Posts tagged ‘Soils’

Dec 15

Despite Drawbacks, Scientific Collaboration Pays Off

Though collaboration can fuel innovation and increase the relevance and complexity of the scientific questions we study, I’ve noticed it does have its ups and downs. The highs and lows we’ve run into on our research projects may help others avoid some of the pitfalls we experienced as many diverse groups tried to learn how to work together.

Researchers discussing science at the Lytle Ranch Preserve, a remarkable desert laboratory located at the convergence of the Great Basin, Colorado Plateau, and Mojave Desert biogeographical regions.

There can be bumps in the road when collaborating with companies who want to test their product. Being at the forefront of innovation means that untested sensors may require patience as you work out all the bugs together. But from my perspective, this is part of the fun. If we are late adopters of technology, we wouldn’t get to have a say in creating the sensors that will best fit our projects as scientists.

Collaborating scientists can also sometimes run into problems in terms of the stress of setting up an experiment in the time frame that is best for everyone. During our experiment on the Wasatch Plateau, we had six weeks to get together soil moisture and water potential sensors, but our new GS3 water content, temperature, and EC sensors had never been outside of the lab. In addition, we planned to use an NDVI sensor concept that came out of a workshop idea my father Gaylon had. We’d made ONE, and it seemed to work, but that is a long way from the 20 we needed for a long-term experiment in a remote location at 3000 meters elevation. In the end, it all worked out, but not without several late nights and a bit of luck. I remember students holding jackets over me to protect me from the rain as I raced to get the last sensor working. Then we shut the laptop and ran down the hill, trying to beat a huge thunderstorm that started to pelt the area.

Desert-FMP Researchers at the Lytle Ranch Preserve

Other challenges of scientific collaboration present organizational hardships. One of the interesting things about the interdisciplinary science in the Desert FMP project is the complexity of the logistics, and maybe that’s a reason why some people don’t do interdisciplinary projects. We are finding in order to get good data on the effects of small mammals and plants you need to coordinate when you are sampling small mammals and when you’re sampling plants. Communicating between four different labs is complicated. Each of the rainout shelters we use cover an area of approximately 1.5 m2 . That’s not a lot of space when we have two people interested in soil processes and two people interested in plants who all need to know what’s going on underneath the shelter. Deciding who gets to take a destructive sample and who can only make measurements that don’t change the system is really hard. The interesting part of the project where we’re making connections between processes has required a lot of coordination, collaboration, and forward-thinking.

In spite of the headaches, my colleague and I continue to think of ways we can help each other in our research. Maybe we’re gluttons for punishment, but I think the benefits far outweigh the trouble we’ve had. For instance, in the above-mentioned Desert FMP project we’ve been able to discover that small mammals are influential in rangeland fire recovery (read about it here). We only discovered that piece of the puzzle because scientists from differing disciplines are working together. In our Wasatch Plateau project, my scientist colleague said it was extremely helpful for him to be working with an instrumentation expert who could help him with setup and technical issues. Also, we’ve been able to secure some significant grants in our Cook Farm Project (you can read about it in an upcoming post) and answer some important questions that wouldn’t have occurred to either one of us, if we hadn’t been working together. In addition, solving problems that have cropped up in our projects has spurred us on to a new idea for analyzing enormous streams of data in near-real time. (read about it here).

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Dec 3

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TDR versus Capacitance or FDR

When we talk with scientists at conferences they often want to know the difference between TDR versus capacitance or FDR. We’ve written a paper about this in our app guide that has been pretty popular, but it can be difficult to find on our website. Here is an introduction and a link if you are interested in learning more.

TDR Sensor Installation (Giulio Curioni, School of Civil Engineering, Univ. of Birmingham)

Capacitance and TDR techniques are often grouped together because they both measure the dielectric permittivity of the surrounding medium. In fact, it is not uncommon for individuals to confuse the two, suggesting that a given probe measures water content based on TDR when it actually uses capacitance.

10HS capacitance sensor

With that in mind, we will try to clarify the difference between the two techniques. The capacitance technique determines the dielectric permittivity of a medium by measuring the charge time of a capacitor, which uses that medium as a dielectric. We first define a relationship between the time, t, it takes to charge a capacitor from a starting voltage, Vi , to a voltage V, with an applied voltage, Vf. Read more….

Watch the webinar

In this webinar, Dr. Colin Campbell discusses the details regarding different ways to measure soil moisture and the theory behind the measurements. In addition, he provides examples of field research and what technology might apply in each situation. The measurement methods covered are gravimetric sampling, dielectric methods including TDR and FDR/capacitance, neutron probe, and dual needle heat pulse.

Take our Soil Moisture Master Class

Six short videos teach you everything you need to know about soil water content and soil water potential—and why you should measure them together. Plus, master the basics of soil hydraulic conductivity.

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Nov 20

New Applications in Archeology for TDR Probes Measuring Water Content

Recently, I spent a day at the University of Birmingham in the UK where I talked with Dr. Nicole Metje and researchers in the Civil Engineering department. They are working on a project called, “Mapping the Underworld,” (Curioni G., Chapman D.N., Metje N., Foo K.Y., Cross J.D. (2012) Construction and calibration of a field TDR monitoring station. Near Surface Geophysics, 10, 249-261) where they are using TDR probes to help locate buried objects that require maintenance.

University of Birmingham Clock Tower

Currently, people use rudimentary tools to poke around and figure out where the buried object is. A more effective high-tech solution is GPR (Ground Penetrating Radar) that is pulled over the top of the soil and creates a 2D image of permittivity below the ground surface. The problem is GPR only provides relative depth information and must have ancillary data to produce actual values. To address this issue, their group uses TDR probes (time domain reflectometry) which measure dielectric permittivity to ground truth the GPR. Using this method they hope to be able to predict the depth to anomalies that are observed in the 2D GPR output.

Sensor Installation Pit

After working on this for some time, the engineers at the University of Birmingham continue to deal with challenges related to TDR signal, interpretation, and maintenance. One challenge is that TDR systems are complex and power hungry. Thus, the researchers were interested in learning more about soil moisture sensing and different technologies that would help them meet their project goals. My first inclination was to solve their problem with water potential sensors. Many people who work in environmental applications want to know the fate and distribution of water where water potential is the driver. Interestingly, this is one of the few cases where people actually do need permittivity measurements (the value used to derive volumetric water content, VWC) instead of water potential because they use the actual permittivity signal to ground truth the GPR. This realization spawned a four-hour discussion on the frontiers of permittivity measurement in soil and the use of advanced analysis techniques to tease out important soil properties such as bulk density, electrical conductivity, and mineralogy.

I hadn’t given much thought to using soil science instrumentation to locating buried infrastructure. I’m excited to see what the combination of a new technology like GPR and dielectric measurement can do to help us solve everyday problems like where to start digging.

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Nov 10

Solving the Problem of Disappearing Science Lab Technicians

One of the hardest issues university researchers face today is the lack of funding for lab technicians. Although it’s frustrating that universities are no longer able to support this type of personnel, can technology close the gap? This is a question we’ve tried to answer in our Desert FMP project in collaboration with BYU.

Source: Simplyhired.com. Job listings for Science Lab Technicians have decreased 38% from March 2013-March 2014

I was talking to my colleague, Rick Gill, several weeks ago, and he had this to say about the disappearance of the previously indispensable lab technician: “We have fewer people in the lab, and the people we have are more expensive. We need to be deliberate in how we use their time. If we can make the entire system more efficient using technology, we’ll use the people we have in a way that is meaningful. In ecology right now, one of the things that we’re beginning to recognize is that the typical process where the lab tech would go out and take ten samples and average them is not what’s interesting. What’s interesting is when it’s been dry for four weeks, and you get a big rain event. This is because the average for four weeks is really low for almost all processes, but the data three days after it rains swamps the previous four weeks. So the average condition means almost nothing in terms of the processes we’re studying for global change. We need technology to take the place of the technician who would be monitoring the weather and trying to guess when the big events will occur.”

To capture these pulses in the Desert FMP project, we’re using a continuous monitoring system that communicates feedback directly to us as the principal investigators. Using advanced analysis techniques, we can painlessly assure that data are being collected properly and important events are never missed. Although we don’t have a technician, the goals of the project are still being met.

What do you think? How have you dealt with the disappearance of the lab tech?

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Nov 6

Volumetric Water Content: Keeping your Eye on the Goal

Most scientists agree that it’s productive to attend seminars and conferences in order to talk with peers, share ideas, and learn about what other scientists are doing. However, in both academia and industry, we need to be careful that we are not so easily influenced by other scientists’ opinions that we lose sight of the end goals of our own projects. This happened to us recently at Decagon. Here’s the background: our volumetric water content (VWC) sensors actually measure the dielectric permittivity of the soil and use a transfer function to predict VWC from the measured dielectric value. Most of our sensors receive a “dielectric calibration” during the production process where they are calibrated in five dielectric standards to make sure they all measure dielectric permittivity accurately, thus leading to accurate VWC measurements with our standard transfer function.

Volumetric water content (VWC) is determined by measuring the charge storing capacity of the soil using capacitance/frequency domain technology.

We were doing a pretty good job calibrating these sensors in dielectric standards, and our default dielectric-to-VWC transfer function resulted in good VWC accuracy. Then we went to a series of meetings and talked to some of our researcher friends who work on instrumentation. They said, “Look, your water sensors aren’t reading as accurately as they should in dielectric permittivity.” Here’s where the trouble started…

Wanting to make the perfect instrument, we went back and re-evaluated the dielectric calibration standards for these water content sensors and tried to use the book values of dielectric permittivity. This was a bad idea because it fundamentally changed the sensor output. Now, despite the sensors giving a slightly more accurate value for dielectric permittivity, they gave less accurate measurements of VWC. Compounding the problem, we now had a population of sensors that didn’t read the same as earlier sensors of the same type. So when customers started replacing their old sensors they said, “Wait a minute, this sensor reads 4% higher water content than my old water content sensor.” That’s when we realized that we had a real problem.

Our underlying mistake here is that we failed to remember that 99% of the people who buy our VWC sensors don’t even care what dielectric permittivity is. They just want an accurate, repeatable measurement of soil moisture. Essentially, because we were so focused on trying to produce a theoretically perfect sensor for a vocal minority of technically savvy users, we lost sight of the practical matter. Did our sensors produce an accurate water content measurement?

I wonder how often this happens in academia and industry. Scientists are bombarded with input from so many different stakeholders, it’s sometimes difficult to maintain the original focus of their projects. We need to remember to focus on the end goal and filter out things that may distract from that goal.

Download the “Researcher’s complete guide to water potential”—>

Download the “Researcher’s complete guide to soil moisture”—>

Get more information on applied environmental research in our