Posts tagged ‘Soils’

Mar 23

What Does SMAP Mean for In Situ Soil Water Content Measurement?

With the recent news coverage of the SMAP (Soil Moisture Active Passive) satellite launch, researchers may wonder: what does remote sensing mean for the future of in situ measurements? We asked two scientists, Drs. Colin Campbell and Chris Lund, for answers to this complex question. Here’s what they had to say:

Image: www.jpl.nasa.gov

What is SMAP?

SMAP is an orbiting earth observatory that estimates soil moisture content in the top 5 cm of soil over the entire earth. The mission is three years long with measurements taken every 2-3 days. This will allow seasonal changes around the world to be observed over time, improving our ability to manage water resources and better parameterize land surface models. SMAP determines the amount of water found between the minerals, rocky material, and organic particles found in soil by measuring the ability of radar to penetrate the soil. The wetter the soil is, the less the radar will penetrate. SMAP has two different sensors on the platform: an L band aperture radar with a resolution of about a kilometer when it’s looking straight down (the pixel size is about 1 km by 1 km), combined with a passive radiometer with about 40 km of resolution. This combination creates a synthetic product that takes advantage of the sensitivity of the radiometer.

What does SMAP mean for in situ soil water content measurement?

It’s all about scale: In some ways, comparing in situ to SMAP measurements is like comparing apples to…well…mountain-sized apples. The two forms of measurement use vastly different scales. In situ soil moisture sensors measure water content at the volume of several liters of soil, maximum. Even the sensor with the largest field of sensitivity, the neutron probe, can only integrate a volleyball-sized volume. On the other hand, SMAP measures at a resolution of 1 km2, which is larger than the size of a quarter section, a large field for many farmers. Global soil moisture maps will allow scientists using SMAP to look at big picture applications like weather, climate and hydrological forecasting, drought, and flooding, while more detailed in situ measurements will tell a farmer when it’s time to water, or help researchers discover exactly why plants are growing in one location versus another. The difference in spatial scale makes the two forms of measurement useful for very different research purposes and applications. However, there are applications where the two measurements can be complementary. Most notably, in situ measurements are often temporally rich while being spatially poor. But, SMAP can be used to scale in situ measurements to areas where in situ measurements are absent. In situ measurements can also be used as a source of validation data for SMAP-derived values for any location where both in situ and SMAP measurements overlap. Thus, there is opportunity for synergy when pairing SMAP and in situ measurements.

Satellite image in Winter.

What can SMAP do that in situ measurement can’t?

Scientists say they’ve seen a relationship between the top 5 cm of soil moisture and some factors related to climate change and weather. Because in situ soil sensors sample across a spatial footprint of a few meters, it can be very difficult to use their data to say anything about processes occurring across broad spatial scales; two liters of soil is not going to tell you anything about weather or flooding. SMAP can help us better understand the interaction between the land surface and atmosphere, improving our understanding of the global water cycle as well as regional and global climate. This will help with forecasting crop yield, pest pressure, and disease…that’s big picture research.

The productivity of a forest also may depend on the general soil moisture measured by SMAP. For instance, if we got an idea of the soil moisture and greenness of a forest, we could tie together the approximate water availability and the resulting biomass accumulation with incoming solar radiation. Better biomass accumulation models could lead to better validation of global carbon cycle models.

SMAP will also be able to detect dry areas across the U.S. and challenges they might present. Surface runoff that leads to flooding could also be predicted as scientists will be able to see where soils reach saturated conditions.

In other applications, people working on global water or energy budgets have to parameterize the land surface in terms of how wet or dry it is. That’s the big advantage of SMAP’s relatively new data sets. Any time you’re running a regional climate model you have to parameterize what the soil moisture is in order to partition surface heat flux into sensible and latent heat flux. If there’s a lot of available water, it’s weighted more toward evaporation and less toward sensible heat flux. In areas where there’s little available water and low evaporation, you get high surface temperatures and sensible heat flux. So SMAP will be important for model parameterization as we haven’t had a good global data set for soil moisture until now.

In situ sensors show how much water is lost from the root zone and what is still left.

What can in situ sensors do that SMAP can’t?

In irrigated agriculture, farmers need to know when and how much to irrigate. In situ sensors give them this information by showing how much water was lost from the root zone and what is still left. SMAP is unable to tell you what’s down in the root zone; it only reaches to 5 cm. Additionally, 1 km resolution is larger than most irrigation blocks. These factors mean that it will be difficult to make irrigation decisions from SMAP alone.

Scientists using in situ sensors are concerned with the soil moisture available in a local area because their time resolution is excellent and they have the ability to resolve what’s happening in particular conditions related to crops or natural systems. Natural systems are often heterogeneous, meaning there may be adjacent areas with different types of vegetation including trees, shrubs, and grass. Tree roots may grow deep while grass roots are shallow. Being able to look over all these different areas without averaging them together, as SMAP does, is critical in some applications.

What about geotechnical applications? Literature suggests SMAP output can help predict landslides. It is more likely that it can only see when the soil is generally saturated and generate a warning. But in slopes that are at risk of landslides, in situ monitoring with sensors such as tensiometers to measure positive pore water pressure may be more useful for determining when a slide is imminent.

SMAP, like in situ water content measuring systems, is also limited by the fact that it measures the amount, not the availability, of water. If it measures 23% water content in a certain area, that measurement may not tell us what we want to know. A clay soil at 23% VWC will be close to wilting point while a sand would be above the plant optimal range. SMAP doesn’t measure the energy status of water (water potential), so even if SMAP tells us a field has water content, that water might not be readily available. Water availability must be determined through a pedo-transfer function or moisture release curve appropriate for a specific soil type (It is possible to overlay SMAP data on soil type data to estimate energy state, but this might not be fine enough resolution to be useful).

Complementary Technology

How do SMAP and in situ instruments work together? The key is ground truthing in situ soil moisture measurements with SMAP type satellites and vice versa. Ground-based measurements at specific locations can be matched with satellite information to extrapolate over a field and gain confidence in the small continuous scale alongside the larger infrequent scale. It’s analogous of a video camera recording one plant continuously while a single shot camera snaps whole-field pictures every day. With the SMAP “single-shot” we can say, something changed from time A to time B, but we don’t know what happened in the middle (rain event, etc.). In situ measurements will tell us the details of what happened in between each snapshot. Putting both data sets together and matching trends, we can show correlation and complete the soil moisture picture. Basically, In situ measurements provide temporally rich information about soil moisture from a postage stamp-sized area of earth’s surface (driven by highly localized conditions), whereas SMAP gives us the ability to monitor broad scale spatiotemporal patterns across all of earth’s surface (driven by synoptic conditions).

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Mar 16

The History and Future of Water Potential

I often hear researchers complain about the accuracy of our TEROS 21 water potential sensors. We still have room to improve, but we’ve certainly come a long way! People have been attempting to make water potential measurement in the field for over 100 years. The following is a brief overview of the evolution and history of water potential measurements over that time.

Pre-MPS-1 prototype.

Livingston Discs

The Livingston disc, developed in 1908, was one of the first attempts at determining water potential in the field. The Livingston Disc was actually a primitive, manual version of the technology used in our MPS6 ceramic disc. Here is how it worked: first, you’d weigh the dry disk, then put it in the soil and let it equilibrate. After that, you would dig it up and weigh it again. Using the water retention curve of the disc, you could then determine the water potential.

Gypsum block

In the 1940s gypsum block sensors were invented as the first solid matrix equilibrium technique for water potential. This method tried to continuously sense water potential with a simple electrical conductivity measurement in a solid porous (and naturally occurring) gypsum matrix. However, because naturally occurring gypsum doesn’t have a consistent pore size distribution and it degrades over time, the instrument was not very accurate.

In the 1940’s gypsum block sensors were invented as the first solid matrix equilibrium technique for water potential. Image: www.soilmoisture.com

Tensiometers

In the 1960’s a liquid equilibration technique called tensiometry was discovered that allowed water potential measurement with good accuracy even in the presence of positive pore water pressures. Tensiometers work extremely well in wetter soils with water potentials between 0 and -80 kPa and should be the choice for all wet soil applications, especially above -9 kPa where the MPS6 will not work (the air entry value for its ceramic is -9 kPa). However, when the soil dries out the water under tension in the tensiometer eventually cavitates, causing the output to be useless until they are refilled. Thus solid equilibrium techniques like the TEROS 21 are the best choice across the dry range.

Tensiometers are the most accurate way to measure water potential in the field in the wet range, but are limited to the plant optimal range of about -100 kPa and above.

The Evolution of Ceramic Discs

We learned with the gypsum blocks that one of the challenges in solid matrix water potential measurement is finding a material that will create the same water retention curve every time. In quest of this goal, the ceramic discs in sensors like the TEROS 21 have taken years of development. Because of the limited range of the tensiometer, we wanted to develop a water potential sensor that could measure over a larger range. The hardest part about developing that ceramic was getting a variety of pore sizes so the instrument could read said wide range of water potentials. This started years ago in the lab of Dr. Gaylon Campbell at Washington State University where his technician, Kees Calisendorf, experimented over a long period of time to come up with the perfect recipe.

The MPS1 was our original matric potential sensor released in 2001. It allowed for long-term monitoring in the field because, unlike gypsum, the ceramic did not degrade over time.

Even after we found a consistent ceramic, there were still outliers. So creating a calibration method was essential to making an accurate sensor. The first challenge was to be able to store calibration points in the sensor, which required a microprocessor. The second, and more difficult task, was to establish a method to calibrate large numbers of sensors at once. We tried many different approaches like pressure plate, equilibration over salt solutions, and even centrifugal force, but nothing worked. Finally, in a discussion with our partner, UMS, we discovered the key. We now can accurately calibrate 50 sensors at a time in only 12 hours. Still, even with these advanced techniques, we only have a sensor with an accuracy of plus or minus 10%, but considering the history of how hard it’s been to develop consistent ceramic, this accuracy is exciting for the range that we can get.

The MPS 2 was our second matric potential sensor which offered two-point calibration and a temperature sensor, improving accuracy.

What’s Next?

Now that we’ve created a reliable calibration method, we can turn our attention toward further improving the sensor measurement range as well as its accuracy. Testing different ceramics, or other porous media, may hold the key to a solid equilibrium technique sensor reading all the way to 0 kPa, eventually replacing the need for tensiometers in the field.

The two key innovations in the MPS6 (now called TEROS 21), released in 2014, are the addition of a microprocessor to the sensor and fast, accurate equilibration at multiple points.

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.

Watch it now—>

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Mar 9

Could This Farming Practice Make Food Grown in Fukushima Safe?

March 11, 2015 marks four years since the Fukushima disaster. What have we learned?

Shortly after the Fukushima disaster, we donated some of our sensors to Dr. Masaru Mizoguchi, a scientist colleague at the University of Tokyo. He is using the equipment to contrive a more environmentally friendly method to rid rice fields in the villages near Fukushima of the radioactive isotope cesium 137.

Over the last three years, government contractors removed 5 cm of topsoil from fields in order to extract the radioactive isotope. The topsoil has been replaced with sand. The problem with this method is that it also removes most of the essential soil material, leaving the fields a barren wasteland with little hope of recovery anytime soon. Topsoil removal may also prove ineffective because wild boars dig up the soil to root for insects and larvae. This presents a problem in the soil stripping method, as it becomes impossible to determine exactly where the 5 cm boundary exists. In addition, typhoons and heavy rains erode the sand surface raising safety and stability concerns.

Currently, bags full of radioactive topsoil are stacked into pyramids in abandoned fields. An outer black bag layer filled with clean sand is placed around the outside to prevent radiation leakage. The government has promised that these bags will be removed and taken to a repository near the destroyed reactor, but many people don’t believe that will happen as the bags themselves only have a projected life of 3-5 years before they start to degrade. More of these pyramids are being built around Iitate village every day, which is a source of uneasiness for many people that are already cautious about returning.

Dr. Mizoguchi and his colleagues have come up with a new “flooding” method now being tested in smaller fields that can save the topsoil and organic matter while at the same time removing the cesium, making the land usable again within two years. The new method floods the field and mixes the topsoil with water, leaving the clay particles suspended. Because the cesium binds with the clay, they can drain the water and clay mixture into a pre-dug pit and bury it with a meter of soil after the water has infiltrated. After one year of using this method, the scientists saw that the cesium levels in the rice had gone down 89%. And in situ and laboratory instrumentation have shown that two years after cesium removal, the plants’ cesium uptake is negligible, and the food harvested is safe for consumption.

Dr. Mizoguchi standing by a sensor station containing Decagon sensors

Dr. Mizoguchi is monitoring the surrounding forests with our canopy and soils instrumentation in order to determine if runoff from the wilderness areas will return cesium to the fields and what can be done about it. He’s figured out a way to network all the instrumentation and upload data directly to the cloud. Still, even if this technology and new methodology work, will people around the world ever feel safe eating food grown near Fukushima? Dr. Mizoguchi says, “I believe that the soil is recovered scientifically and technically. However, harmful rumors will remain in the public mind for a long time, even if we show the data that proves safety. So we must keep showing the facts on Fukushima based on scientific data.”

Resurrection of Fukushima Volunteers using Dr. Mizoguchi's method to rehabilitate small farms

Resurrection of Fukushima volunteers use Dr. Mizoguchi’s method to rehabilitate small farms

Incredibly, each weekend a volunteer organization of retired scientists and university professors use their own money and time to travel out to small village farms. There they labor to rehabilitate the land using Dr. Mizoguchi’s method. One of the recipients of this selfless work is a 72-year-old farmer who took his nonagenarian mother and returned to their home to fulfill her heartfelt plea that she could live out her final years outside the shadow of a highrise apartment (see this story in the video above). We are honored to be a part of this humanitarian effort.

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

Get more information on applied environmental research in our

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Mar 2

Water Content Innovation Involves Growing Pains

Months ago, I was reading about the tragic test-flight crash of the Virgin Galactic passenger rocket plane and noting that there was a lot of criticism of that company for it’s “risky space venture.” In the midst of the heartbreak I felt at the deaths of the two pilots, as an innovator, I can somewhat sympathize with the Virgin Galactic Company in the realization that historically, innovation has involved risk. If you think about airplane development in the early 1900’s, every year 20% of pilots died because of malfunctions on airplanes (“By the spring of 1917, the life expectancy of a British pilot was put at eight days.” Van Creveld, The Age of Airpower, p. 28). Today we worry about the safety of air travel much less because people were willing to go through years of painful learning, and because of that learning, we no longer use trains as our fastest transportation.

Thankfully, no one’s life is on the line with Decagon sensor innovation. However, similar to early airplanes and the new rocket plane, when we release an instrument that is completely new (like our circuit board water content sensors), there are occasional problems that are not accounted for in our extensive laboratory and field testing. In light of this, we are grateful for scientists who are willing to give us feedback in order to aid innovation and advancement of science and technology. Here is an example of how scientists became our collaborators in developing a new product that helped to advance their discipline.

In 2000 we made our first water content sensor where we put the circuit board on the sensor itself, rather than a data logger. In advance of its release, we made a version of the sensor that was flexible with the idea that it would have excellent contact by conforming to the soil. In theory, it looked great, but when it was put in the ground, the sensor flexed and popped the components off the circuit board. Thanks to testing feedback, we made more rigid, 20cm long sensors, and the components had no more trouble.

Greenhouse with Plants Hanging from the Roof

Researchers loved the instrument but wanted shorter ones to put in greenhouse pots.

After this problem was solved, researchers loved the instrument but wanted shorter ones to put in greenhouse pots. So we made the shorter ones. Scientists then became concerned that the sensors were sensitive to salinity in higher electrical conductivity conditions. Coincidentally, components became available to raise the frequency to 70 MHz, which is much less sensitive to electrical conductivity. Thus, because scientists were willing to partner in the development process and learn with us, we have developed a sensor that is affordable, cutting-edge technology which advanced the discipline of soil science.

We love to partner with scientists in the pursuit of knowledge. A researcher at a conference once said to one of our scientists, “I hate your stuff…for the first couple of months. But then you guys take your lumps, make it better, and then I buy all your stuff.” He was saying this in jest because it certainly doesn’t happen with many of the products we release. But when it does, we appreciate the dedicated support of our scientist friends who enjoy learning along with us to make the same kind of advancement that helped the world move from trains to air, and now onward into commercial space travel.

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Feb 17

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:

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.
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.
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.
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.

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

Get more information on applied environmental research in our

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Feb 11

1 Comment

Founders of Environmental Biophysics Series: John Monteith

We interviewed Gaylon Campbell, Ph.D. about his association with one of the fathers of environmental biophysics, John Monteith.

John Lennox Monteith, image:agrometeorology.org

Who was John Monteith?

John Monteith was a professor at the University of Nottingham in England and one of the founders of modern environmental biophysics. He pioneered the application of physical principles in the study of how plants and animals interact with their immediate environment. He started his career at Rothamsted Experimental Station in Harpenden, England and was hired as professor at Nottingham in the early 1970’s. He went on to spend time at the International Crops Research Institute for Semi-Arid Tropics (ICRISAT) in India. He published a textbook that has been a foundation for Environmental Biophysics, called Principles of Environmental Physics. He was elected a member of the Royal Society of London, which is the highest scientific distinction a person can receive in the UK. He was also a member of the Royal Meteorological Society and was its president in 1978. These societies are both sponsored by the crown, and he told me on the occasion that he was installed as the president of the Royal Meteorological Society, the queen attended and he sat by her at dinner. He is known for the Penman-Monteith equation that has become the basis for guidelines for estimating irrigation water requirements used by the FAO (Food and Agriculture Organization of the United Nations).

How did you meet him?

As an undergraduate, I knew of John because I worked for a professor at Utah State University (Sterling Taylor), who was measuring water potential in soil using thermocouple psychrometers. I was keenly interested in the subject, so Dr. Taylor gave me a paper on thermocouple psychrometers to read, published in 1958 by Monteith and Owen, written while John was at Rothamsted. John’s work there was influential in developing instrumentation which formed the foundation for Wescor, METER, and several other companies.

When Prof. Monteith’s book came out, it was pretty exciting for me, because it had everything in it that I was trying to teach as a professor of Soil Science. I wrote to John in 1977 inquiring about the possibility of doing a sabbatical there, and he wrote back immediately and arranged for us to come. Amazingly, he and his technician met our big family at Heathrow airport and loaded up the whole crew, including our many duffel bags, into a university minibus. A couple of our bags were missing, and John picked them up from the railway station in Nottingham and delivered them to us the next day. I have often marveled that such a busy and important man would take the time to care for us like that.

A sunflower field in Karnataka, India

What was he like as a colleague?

He was a humble man in a lot of ways. After he passed away, one of his colleagues wrote in and told about some of the experiences he’d had with John in India. India has a pretty hierarchical society, and it’s not uncommon for somebody who is in a position of authority to take advantage of that. John was in charge of one of the big groups within ICRISAT, and the thing that impressed his colleague was that whoever came into John’s office was treated with great respect, whether it was the cleaning person or the lab technician. If they had come to see him, they got the same treatment and the same respect that the director of the lab got.

We worked on a lot of projects together, but the proposal we submitted that was funded was one on improving thermocouple psychometry. I wrote up the paper, but he had written the proposal and provided the funding for the work. I put him down as an author on the paper, and when I got ready to submit it, he went over the paper just as if he were an author and then crossed his name out. He said he hadn’t contributed enough. Well, he contributed way more than most authors do, but he had a set of standards that he expected himself to meet and his contributions to that paper hadn’t met those standards. He was pretty amazing that way.

How did he get to be a part of the Penman-Monteith Equation?

Penman was head of the research group at Rothamsted Experimental Station which Monteith joined, following graduation. Penman was already an established researcher by the time Monteith got there, and the Penman equation was already well known. But, Monteith worked with that equation, and in my opinion, improved it substantially. He never wanted to take credit for that. He always claimed that Penman already understood the things he had added, and he never did call it a Penman-Monteith equation, always referring to it as the Penman equation. But I have never read things of Penman’s that indicated that he had anywhere near the depth of understanding of the equation that Monteith had. To my way of thinking, it’s completely appropriate that his name is associated with it.

What was John’s secret to accomplishing all he did, and how can scientists today emulate his meaningful career?

His gift was the gift of clear thinking. I gave a talk about him a while ago entitled “Try a Straight Line First.” John hated the complexity of modern computer models for crop growth because he couldn’t easily see the end from the beginning in those models. He had the ability to look at a problem, no matter how complex, and just reach in and grab the essence of that problem and show it to you. He used to talk about Occam’s Razor and not multiplying complexity. Einstein was supposed to have said, “Everything should be as simple as possible, but not simpler.” John was always able to find a simple way to look at problems. It may have been a complex process to get there, but once he was done, you had something that you could manipulate. I think simplicity and uncluttered thinking would be the thing to emulate.

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Feb 2

2 Comments

Learn to Measure Water Potential at a Bodentag

One of the best parts of my job is the opportunity I get to teach others about the science and technique of measurement. For more than 10 years, I have participated in seminars and workshops all over the world to do just that. But, a couple of months ago, I had my first opportunity to work with my good friend Georg von Unold (METER Ag) to do a Bodentag workshop, German-style. I learned a lot from my experience, and I think the participants did as well.

UMS’s Georg von Unold with his backhoe, digging a permanent soil observation pit in the Black Forest

A Bodentag (meaning “soil day” in German) is an unusual opportunity for the attendees to get practical hands-on teaching and training from the people who understand soil and environmental instrumentation. In a typical conference, you will not get a chance to do things under field conditions. Instead of sitting in a conference room all day, a Bodentag starts with presentations to set the stage with the theory and principles of measurement, but quickly moves to the lab and field to get the participant’s hands dirty. With the diversity of measurements required for today’s multidisciplinary research, there is great value in structured field installation familiarity.

Our trip to Freiburg was a great example of how a Bodentag works. Preparation started early in the morning the day before as Georg used his large Mercedes Sprinter van full of equipment to tow his Bobcat excavator for more than five hours on our drive from Munich. When we got there, we were directed to a nearby site in the Black Forest where we used the excavator to dig a permanent soil observation pit (Georg’s gift to the institute there), complete with a stairwell that allowed people to go and inspect the pit face and install sensors. We prepared other stations to get people to install soil sensors with minimum impact, cut out intact soil columns for a field lysimeter, and remove intact soil cores.

Georg standing in the finished soil observation pit

The day of Bodentag, participants listened to two hours of lecture/presentations in the morning followed by both lab and field practicum sessions. During the field practicum, attendees could do actual installations of sensors into pit faces. This was useful because there were several researchers there who had Black Forest research sites, and they could look at and ask questions about the challenges of the rocky soil pervasive in that region. We used augers to dig holes to install Decagon sensors so everyone could see how that was done. Georg had one of his Smart Field Lysimeters out there and did a half-field installation. He showed them how to dig the Smart Field Lysimeter down into the soil, scrape the soil off, and actually collect a monolith right there.

After the outdoor practicum session, we went back to the lab where we broke up into small groups. There, people had an opportunity to go see laboratory instrumentation while learning some best practices for making measurements. In mine, people were using the WP4C water potential instrument to figure out the permanent wilting point of the soil that we brought. Attendees also got some careful training on the Hyprop to measure the wet end of the moisture release curve as well as learning about the KSAT, a METER instrument which measures saturated hydraulic conductivity. Because Bodentag is an opportunity to share ideas, we also got a chance to see the multi-step outflow instrumentation developed over the past 20 years by the Forest Research Center there in Freiburg that they use to create soil moisture characteristic curves.

2014 Bodentag attendees

At the end of the day, everyone was exhausted, and we still had a five-hour drive left to get back to Munich. But, everyone had a great time, and the students and researchers who were there learned enough so they could be confident when using an instrument to get the data they need in an experiment. It was a unique opportunity for me to see how to put together a great educational experience, and I am excited to try one here in the U.S. sometime soon: especially if I can run the excavator again!

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Jan 19

Modeling Available Soil Moisture

Both the amount and the availability of water in soil is important to plant roots and soil-dwelling organisms. To describe the amount of water in the soil we use the term water content. To describe the availability we talk of water potential. In thermodynamics, the water content would be referred to as the extensive variable and the water potential as the intensive variable. Both are needed to correctly describe the state of water in soil and plants.

Measuring soil moisture with the WP4C

In addition to describing the state of water in the soil, it may also be necessary to know how fast water will move in the soil. For this, we need to know the hydraulic conductivity. Other important soil parameters are the total pore space, the drained upper limit for soil water, and the lower limit of available water in a soil. Since these properties vary widely among soils, it would be helpful to establish correlations between these very useful parameters and easily measured properties such as soil texture and bulk density. This paper will present the information needed for simple models of soil water processes.

Click here to download the paper.

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Jan 5

Do Funding Agencies Favor Collaboration?

It’s an interesting question, and certainly one scientists need to think about. In a recent conversation a science colleague said, “I think in science right now, all the funding agencies are recognizing that to answer the problems that matter, you need to bring in people from different disciplines and even industry. If you look at the major funding focus of the National Science Foundation, when they consider bio-complexity, they’re not looking for a group of people with the same perspective. Science questions are becoming more complex, so you need to get input from people with varied backgrounds.”

R.J. Cook Agronomy Farm at WSU (http://css.wsu.edu/facilities/cook/)

Examples of this are two projects that METER has collaborated on recently: the Specialty Crops Research Initiative – Managing Irrigation and Nutrients via Distributed Sensing (SCRI- MINDS) and the WSU Cook Farm project, both of which were able to get funding based in part on the use of METER’s technology, and both had a high-level of multidisciplinary involvement.

We got involved in the Cook Farm Project seven years ago because another scientist and I had an idea that fit in the context of a hot topic of the time which was to create a wireless sensor network that was densely populated in a relatively small area. We did this because at that time, scientists were recognizing that many of the processes they were interested in were occurring when they were not out in the field measuring. In order to understand these processes, we needed in situ measurements collected continuously over a long period of time.

What we were trying to do is show that you could create a wireless sensor network in a star pattern, where you have a central point collecting data from a host of nodes surrounding it. Our questions were: can we create a sustainable star network in the field to get consistent and continuous measurements over several seasons, while densely populating the study area with sensors? The measurement network that we designed allowed us to investigate how topography, slope, and aspect interact to determine the hydrology of the soil in this intensely managed agronomic field.

Decagon collaborated with scientists at Washington State University, working with twelve sites across a 37-hectare field. We installed five ECH2O-TE (now 5TE) sensors at 30, 60, 90, 120, and 150 cm below the soil surface.

Wheat field

What we learned was that when wheat plants grow, their roots follow the water down a lot deeper than you might imagine. We observed considerable water loss even 150 cm below the soil surface. Data on soil water potential suggested that, as water was depleted to the point where it was not easily extractable, plant roots at a given level would move deeper into the soil where water was more easily accessible. Soil morphology also came into play as hardpans occurred at several measurement locations and water uptake from layers above and below them showed amazing differences.

It was a really exciting thing scientifically, but also technologically. We learned that the star network was easily possible. It ran autonomously and was very successful, in spite of the fact that the cell phone we used to get the data back to the office never worked very well.

So it was the science question and the technology question together that was able to secure the funding. With those twelve sites WSU was able to secure a grant from the USDA for 4.2 million dollars and the research is still ongoing today. In fact, recently Cook Farm was established as one of the National long-term agroecosystem research sites (LTAR) which will help continue this kind of research well into the future.

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Dec 22

Measuring Osmotic Sap Water Potential

Sometimes networking with new scientists at conferences and workshops can pay dividends in terms of new ideas. Steve Garrity and I recently attended and taught practicum sessions at the PEPg (Plant Environmental Physiology group) Ecophysiology Workshop. The mission of this workshop was twofold: to invite the world experts on plant physiology measurements to come and lecture, and to invite the manufacturers to teach about instrumentation and provide hands-on training.

Workshop participants check the water potential of soil with a UMS T5 mini-tensiometer.

With three sessions per day using METER instrumentation and only two of us, neither Steve nor I could teach about leaf water potential using the WP4C chilled mirror dew point instrument. So, we asked another scientist who is an expert in plant water relations to teach it for us. Not only did he do a great job of teaching about measuring leaf water potential using a hygrometer, but he also inspired us to take another look at how to make this measurement as we learned about its importance to his research (to learn more about how to do this, watch our virtual seminar).

He’s developed a procedure where you can freeze the leaf and break all of the cells so you are left with the cell water (the symplastic water).

Later in the conference, this same scientist gave a talk about the importance of osmotic potential. He’s developed a procedure where you can freeze the leaf and break all of the cells so you are left with the cell water (the symplastic water). He was able to squeeze that sap out and test it in a thermocouple psychrometer, where he established a relationship between how tolerant plants are for drought and what their osmotic sap water potential (turgor loss point) was. We have made many of those sap measurements but had not used them in this manner. That’s really interesting to us at METER because we were unaware of this relationship, and we have now found another use for osmotic potential measurements in leaves.

We would never have realized this new idea without the help of our colleague. Meeting with other scientists at conferences and talking over ideas can be really important. Have you ever struck gold in terms of coming up with new ideas for research, funding, or inventing new research tools at a conference you’ve attended?

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