perspective, if I’m working with a grower, I think it’s important to understand this a little bit more deeply, and have this accurate, you know, have tools that are going to be more accurate and give me more detailed information. Yeah, because again, even in growing applications, the small subtle differences can make a difference.

SHAUN WELDON 13:04
Especially on a crop that’s very sensitive to say, for example, drainage. Yeah, that needs a really well drained soil. If we go in there with something that’s not as accurate, and we give a soil texture that might not be that accurate soil, the plants and the crop yields can suffer quite a bit. Yeah. So I agree. I think it’s, I think it’s really important. Yeah.

LEO RIVERA 13:25
No, I mean, I think the PARIO is well suited for several applications. I’m a soil scientist and so, of course, the party is well suited for the work that we do in soil science from looking at, you know, doing physical analysis of soils. And then using that to understand some of the hydraulic, you know, hydraulic, hydraulic properties. It’s also well suited for engineering. Yeah. And, and getting all that information. I mean, like you said earlier, Shaun, there’s just so many applications where we need to understand this information.

SHAUN WELDON 13:57
Yeah. And I mean, some of my background stuff, we did a lot of habitat restoration stuff. And that’s, that’s really important when you’ve had, you know, land that’s been used for other things. And you’re trying to restore that back to make sure that you’re getting suitable habitat for the native plants that were there before. And so I think that, like you said, it just, it covers such a wide range of applications.

LEO RIVERA 14:18
Yeah, exactly. Yeah. So I think there’s a lot of opportunity out there for use of tools like the PARIO. And it just depends on on what you’re trying to look at.

BRAD NEWBOLD 14:30
Okay, next question. How long does a PARIO or measurement take and how many PARIO’s can you hook up to one computer?

LEO RIVERA 14:38
So I’m gonna let you take this one.

SHAUN WELDON 14:39
So this this is a great question. I think one of the exciting things about the PARIO was that it is a lot shorter the actual measurement time. Right now the measurement time takes anywhere between about two and a half to three hours. That doesn’t include your you still need to do the same kind of pretreatment stuff that we do with all the other applications. But once that’s all ready and plugging it in and starting, it’s about two and a half to three hours before you take a small sample. And when you put that in the, excuse me the oven overnight, and then you do your you still have to do your sand saving, just like with any other method. So there’s there’s definitely time and that time is going to vary based on your soil for that pretreatment in that post treatment, but the actual measurement is actually really quick.

LEO RIVERA 15:21
Yeah, yeah. Which is pretty crazy to think about. I mean, for those, I mean, a lot of us have gone out and done the traditional hydrometer method, the 24 hour measurement. And we all know how long that takes. And the fact that we can get better accuracy of plus or minus half a percent accuracy in to just little over two hours is is pretty amazing. And so it’s, it’s pretty neat to think that we can do that. And I think on there, how many PARIOS? Can we hook up now to a computer?

SHAUN WELDON 15:53
With our new LABROS soil view software, you can put 20 units up, I do want to put on there. I do want to say on there that if you’re putting more than about two, you want to make sure you’re using a powered USB hub. Because it does pull usually too much power for a normal USB hub, and you’ll lose communication. Yeah, the software will support up to 20.

LEO RIVERA 16:13
It’s a lot of soil, soil texture analysis measurements.

SHAUN WELDON 16:16
Yeah.

BRAD NEWBOLD 16:18
All right. This next question asks, What about the pretreatment of samples any advice for the organic matter destruction?

LEO RIVERA 16:28
Yeah, well, great question. And I just want to start off by saying that pretreatment is still by far one of the most important steps that you’re going to take in order to get an accurate particle size analysis measurement. Because if you don’t pretreat your samples, well, then you’re going to have samples that are either bound together or other things that could interfere with the measurement, so they’re super critical.

SHAUN WELDON 16:48
Yeah that makes or breaks your measurement. Absolutely.

LEO RIVERA 16:51
Yeah. So when we’re thinking about pretreatment, there’s three main areas that we need to pretreat it’s dispersion. And then iron oxides, and organic matter, right? I’m probably missing some other stuff in there.

SHAUN WELDON 17:04
So currently, we list the salt destruction. Yeah, as an optional one, and iron is going to be very dependent on your your soil as well, right. But one thing or two things I guess everybody needs to do or that dispersion and the organic matter destruction.

LEO RIVERA 17:19
Yep. Yeah, those are the most important. And there are several different ways to approach. You know, especially when you’re thinking about dispersion in organic matter destruction. Although I think the organic matter destruction, there’s one primary way to do that with with hydrogen peroxide. But pretreatment like for the dispersion, well, there’s typically you need to do two steps, you have the physical and the chemical dispersion. And you always start with the chemical dispersion. We typically use sodium hexametaphosphate. There are other dispersants out there that people use as well. There’s ASTM methods, and then there’s din methods as well, that sometimes slightly differ. And then methods of soil analysis has, I think, some different options in there as well. I think sodium in the US, sodium hexametaphosphate, is probably the most common that I can think of, that’s what I’ve used. And then for physical dispersion, we use either a shaker table, or the milkshake mixer approach. So and then I don’t know, Shaun, what about organic matter?

SHAUN WELDON 18:29
I, you know, I’ve I’ve always done the hydrogen peroxide, because I think it does a better job. And it, it also kind of leaves your soil more in a natural form than baking it or things like that. Yeah. Some people like to like to bake it to kind of burn off the organic matter. In some soils that can kind of lead to some hydrophobic behavior, which I don’t like to see. So for me, it’s always been hydrogen peroxide, in places in soils that do have a high organic matter content, then that can get messy and take some time. But I think just just being there and making sure you’re keeping an eye on it usually takes care of all those issues.

LEO RIVERA 19:10
Yeah. Yep. No, definitely not take care of that. I can’t remember what is the what is the minimum? Is it one and a half percent organic matter that? Yeah, if it’s below that, then you don’t have to pretreat for organic matter. But in most soils, hopefully, we have more than especially at the surface, hopefully, we have more than one and a half percent. But in many cases, we do see soils that that don’t have that.

SHAUN WELDON 19:33
And I think for me, just as a best practice, it’s good to just do it anyway, right? Because I want to make sure that if I’m spending the time to do all this pretreatment and take the readings that I want them to be as accurate as possible.

LEO RIVERA 19:44
Yeah. Take the time patients. Yep.

BRAD NEWBOLD 19:50
All right. This next individual also is asking about dealing with organic matter with hydrogen peroxide. They’re having challenges with that kind of pretreatment as well. You you have any insights that they are asking specifically for working with volcanic areas with very clay soils? So any, any thoughts or insights or help for them?

LEO RIVERA 20:09
Yeah, I mean, it’s it again, it’s just, it’s the method that you have to work with those soils. But the big challenge with volcanic soils is not just the pretreatment, but that the soil actually has some physical differences. Volcanic Volcanic soils tend to have more allophane content in the minerals are more more allophane as a mineral. And because of that, they are actually there, their physical characteristics are different, your particle density is different. And so you have to account for that. But outside of, of that, I think you have, there’s really no better way for the pretreatment other than the peroxide or maybe the burning but…

SHAUN WELDON 20:52
yeah, I think for my experience with some volcanic soils, there’s been very little organic matter content left in those, for the most part. So I haven’t had a lot of challenges with that. Personally, we did a little bit of work with some volcanic soils from around Mount St. Helens when I was doing undergrad stuff. And so those ones, they, they didn’t have a lot of organic matter in those ones that were the purely volcanic stuff. So I think just doing that hydrogen peroxide and keeping an eye on it is is kind of what you got to do.

LEO RIVERA 21:26
Yeah, we didn’t have to deal with volcanic soils in Texas. So it’s more of a Washington thing.

BRAD NEWBOLD 21:35
All right this next one, are there any scanning techniques available for texture analysis?

LEO RIVERA 21:43
Yeah, that’s a great question. I didn’t make I guess it depends on what your your your, you know, what you define a scanning? I mean, that laser diffraction is is, I guess, would technically be a scanning method. Yeah. And it definitely works well. And one of the challenges with laser diffraction, though, is clay particles are not round they’re flat. And depending on the angle at which the laser is looking at the clay particle, it could induce some error in your clay fraction analysis, because it’s going to look like a bigger particle than what it actually is. But, yeah, that’s a common scanning technique, I guess, that I could think of.

SHAUN WELDON 22:26
Yeah, as far as I’m not sure if they’re asking about remote sensing. But as far as remote sensing goes, there’s really not a good method for doing texture analysis remotely. Especially in places where you do have a lot of different soil types really closely related or different depths. There’s just really not a good way to do that in a remote setting, yeah.

BRAD NEWBOLD 22:52
All right. Next one. Can we use speaking of remote sensing? Can we use satellite derived products or Vis-NIR spectroscopy with the same level of confidence as a pipette method? Which method is going to be more popular in the future?

LEO RIVERA 23:08
That’s a good question, I am not aware of any satellite derived products that we can use to estimate soil texture, maybe there’s some out there that I’m not aware of, I’m not an expert in satellite measurements. Vis-NIR for sure, can be used to make these measurements, but you cannot have the same level of confidence. And when you say confidence, its accuracy as a pipette. method. And, but it’s a great tool for quick analysis and quick scanning of soils to get some of those properties. Vis-NIR depends on the model behind it just like a lot of these optical methods like that, but it’s a good approach.

SHAUN WELDON 23:48
Yeah so I think in the future, we’re probably going to see more of that used. But I think that we’re still going to be using these traditional methods as well, to kind of ground truth, the things that we’re seeing on there, we see that a lot even now with, with satellite imagery of other measurements of environmental measurements. We look at these and then we still want to make sure that we’re actually seeing accurately on the level that we want to see with by ground truthing it with other sensors.

LEO RIVERA 24:14
Yeah, no, I think we’re seeing a lot of of use of some of these methods Vis-NIR in, I think it was at mid near infrared measurements as well. You’re seeing seeing a lot of use of that for for these types of measurements. And they are super powerful tools, because you can do a lot of measurements really quickly. Again, they’re never gonna I don’t anticipate they’ll ever have the same level of accuracy that you can expect from some of these traditional methods. But again, I’d love to be proved wrong.

SHAUN WELDON 24:40
Yeah.

LEO RIVERA 24:41
And see some of these methods turn out to be more accurate than than what we’ve received them being.

BRAD NEWBOLD 24:49
All right. I think this is going to be our last question for the session here. And they are asking what do you guys do with saline soils with particle sedimentation due to flocculation generated by excess salts?

LEO RIVERA 25:09
Great question, I’m gonna let Shaun take that one.

SHAUN WELDON 25:11
So we do have, that’s one of those four areas that Leo was talking about earlier that we do pre treatments for if if your soil has a lot of salts in it, there’s a section in the manual that does talk about removing salts. And the basic structure or the basic process is that you’re just going to be rinsing the soils, putting it into a centrifuge to kind of pull that water out of the soil matrix there. And you’re going to do that a couple of times until you that EC, the electrical conductivity of that liquid is down to an acceptable level. That’s basically what you’re going to do. I do want to kind of put a little plug in here we are getting some videos for these pretreatment methods that we’re making right now. I’m hoping they’re going to be out here in the next couple of months, maybe by the first of the year, that kind of go over these these processes that we’re talking about. The manual is very detailed and has really great information on this. Having a little video to go along with that. So it was a good help.

LEO RIVERA 26:11
Yeah, yeah, it’s a lot of these things can be dealt with their correct pretreatment. Yeah. And but sometimes you just have to be patient and take the time to do the pretreatment. Which sucks sometimes, because it is, you know, it’s more work you have to do to get to these measurements. But, you know, we want to be accurate with our measurements. So let’s take the time to do the work that needs to be done to get that way.

SHAUN WELDON 26:33
Absolutely

BRAD NEWBOLD 26:36
All right. Any final thoughts or insights on soil texture analysis, you guys things that we missed or didn’t cover.

LEO RIVERA 26:43
I don’t think we necessarily missed anything, I just, you know, I can remember back to doing hydrometer method, or hydrometer measurements in grad school, and trying to process several 100 samples and what that was like, and these tools have come a long way. And, and it’s fun to work on these things and see where we’re gonna go, I’m really excited to see where we continue to push these tools. In the future. We have lots of crazy ideas on how to continue to improve these measurements. And that’s a fun part of what we do here is experimenting and trying to make these measurements better.

SHAUN WELDON 27:19
Yeah and I would just add that, you know, we do really love this stuff. So if you have questions or, or data that you want to send in and have us look at, we’re always happy to do that. We do really enjoy this and I think getting really accurate measurements and getting these these really detailed readings can really help your research or your you know, whatever your desert you’re working on. So yeah.

BRAD NEWBOLD 27:48
All right. That’s gonna wrap it up for us today. Thank you again for joining us. We hope you enjoyed this discussion. Thank you everybody for the great questions. And again, if you have any questions that we didn’t answer, please contact us via our website metergroup.com finally, you can subscribe to the METER Group YouTube channel and accept notifications to see previous episodes of office hours and to get notified when future videos are available. Thanks again. Stay safe, and have a great day.