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Best of 2019: Environmental Biophysics

In case you missed them, here are our most popular educational webinars of 2019. Watch any or all of them at your convenience.

Lab vs. In Situ Water Characteristic Curves

Lab-produced soil water retention curves can be paired with information from in situ moisture release curves for deeper insight into real-world variability.

Watch it here—>

Hydrology 101: The Science Behind the SATURO Infiltrometer

Dr. Gaylon S. Campbell teaches the basics of hydraulic conductivity and the science behind the SATURO automated dual head infiltrometer.

Watch it here—>

Publish More. Work Less. Introducing ZENTRA Cloud

METER research scientist Dr. Colin Campbell discusses how ZENTRA Cloud data management software simplifies the research process and why researchers can’t afford to live without it.

Watch it here—>

Soil Moisture 101: Need to Know Basics

Soil moisture is more than just knowing the amount of water in soil. Learn basic principles you need to know before deciding how to measure it.

Watch it here—>

Soil Moisture 201: Moisture Release Curves—Revealed

A soil moisture release curve is a powerful tool used to predict plant water uptake, deep drainage, runoff, and more.

Watch it here—>

Soil Moisture 301: Hydraulic Conductivity—Why You Need It. How to Measure it.

If you want to predict how water will move within your soil system, you need to understand hydraulic conductivity because it governs water flow.

Watch it here—>

Soil Moisture 102: Water Content Methods—Demystified

Dr. Colin Campbell compares measurement theory, the pros and cons of each method, and why modern sensing is about more than just the sensor.

Watch it here—>

Soil Moisture 202: Choosing the Right Water Potential Sensor

Electrical conductivity

METER research scientist Leo Rivera discusses how to choose the right field water potential sensor for your application.

Watch it here—>

Water management: Plant-Water Relations and Atmospheric Demand

Dr. Gaylon Campbell shares his newest insights and explores options for water management beyond soil moisture. Learn the why and how of scheduling irrigation using plant or atmospheric measurements. Understand canopy temperature and its role in detecting water stress in crops. Plus, discover when plant water information is necessary and which measurement(s) to use.

Watch it here—>

How to improve irrigation scheduling using soil moisture


Dr. Gaylon Campbell covers the different methods irrigators can use to schedule irrigation and the pros and cons of each.

Watch it here—>

Next up:

Soil Moisture 302: Hydraulic Conductivity—Which Instrument is Right for You?

Leo Rivera, research scientist at METER teaches which situations require saturated or unsaturated hydraulic conductivity and the pros and cons of common methods.

Watch it here—>

Predictable Yields using Remote and Field Monitoring

New data sources offer tools for growers to optimize production in the field. But the task of implementing them is often difficult. Learn how data from soil and space can work together to make the job of irrigation scheduling easier.

Watch it here—>

Learn more

Download “The researcher’s complete guide to soil moisture”

Download “The researcher’s complete guide to water potential

Founders of Environmental Biophysics: Champ Tanner

Champ Tanner (November 16, 1920 – September 22, 1990) Image:

Champ Tanner (November 16, 1920 – September 22, 1990) Image:

We interviewed Gaylon Campbell, Ph.D. about his association with one of the founders of environmental biophysics, Champ Tanner.

Who was Champ Tanner?

Champ Tanner was a dominant scientist in his time and a giant among his colleagues.  He was the first soil scientist to be elected a member of the National Academy of Sciences: the highest honor a scientist can achieve in the United States.  Some may not realize that throughout a career filled with achievements and awards, he battled the challenges of a debilitating illness.  He didn’t let that limit his passion for science, however.  His efforts to understand and improve measurements generally went beyond those of his fellow scientists.  One of his colleagues once said of him, “Champ’s life exemplified goal-oriented determination and optimism regardless of physical or financial impediment.”

Dr. Champ Tanner was one of the pioneers in applying micrometeorology to agriculture.

Dr. Tanner was one of the pioneers in applying micrometeorology to agriculture.

What were his scientific contributions?

Champ was an extremely careful experimentalist who was gifted at developing instrumentation.   He started out making significant contributions in soil physics such as improved methods for measuring water retention, particle size distribution, air-filled porosity, and permeability.  He was one of the pioneers in applying micrometeorology to agriculture and was passionate about finding ways to improve the precision and reliability of measurements.  No measurement was too difficult.  He designed and built his own precise weighing lysimeters which provided measurements of evapotranspiration in as little as 15 minutes.   Later, he switched to plant physiology, reading almost every published paper on the subject and then building his own thermocouple psychrometer and plant pressure chambers, making important contributions in that field.

His largest contribution, however, was the measure of excellence he inspired in the students that he trained.   I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have.  They’ve all made enormous contributions in many different fields.  Perhaps it was because he was a pretty hard taskmaster.   He expected the students to meet a standard, and the ones that struggled with that had a hard time. In fact, to this day one former student complains, “About once a year, I have a nightmare in which Champ appears.”

Champ Tanner

I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have.

Champ wanted his students to measure up, but he also cared about them.  His fellow scientist, Wilford Gardner, described him this way, “There was a transcendent integrity to his personality that permeated everything he did.  He could be blunt, candid and forthright, but he was never lacking in compassion and concern for students, colleagues, and friends.”

What was your association with him?

I had a wonderful relationship with Champ, although I wasn’t one of his students. One of his former students came to WSU as a visiting scientist and told him about what I was working on.  As a result, he brought me into his inner circle of associates and played a vital role in the success of my research.  This association even extended to my family who were with me on one of my many trips to Madison. Despite my numerous and occasionally unruly progeny, he and his wife welcomed us like long lost relatives and made each of the children feel special.  That’s who they were: the most caring and outgoing people.

Champ also had a sense of humor.  He used to call me up to have long discussions about science, and because he was two time zones ahead, it would get pretty late for him. We’d be having an intense discussion about experimentation, and all of a sudden he’d stop and say, “Oh, I’d better cut this off, or I’ll get home to a cold supper and a hot wife.”

What kind of a person was he?

If you worked in his lab, you needed to tow the mark.  You didn’t leave tools around, and you didn’t mess them up. If you left out a screwdriver, you’d find it on your desk the next morning with a terse note.  And if you took the diagonal pliers, cut some hard wire with it and left some nicks, those would be on your desk too. It was a sort of tough love, but he used it to train his students to the highest possible level.  

Champ Tanner

He taught his students to be rigorous in their measurement protocols

He wanted his students to stand up and argue for their point.  If you were the kind of person that could stand your ground and put up a good defense, he loved that.  Gardner described Champ in this way, “His work hours were legendary.  His standards of science and personal integrity were almost unrealistically high.  The stories his students now pass on to their students may sound apocryphal to those who did not know Champ.  But it was impossible to exaggerate where Champ was concerned.”

What do you think scientists today can learn from him?

What we can learn from Champ Tanner is not to fool ourselves.  He thought you should try to come to an answer in a few different ways, to be sure that it really was the answer. He taught his students to be rigorous in their measurement protocols in order to get the noise out of their experiments.  He wanted them to dig to the bottom of problems and understand the details.  In his mind, you couldn’t be a scientist and rely on somebody else to figure out heat transfer or radiation. He thought you should understand it well enough that you could defend it yourself.   

You can read more about Champ Tanner’s life and scientific contributions in this biographical sketch, written for the National Academy of Sciences when he died.

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

Get more information on applied environmental research in our

Using Soil Moisture Sensors on Humans?

Dr. Stuart Campbell, professor of Biomedical Engineering at Yale University has been toying with the idea of using soil moisture sensors to measure tissue edema in human subjects.

soil moisture sensors

Tissue edema occurs when too much fluid leaks from your capillaries into your tissue.

He says he got the idea from Dr. Ken Campbell, former professor of Bioengineering at Washington State University:  “I was explaining to Dr. Campbell about the sensors METER makes, and he pointed out that there are many diseases where you might want to measure someone’s tissue edema, and it would be interesting to see if you could use a soil sensor in a wearable device to help doctors monitor swelling in their patients, much like a heart monitor monitors heart activity.”

Tissue Edema:

Tissue edema occurs when too much fluid leaks from your capillaries into your tissue. Capillaries, the smallest blood vessels in your body, are somewhat leaky, allowing the exchange of nutrients and waste between the tissue and the blood. The fluid that surrounds the blood cells is free to exchange across the capillaries, and edema will occur when too much fluid leaks out of the circulatory system into the tissue.  Edema can be caused by things like heart disease, pregnancy, or standing on your feet all day.  

What Makes the Fluid Leak?

In soil, water moves from high water potential to low water potential. Similarly, there are forces inside the circulatory system that cause the transfer of fluid between capillaries.  Your blood vessels have a certain amount of pressure that is generated by your heart.  If your blood pressure goes up, it can cause edema. Dr. Stuart Campbell says, “The actual fluid pressure is part of what decides how much fluid is pushed out, but it’s not that simple. Your blood has large proteins that are too big to get out of the capillary. That means the more water that leaves the capillary and moves into the tissue, the more concentrated those proteins become, which lowers the water potential (or osmotic potential) of the blood. This delicate balance is what prevents too much water from leaking out.  However, if you have a disease that tips this balance, either through high blood pressure or a condition that allows those proteins to leak out of the capillary, edema would occur because you don’t have the osmotic potential pulling the water back into the capillary and keeping the proper balance.”

soil moisture sensors

Dr. Campbell thought it would be interesting to figure out if he could monitor the edema of heart tissue during one of the procedures.

The Heart Experiment:

Dr. Campbell decided to see if a soil sensor would work to measure animal tissue when he was working as a summer student in the Visible Heart Lab at the University of Minnesota.  Campbell says, “Similar to a human heart transplant, this lab is able to keep pig hearts alive outside the body.  The problem, however, is that they use a manmade solution instead of blood, and that imitation blood is not ideal. If the composition of the fluid is not perfectly adjusted, you can have problems with your experiments.  I thought it would be interesting to figure out if we could monitor the edema of the heart tissue during one of the procedures. I hooked up the soil probe and used it in one experiment where I put it in contact with the heart while it was beating.  There was, in fact, a change in output of that signal during the experiment.  But, because I only got one chance at it, it was inconclusive as to whether this was indicative of an imbalance in the composition of our artificial blood substitute.”  

An Anecdotal Experiment:

Still curious to see if the idea would work, Dr. Campbell decided to try one more experiment: this time on his wife who was experiencing edema symptoms after childbirth.  He says, “It occurred to me that this was an opportunity to try out the soil moisture probe one more time to measure tissue edema.  So each day, I would measure her ankles, putting the probe in flat contact with her skin while tightening a strap gently.”  Dr. Campbell says he watched the swelling go down as the numbers on the probe got smaller, and comments, “It was anecdotal evidence that at least in extreme cases, you might be able to get the soil probe to work.  But I still have questions, such as, how would you make sure that the probe was always touching the skin in the same way?  And, if the person got sweaty, would that change the soil probe reading?”  

Soil Moisture Sensors

There are millions of people in this country who have heart failure.

Why the Experiments Should Continue:

Though Dr. Campbell hasn’t had time to pursue the experiment further, he feels that if the idea works, it has the potential to improve lives and save our nation billions of dollars.  He says, “There are millions of people in this country who have heart failure.  Maybe they’ve had a blockage in one of their coronary arteries, or perhaps their heart is worn out because of age. You can tell when someone is in heart failure because when they lie down to go to sleep at night, all that fluid makes its way slowly from the ankles, through the legs, the torso, and eventually into the chest. The problem is that the lungs are very delicate, and when you have edema in the lungs, it’s almost like you have pneumonia.  This type of sensor could be an easy way for people to monitor themselves and manage their fluid intake and diet after they get home from the hospital.”  Dr. Campbell says this helps the economy because if people don’t manage their fluids, they have to return to the hospital so they can be supervised to eat correctly and regain the proper fluid balance. This ends up costing the economy billions of dollars unnecessarily.  He concludes, “Perhaps people just need to follow instructions, but it’s possible with better monitoring that the situation can be improved.”

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

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

Get more information on applied environmental research in our

Environmental Biophysics: Top Five Blog Posts in 2015

In case you missed our best blogs, below are the five most-viewed Environmental Biophysics posts in 2015.


Sunflower field in Hokkaido

Do the Standards for Field Capacity and Permanent Wilting Point Need to Be Reexamined?

We asked scientist, Dr. Gaylon S. Campbell, which scientific idea he thinks impedes scientific progress.  Here’s what he had to say.



Environmental Biophysics Lectures

During a recent semester at Washington State University, a film crew recorded all of the lectures given in the Environmental Biophysics course. The videos from each Environmental Biophysics lecture are posted here for your viewing and educational pleasure.



Sensor Data Improves Cherry Production

Dr. Khot and his postdoc, Dr. Jianfeng Zhou, are using leaf wetness sensors to determine if and how long water is present on cherry tree canopies after a rain event. Dr. Khot hopes that data from these sensors will help growers decide whether or not it makes sense to fly helicopters in order to dry the canopies.


Maple leaf

What is the Future of Sensor Technology?

Dr. John Selker, hydrologist at Oregon State University and one of the scientists behind the Trans African Hydro and Meteorological Observatory (TAHMO) project, gives his perspective on the future of sensor technology.



Sensors Validate California Groundwater Resource Management Techniques

Michelle Newcomer, a PhD candidate at UC Berkeley, (previously at San Francisco State University), recently published research using rain gauges, soil moisture, and water potential sensors to determine if low impact design (LID) structures such as rain gardens and infiltration trenches are an effective means of infiltrating and storing rainwater in dry climates instead of letting it run off into the ocean.


Looking up at a tree canopy

Get more information on applied environmental research in our

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

Measuring Water Potential in Concrete

Trevor Dragon, a former METER Research and Development Engineer, was pouring concrete at his Beeville, Texas, farm one day and wondered if he could measure moisture in concrete with a matric potential sensor instead of the more traditionally used volumetric water content sensor (VWC) to get more accurate readings.  Dragon says, “We had about five concrete trucks come in that day, and we poured five different slabs.  Every truck had a different amount of water added.  One particular batch of concrete was really wet and soupy, and I became curious to measure it and compare it to the other slabs.”

Concrete slab drying down at Trevor's Texas farm.

Concrete slab drying down at Trevor’s Texas farm.

Why Measure Moisture in Concrete?

As concrete hardens, portland cement reacts with water to form new bonds between the components of the concrete.  This chemical process, known as hydration, gives concrete its characteristic rock-like structure.  Too much or too little water can reduce the strength of the concrete.  Adding excess water can lead to excessive voids in concrete while providing too little water can inhibit the cement hydration reaction. Thus, when you pour a slab in south Texas, where it’s exposed to high wind and intense heat, sufficient water must be added, and precautions must be taken to minimize evaporation of water from the slab surface as the concrete hardens.

Better Readings:

Dragon chose the matric potential sensor because he wondered if it would be more accurate than a VWC measurement.  He says, “I knew that VWC sensors were calibrated for soil, and because of that they would lack accuracy.  But the water potential sensor is calibrated for the ceramic it contains.  I figured it would be closer to the real thing without having to do a custom calibration.”

Moisture in concrete has been difficult to measure because the high electrical conductivity early in the hydration process throws off water content sensor calibration. So, Dragon was surprised when his data turned out to be really good.  He comments, “The dry down curve of the matric potential sensor was a perfect curve. There was a nice knee (drop from saturation) after about 200 minutes, and it just went down from there.  We’re kind of stumped because we are trying to understand why the data came out so well and why the curve looks so good.”  

MPS2 Water Potential in Concrete

Water Potential in Concrete

The scientists at METER sent the drydown curve to Dr. Spencer Guthrie, a civil engineering professor, to see what he thought.  He explains, “I suspect that the concrete is experiencing initial set at around 200 minutes.  This is a very normal time frame by which finishing operations need to be complete.  At this stage in cement hydration, the concrete becomes no longer moldable.  A rigid capillary structure is forming, and individual pores are taking shape.  As hydration continues, the pores become smaller and smaller, which may explain the decrease in matric potential.”

New Methods:

One theory Dragon and his colleague Dr. Colin Campbell came up with was that perhaps Dragon’s unique method of inserting the sensors made a difference in the measurements.  He explains, “The first thing I did was look for the rebar in the concrete, and I placed the sensors in the exact center of one of the squares to avoid the influence of metal on the sensor electromagnetic field.  Also, I didn’t insert the sensors the same way you would insert them into soil.  In soil, you put the sensors in vertically; I placed the water potential sensor horizontally because in this case, I was not interested in how water was moving in the slab but how it was being used over time.

What Does It Mean for the Future?

The behavior of the water potential sensor embedded in the concrete clearly indicated a drying process where water becomes less available over time. However, the implications are still unknown.  Can the quality of the concrete be determined from the speed or extent of water becoming less available?  Hopefully, this opportunistic experiment by Dragon will lead to more tests to show whether this approach is useful to others.  

Dr. Guthrie agrees the idea should be explored further and comments, “The matric potential measurements were not redundant with the water content measurements.  Instead, they offered additional, interesting information about the early hydration characteristics of the concrete.  In the context of construction operations, the water potential data indicated what is normally determined by observing the impression left in the concrete surface from the touch of a finger.  In the context of research, however, the use of a water potential sensor may yield helpful information about how certain admixtures, for example, influence the development of hydration products in concrete over time.

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

The Potential of Drones in Research

Someday soon,  multi-rotors will execute pre-programmed flight paths over several hundred research plots collecting daily data and sending it back to a computer while researchers sip their morning coffee.  Researchers and growers won’t need to know anything about flying: the drones will fly themselves.  This is the dream.

One UAV (unmanned air vehicle) industry leader at the above drone demonstration commented, The truth is that this is where agriculture (and research) is going, and I don’t mean ‘Tomorrowland’ going–I mean it’s pretty much there.  The only thing that’s holding us back is a permit from the FAA for autonomy, and that’s because the FAA is slowly backing into this UAV piece because we have the busiest general aviation sky in the world. But really, what you should have in your mind is multiple units operating with a single operator in a control vehicle.”  The above UAV was extensively tested in California’s NAPA valley with results soon to be published online.

In this blog, a METER scientist and an instrumentation engineer give their perspectives on what needs to happen before drones reach their full research potential.  


Drone Hexacopter

What are the advantages of drones for researchers?

Dr. Colin Campbell, research scientist-

One of the biggest challenges of work in the field is variability: low spots, high spots, sandy soil, clay soil, hard pans beneath the surface in some areas and not in others.  This results in highly variable performance in crops.  In addition to that, even when you have good homogeneity in a field, you might have differences due to irrigation or rainfall. If we want to improve agriculture, one thing that we have to do is be able to come out with better tools to be able to visualize the field in more than a single dimension. In order to do this right now, students go out and take plant measurements all day, every day, all summer long. The advantage of a drone is that you could do flyovers of a field, monitoring the traits that you’re interested in using reflectance indices that would normally take days of work.

What are the obstacles to progress?

Greg Kelley, mechanical engineer, and drone hobbyist-   

Recently, the FAA has come out with a set of guidelines for the industrial use of drones:  flying machines have to stay under a certain ceiling (500 ft; 150 m), and they have to be flown in the line of sight of the operator.  The naive thing about those policies is: how much control does the operator have over the drone anyway?  It used to be that with your remote control, you were moving the control surfaces (flaps, rudder, etc) on the aircraft, but this is changing.  The onboard computer performs things like holding a stable altitude, maintaining a GPS location, or auto-stabilization (it keeps the aircraft level, even when a gust of wind comes).  Those are degrees of control that have been taken away from the operator. Thus, according to the level of automation that the operator has built into the system, he may not be in direct control at all times. In fact, these machines are being developed so that they can fly themselves. From my perspective, the FAA regulations are going to have to evolve along with the automation of drones in order to allow the development of this technology in an appropriate way.


Drone with eight rotors.

What needs to happen before drones reach their full potential?

Dr. Colin Campbell–  

Even if we get the flexibility required with drones, we’ve got to get the right sensor on the drone. On the surface, this seems relatively simple.  Sensors to measure spectral reflectance are available in a package size that should easily mount on a drone platform. But, there are still many challenges.  First, current spectral reflectance sensors make a passive reflectance measurement, meaning we’re at the mercy of the reflected sunlight.  Clouds, sun angle, and leaf orientation, among other things, will all affect the measurement. There are several groups working on this (just search “drone NDVI” on the internet), but it’s a difficult problem to solve.  Second, drones create a spectral reflectance “map” of a field that needs to be geo-referenced to features on the ground to match measurements with position.  Once data are collected, the behavior of “plot A” can only be determined by matching the location and spectral reflectance of “plot A.”  Different from the first challenge, this is more related to programming than science but is still a major hurdle.

Despite these challenges, drones promise incredible benefits as an agricultural and environmental measurement tool. As one industry leader at the drone demonstration put it, “the complexity of the problems that agriculture faces and the opportunities for efficiencies are vast.  It will require ongoing engagement, next year and the year after that. There are a lot of questions to be answered and the efficacy is yet to be determined, but it’s exciting to watch the UAV helicopter and where it’s going.”  Both Campbell and Kelley agree that significant advances will be made within the next few years.

Read about an ROI calculator that’s been created to help growers quantify whether the benefits of using a drone will exceed their costs.

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

Get more information on applied environmental research in our

Great Science Reads: What our Scientists are Reading

We asked our scientists to share the great science reads they’ve perused recently.  Here’s what they’ve been reading:

great science reads

Letters to a Young Scientist by E.O. Wilson

great science reads

Steve Garrity: E.O. Wilson is a leader in the science of biology. This book is a simple read. What I like most about it is that it very effectively conveys Dr. Wilson’s passion for science. His thoughts on what it takes to be a successful scientist resonated with me the most.  In describing what it takes to be a successful scientist, E.O. Wilson says that being a genius, having a high IQ, and possessing mathematical fluency are all not enough. Instead, he says that success comes from hard work and finding joy in the processes of discovery. Dr. Wilson gets specific and says that the real key to success is the ability to rapidly perform numerous experiments. “Disturb nature,” he says, “and see if she reveals a secret.” Often she doesn’t, but performing rapid, and often sloppy, experiments increases the odds of discovering something new.

Out of the Scientist’s Garden by Richard Stirzaker

great science reads

Lauren Crawford: “Richard Stirzaker is a scientist out of Australia committed to finding tools to make farming easier and more productive in third world countries.  I love how he talks about what happens when he uses water from his washing machine on his garden and the unanticipated effects: what does the detergent do to the fertilizers and the soil properties?  It’s a scientific view of how a garden works.”

Introduction to Water in California by David Carle

great science reads

Chris Lund: “This is a great introduction to California’s water resources, from where the water comes from to how it is used….particularly relevant today given California’s ongoing drought and the hard choices California faces as a result.”

The Drunkard’s Walk:  How Randomness Rules our Lives, by Leonard Mlodinow

great science reads

Paolo Castiglione:  “The Drunkard’s Walk’s beginning quote perfectly reflects the author’s thesis: “In God we trust. All others bring data!”. I enjoyed the author’s discussion on how the past century was strongly influenced by ideologies, in contrast to the present one, where data seems to shape people’s actions and beliefs.”

Chapter 13 of An Introduction to Environmental Biophysics, by Gaylon Campbell

great science reads

Colin Campbell:  “Because of teaching Environmental Biophysics class, all my focus has been on reading An Introduction to Environmental Biophysics.  And, although I’ve read it too many times to count, I finally had a chance to study the human energy balance chapter (13) in depth, which was amazing.  The way humans interact with our environment is something we deal with at every moment of every day; often not giving it much thought. In this chapter, we are reminded of the people of Tierra del Fuego (Fuegians) who were able to survive in an environment where temperatures approached 0 C daily, wearing no more than a loincloth. Using the principles of environmental biophysics and the equations developed in the chapter, we concluded that the Fuegian metabolic rate had to continuously run near the maximum of a typical human today. The food requirements to maintain that metabolic rate would be somewhere between the equivalent of 17 and 30 hamburgers per day (their diet was high in seal fat).  You can read more about the Fuegians here.”

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

Get more information on applied environmental research in our

A History of Thermocouple Psychrometry

Dr. Gaylon S. Campbell gives a short history on his involvement in the development of thermocouple psychrometry:

thermocouple psychrometry

A psychrometer measures wet and dry bulb temperatures of air in order to determine the relative humidity or vapor pressure.

The Original Psychrometers:

I started working with psychrometers in Sterling Taylor’s lab when I was a sophomore at Utah State University in 1960.  A psychrometer measures wet and dry bulb temperatures of air in order to determine the relative humidity or vapor pressure.  In a conventional psychrometer, a thermometer bulb is covered with a wet wick and measured to find the wet bulb temperature.  A thermocouple psychrometer is used to measure the wet bulb temperature of air equilibrated with soil or plant samples. When a plant is at permanent wilting point, its relative humidity is close to 99%, so the whole range of interest for soil and plant measurements is between 99 and 100% RH. The measurements need to be very precise.  To make a wet bulb we couldn’t use a wick. We made thermocouples from 0.001” chromel and constantan wires. We cooled the measuring junction of the wires by running a current through it (cooling using the Peltier effect), condensed dew on the wires through the cooling, and then read the wet bulb temperature by measuring the thermocouple output as the water evaporated.  We needed to measure temperature with a precision of about 0.001 C.

thermocouple psychrometry

Diagram of isopiestic psychrometer used to measure the water potential of plant tissue. Image:

A New Idea:

The original psychrometers we used in Dr. Taylor’s lab were single junctions mounted in rubber stoppers and placed in test tubes in a constant temperature bath. They were calibrated with salt solutions.  Typically, before we could finish a calibration, we would break the thermocouple, so we never got data on soils. I found that frustrating, so had the idea of putting the thermocouple in a sample changer which would hold 6 samples. The sample changer went in the constant temperature bath. When it was equilibrated, we could make 6 readings without taking it out or opening it up. Calibration was done in one try, and we could start running soil or plant samples right away. This was a huge improvement. Our lab was one of a very few who could even make those measurements, and we could make them six at a time. That was about 1964.

Two New Businesses Born:

Later, when I was a graduate student at WSU, I started building soil psychrometers for my own research.  Other researchers wanted them, so I taught Marv Sherman, a vet student friend to do the manufacturing, and we sold the psychrometers to whoever wanted them for the cost of his time plus materials.  There was a sizable and growing demand when he and I graduated, and no one to carry on.  My brother Eric came for my graduation.  We asked him if he would like to take over the psychrometer business, and he said yes.  We sent him home with some instructions and the materials we had left from Marv’s work.  Eric built the business himself and then sold it to Wescor, where he and my brother, Evan became employees.  I contributed ideas and helped Wescor grow for a few years, but Eric and Evan were not satisfied there and wanted to start a business of their own.  We came up with the idea of them building a laser anemometer, and that was the start of Campbell Scientific.

thermocouple psychrometry

Decagon’s retired SC10/NT3 thermocouple psychrometer

More Improvements:

When we were on sabbatical in England in 1977-78 I had access to a small machine shop and a machinist who was willing to make things for me.  The sample changer psychrometers up to this time all had to be used in carefully controlled constant temperature water baths.  However, the soil psychrometers that my brother, Eric, sold at Wescor worked fine with no temperature control.  I suspected it would be possible to make a sample changer that didn’t need a constant temperature bath.  I made some sketches and the machinist made it for me.  It had places for 10 samples, had a large aluminum block to hold the rotor with the samples and the thermocouple, and stood on 3 legs.  It worked fine without any temperature control.

I showed the new sample changer to my brothers at Campbell Scientific, and they set up and machined a couple of them.  CSI didn’t have much interest in selling psychrometers, though, so Decagon began as a way for my children to earn money for college by selling the thermocouple psychrometer sample changer.  The name Decagon came both from the 10 people in our family when we started and the 10 samples in the sample changer.

Thermocouple Psychrometry Fades into History:

Decagon (now METER) began selling the thermocouple psychrometer system in 1982 and updated the user-intensive calibration and measurement system to a much simpler one in the mid-1990s.  Automation, speed, simplicity, and accuracy soon tipped the scales in favor of a dewpoint technique for measuring water potential, and the system was retired and replaced by a chilled mirror hygrometer (WP4C) in 2000.  However, Dr. Campbell believes that thermocouple psychrometers may still have a role to play in measuring water potential. If you’re interested in water potential, check out our water potential pages. It puts many of our best water potential resources in one place and contains sections on theory, measurement methods, and history.

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Founders of Environmental Biophysics Series: Sterling Taylor

Gaylon Campbell’s first experience with environmental measurement came in the lab of Dr. Sterling Taylor at Utah State University, where he was asked to make water potential measurements in order to understand plant water status. What he learned with Dr. Taylor became the start of four scientific companies and gave Dr. Campbell the tools and the confidence to become one of the world’s foremost authorities on physical measurements in the soil-plant-atmosphere continuum.  Here’s what Dr. Campbell had to say about his association with Dr. Taylor:

Sterling Taylor 1918-1967 Image: dlscience

Sterling Taylor 1918-1967 Image: dlscience

Who was Sterling Taylor and why is he considered one of the Founders of Environmental Biophysics?

Sterling Taylor was professor of Soil Physics at Utah State University.  He did his undergraduate work at what was Utah State Agricultural College, and earned his PhD at Cornell University. He worked on both theoretical and practical problems in soil physics.  His practical work focused on research in the area of plant-water relations and irrigation management.   Dr. Taylor worked out water potential limits for both maximum and reduced growth rates of crops. The irrigation limits tables that he put together are still used in today’s handbooks.  His theoretical contributions were on linked transport and applications of non-equilibrium thermodynamics to soil physics, which he was working on at the time of his death.   Dr. W. H. Gardner, a soil physicist of the time, called the amount of work Dr. Taylor and his students did “unparalleled” and noted that attendees at regional conferences often had to carry Taylor’s “weighty reports” home as overweight baggage.

Sterling Taylor

Attendees at regional conferences often had to carry Taylor’s “weighty reports” home as overweight baggage.

What was your association with him, and how did he influence your life and your science?

Sterling was a kind of second father to me and to many other young scientists.   He loved to help boys and teach them what their potential was.  At that age, I didn’t have any idea that I could do anything in science. The first assignment he gave me was to set up an experiment to measure the simultaneous movement of salt and water in soil.  I had no idea what I was doing, and it was a challenging project.  It would be challenging for me to do it right now!  But he’d give me ideas about how to do the next thing, I’d try to do it, and eventually I got some data that he thought was useful.  He did some analysis of it, and that’s how I learned to measure electrical conductivity and salt concentration in water and soil.  Sterling’s lab is also where my brother Eric and I learned how to make thermocouple psychrometers and other instruments for environmental measurements.  Those insights led directly to the start of Wescor and Decagon.  Campbell Scientific, Juniper systems and others eventually came from those beginnings.

Dr. Taylor was also a very patient man. He made a precision constant temperature bath out of an old washing machine.  It had an agitator in the middle to stir the water while cooling it with coils around the outside of the tub.  It was a wonderful setup, and he took a lot of pride in how well it worked.  He came into the lab one day while I was making some modifications to it.  I was drilling a hole through the outer jacket around the Freon(™) coils where the refrigerant ran.  He said, “Now be careful if you’re drilling holes through that thing so you don’t hit the coils”.  And I said, “Yes, I’m being careful.”  But I wasn’t.  The coils were a couple of inches apart, and I thought, There’s no way I’m going to hit one.  I didn’t even get a ruler.  I just eyeballed it, drilled a hole, and hit the tube dead on.  I couldn’t have hit it more perfectly if I’d measured as carefully as I could. All the refrigerant came hissing out, and I thought he would hear it over in his office.   He probably did hear it, but he didn’t come out to see what was going on.  One of the hardest things I ever did in my life was to go in and tell him I’d drilled a hole in his refrigerant tube.  He just said, “Well…I guess we’ll have to get some new refrigerant.”  He was just patient, and knew how to work with young people.

Sterling Taylor

I made a career choice to be a teacher and have students.

But that wasn’t the only way he influenced me.  As it came time for graduation he gave me some advice that had an enormous impact.  Once when I was trying to choose between soil physics and medical biophysics he said “do you want to be a little duck in a big puddle or a big duck in a little puddle?”  I decided on the little puddle.  On another occasion, I was wondering what kind of soil physics position would be best.  One of his former students had gotten a job at an experiment station near Kimberly, Idaho, and I thought that would be ideal.  He observed, “Those can be fun jobs, but if you go to a position like that you just don’t have any offspring.”  That resonated with me, and I thought, “I would like to have offspring.”  So I made a career choice to be a teacher and have students.  It was wonderful to have had that kind of advice at that critical time.

What do you think we missed because he died so early?

It’s interesting to think about scientific contributions and other types of contributions people make.  One of my sons gave me a book of science cartoons, and one of those cartoons shows a couple of scientists talking together. One of the scientists says to the other, “Isn’t it sad to think that everything we come up with now will be disproved in 20 years?”

It just shows you what a transient thing our work is. We think it’s so important, but the important contributions that Sterling made were the numbers of people that he influenced so profoundly.  I’m not the only one he was a second father to.  Sterling Taylor had a huge family of students.  Many went on to prestigious institutions like CalTech (California Institute of Technology), making important contributions over their careers.  And they trace it back to Sterling’s influence on them.

How can scientists today emulate the great man that he was?

I think it would be to not take science so seriously but to take interactions with their fellow travelers seriously. There is a quote by Clayton Christensen from an article in Harvard Business Review on how to emulate what Sterling Taylor was. Christensen says, “I’ve concluded that the metric by which God will assess my life isn’t dollars but the individual people whose lives I’ve touched.  I think that’s the way it will work for us all. Don’t worry about the level of individual prominence you have achieved; worry about the individuals you have helped become better people. This is my final recommendation: Think about the metric by which your life will be judged, and make a resolution to live every day so that in the end, your life will be judged a success.”

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4 Funding Tips from an Experienced Grant Writer

Dr. Richard Gill developed an interest in ecology as a child while exploring the forests and seashores of Washington State. This attraction to wild places motivated Dr. Gill to study Conservation Biology as an undergraduate at Brigham Young University and to receive a PhD in Ecology from Colorado State University.


Dr. Richard Gill, ecologist at BYU

His PhD research on plant-soil interactions in dryland ecosystems, supervised by Indy Burke, dovetailed well with his postdoctoral research on plant physiological ecology with Rob Jackson at Duke University. Dr. Gill returned home to Washington in his first faculty position at Washington State University. There he pursued research on global change ecology, studying the impacts of changes in atmospheric CO2, temperature, and drought. In 2008 he joined the faculty of Brigham Young University as an associate professor of biology. He teaches Conservation Biology courses and in the general and honors education curriculum.

Dr. Gill has been successful in obtaining funding from the National Science Foundation, the U.S. Department of Agriculture, U.S. Dept of Energy, and the U.S. Department of the Interior.  He also helped guide one of his graduate students in winning research instrumentation from the Grant Harris Fellowship, provided by METER.  We interviewed him about his thoughts on successful grant writing.  Here’s what he had to say:

  1. Understand the call: I think it’s important to understand what’s being asked of you and write to the call for proposals itself.  We all have ideas, and we think everybody should give us money for every idea that we have.  That’s part of being a scientist, but understanding the parameters and the purpose of the grant is crucial.  This is because the easiest way to eliminate proposals is to cull those that don’t address the call.  In this way, proposal readers go from a stack of 200 to a stack of 50, without having to get into the details of the research at all.  So my advice is to read the call for proposals, and make sure you actually address what they ask for and stick to the requirements for length and format.
  2. Be true to the vision: There is always some sort of vision tied to the call, so make sure you are true to that vision.  For example, let’s say it’s the Grant Harris Fellowship, which provides instrumentation for early career students to do something they wouldn’t otherwise be able to do.  Make sure you say, “Here’s what I’m already doing with the funding and instrumentation that we have in our lab.  There’s a key component missing, and I can only do it if you support me.”  Show a clear need, aligning your research with the purpose of the proposal, and you’ll have a strong case for funding.
  3. Make sure you edit: Many proposals don’t get funded because of poor writing.  Your great ideas can’t come forward if the reader is mired down in your verbiage.  Don’t send them your first draft.  Make sure you have somebody read it for clarity.
  4. Be clear and concise: When scientists are involved in a project, it is common to develop a sort of tunnel vision, a byproduct of having worked on the project for years and being familiar with all the details.  When you write a proposal you should remember that the person who is reading is going to be intelligent, but have no idea what you’ve been doing.  You should say, “Here’s what I’m going to study, why I’m going to study it, and how I’m going to test it.”  Be clear, specific, and declarative.

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