Skip to content

Posts from the ‘Uncategorized’ Category

Weather Data: Virtual, In-Field, or Regional Network—Does It Matter?

Which data source is better?

In the world of specialty crops, there is disagreement on how well weather-driven insect, disease, and frost prediction models actually perform. Dr. Dave Brown, former director of Washington State University’s AgWeatherNet spent years comparing different weather data sources and how those data affect the accuracy of common environmental models used by orchard growers. In this 20-minute webinar, he shares the surprising things he learned.

Decrease chances of crop damage with one simple practice

Find out how you can increase the accuracy of your predictive models and decrease frost, insect, and disease incidents by doing just one thing differently—improving the quality of your weather data. Discover:

  • Microclimates: what are the conditions like inside a crop canopy versus outside?
  • Virtual data vs. weather station data: Which is better?
  • How do site-specific weather data vs. regional network data compare?
  • How much does a small decrease in data quality affect the accuracy of your models?
  • What’s the value of in-orchard measurements?
  • What are some best practices for higher data quality?

Register now—>


For 20 years as a faculty member at Montana State University and Washington State University (WSU) Dr. Dave Brown pursued research on soil sensors, spatial data science, and digital agriculture. At both universities, he served in many leadership roles for major research projects, academic programs, and most recently as Director of the WSU AgWeatherNet program. In this capacity, Dr. Brown hired and supervised a team of meteorologists who pursued research and extension activities focused on evaluating and improving the quality of weather data used for agricultural decisions.

Just Released—New Environmental Measurement Podcast

Check out a new podcast made by contributors to the blog. We Measure the World is a podcast produced by scientists, for scientists. Application expert Holly Lane and data guru, Brad Newbold interview scientists from all types of disciplines who measure anything and everything about the world to make it better—and more sustainable.

Holly Lane interviews scientists from all types of disciplines

Hang with us to learn a lot and laugh a lot. Explore interesting environmental research trends, how scientists are solving research issues, and what tools are helping them better understand measurements across the entire soil-plant-atmosphere continuum.

Listen now—>

The researcher’s complete guide to NDVI and PRI

NDVI and PRI: theory, methods, and application

Modern technology makes it possible to sample spectral vegetation indices such as NDVI and PRI across a range of scales both in space and in time, from satellites sampling the entire earth’s surface to handheld small sensors that measure individual plants or even leaves.

Figure 1: NDVI is sensitive to the amount of vegetation cover that is present across the earth’s surface (source: low res map obtained from an earth orbiting satellite)

What are NDVI and PRI?

NDVI and PRI are both spectral vegetation indices derived from measurements of relatively narrow wavelengths of reflected light (10 to 50 nanometers) in the electromagnetic spectrum. This is useful for measuring various properties in plant canopies. NDVI stands for the Normalized Difference Vegetation Index and PRI stands for the Photochemical Reflectance Index.

image of SRS spectral reflectance sensor to measure NDVI and PRI | METER Environment
The METER SRS sensor measures both NDVI and PRI and works with ZENTRA Cloud for data visualization in near-real time.

There are many types of spectral vegetation indices, however, this article and the webinar below focus on the theory, methods and application of NDVI and PRI as they are two of the most commonly used (see webinar).


NDVI is especially useful for measuring plant canopy structural properties such as leaf area index, light interception and even biomass and growth, whereas PRI is more useful for getting at functional properties of plant canopies such as light use efficiency. Recent literature shows that PRI is also useful for measuring foliar pigments.

Understanding canopy radiation interactions 

To understand where NDVI and PRI come from, it’s important to learn about canopy-radiation interactions. There are three primary fates for electromagnetic radiation as it interacts with plant canopies.

Read more—>

Water content + water potential—better together

New soil moisture master class

Everybody measures soil water content because it’s easy. But if you’re only measuring water content, you may be blind to what your plants are really experiencing. To understand when to water or plant water stress, you need to measure both water content AND water potential.

Learn more in our soil moisture master class, “Secrets of water in soil“. 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.

View master class—>

How to install soil moisture sensors—faster, better, and for higher accuracy

Why installation is everything

If you want accurate data, correct sensor installation should be your number one priority. When measuring in soil, natural variations in density may result in accuracy loss of 2 to 3%, but poor installation can potentially cause accuracy loss of greater than 10%. 

Image of a researcher holding a TEROS-12 soil moisture sensor
TEROS 12 soil moisture sensor

Proper sensor installation is the foundation for the data you collect. If you have a poor foundation, it makes data interpretation difficult. In this article, get insider tips on how to install soil moisture sensors faster, better, and for higher accuracy.  Learn:

  • What to be aware of when installing sensors
  • What installation trouble looks like in your data
  • Installation priorities for soil moisture sensors
  • How METER is advancing the science of installation for higher quality data

Understand your sensors

To understand why poor sensor installation has an enormous impact on the quality of your data, you’ll need to understand how soil moisture sensors work. 

Soil moisture sensors (water content sensors) measure volumetric water content. Volumetric water content (VWC) is the volume of water divided by the volume of soil (Equation 1) which gives the percentage of water in a soil sample.

Image of the equation used to calculate the measure of volumetric water content
Equation 1

So, for instance, if a volume of soil (Figure 1) was made up of the following constituents: 50% soil minerals, 35% water, and 15% air, that soil would have a 35% volumetric water content.

Image of a diagram showing soil constituents in a volume of soil
Figure 1. Soil constituents

Why capacitance sensors work

All METER soil moisture sensors use an indirect method called capacitance technology to measure VWC. “Indirect” means a parameter related to VWC is measured, and a calibration is used to convert that amount to VWC. In simple terms, capacitance technology uses two metal electrodes (probes or needles) to measure the charge-storing capacity (or apparent dielectric permittivity) of whatever is between them.

Image of a diagram depicting how capacitance sensors use two probes to form an electromagnetic field
Figure 2. Capacitance sensors use two probes (one with a positive charge and one with a negative charge) to form an electromagnetic field. This allows them to measure the charge-storing capacity of the material between the probes.

Read more—>

Weather Monitoring 101: Which Weather Station is Right for You?

Choosing the right weather station can be confusing. Hundreds of options exist for weather monitoring ranging from $200,000+ aviation-grade observation systems to $25,000 WMO-grade mesonet stations with redundant rain gauges and multi-height wind and temperature observations, all the way to $300 hobbyist-level stations.

Researcher setting up an ATMOS 41 all-in-one weather station
ATMOS 41 all-in-one weather station

How do you know which system is right for you? And what is the sweet spot for price vs. maintenance vs. accuracy for your unique application?

Understand your choices

  • Why you need weather data as an ancillary measurement, even if your primary measurement needs are in the soil or plant community
  • Why you should consider data quality vs. maintenance and measurement parameter combinations in your cost analysis
  • 3-season vs. 4-season performance 
  • Which situations require low-, medium-, or high-grade solutions, and how high should you go?
  • Pros and cons of different solutions
  • Where is the sweet spot for performance divided by price in your application?

In this 40-minute webinar, METER research scientist, Dr. Doug Cobos explores the research weather station price vs. utility continuum. Find out:

Watch the webinar—>


Dr. Cobos is a Research Scientist and the Director of Research and Development at METER.  He also holds an adjunct appointment in the Department of Crop and Soil Sciences at Washington State University where he co-teaches Environmental Biophysics.  Doug’s Masters Degree from Texas A&M and Ph.D. from the University of Minnesota focused on field-scale fluxes of CO2 and mercury, respectively.  Doug was hired at METER to be the Lead Engineer in charge of designing the Thermal and Electrical Conductivity Probe (TECP) that flew to Mars aboard NASA’s 2008 Phoenix Scout Lander.  His current research is centered on instrumentation development for soil and plant sciences.

Watch it now

Read more about which remote weather station is right for you.

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

Image of a researcher running hand across wheat

Researcher Running A Hand Across Wheat

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

Image of a fallen tree being supported off the ground by many other trees

A Forest With Fallen Trees

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

Image of a researcher collecting information from a ZL6 data logger

Researcher is Collecting Data from the ZL6 Data Logger

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

Image of rolling hills of farm land

Rolling Hills of Farm Land

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.

Image of a researcher measuring with the HYPROP balance

Researcher measuring with the HYPROP balance

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

Image of a researcher holding a TEROS 12 in front of a field

Modern Sensing is more than just a Sensor

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

Image of a dirt plowed field being used for electrical conductivity

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

Image of a crop field


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?

Image of plants growing out of the sand

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—>

Image of grapes growing off of a tree

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

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.”

Green wheat stalks

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.”

Boy walking through a library

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.  

Researcher looking through a microscope

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.

Patients had wrapped in gauze with a tube

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.”

Stuart Campbell operating on the heart for a medical procedure

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?”  

Nurse measuring heart rate

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.

Sunflowers in a sunflower field

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.

Pine tree branch


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.

Cherries on a cherry tree


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 leafs on a maple tree

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.

Wet rocks on a riverbank with water flowing down through


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

Looking up at a tree canopy

Get more information on applied environmental research in our

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