Environmental Biophysics

Apr 4

Double Ring Infiltrometers Versus DualHead Infiltrometers

Several years ago I had the chance to work at the USDA ARS Research Watershed in Riesel, Texas. The goal of my research was to look at the effects of land use and landscape position on water infiltration. Within the research watershed there is preserved and maintained native prairie, improved pasture, and conventional tilled areas, which have been in existence for 75 years. Thus we were able to use infiltrometers to study the long-term effects of those different land uses, along with the effect of landscape position within the same soil type.

Texas Infiltrometer setup

My research focused on the Houston Black Soil Series, which is a clay-rich soil with a high shrink-swell capacity. This soil type has key economic importance, as it is present in much of Texas’ USDA prime farmland. To achieve our objectives, we began by mapping soil bulk electrical conductivity using an EM38 device (electromagnetic geo-surveying instrument). The maps we created allowed us to look for areas of variability in water content, depth to parent material, clay content, and salinity. Then we randomly selected three zones within the catinas (full hill slope including summit, back slope, and front slope) and flagged them with GPS points. Our goal was to make infiltration measurements at all of the landscape positions on the slope and compare them to the same landscape positions within each land use type.

We found that the native prairie had the highest infiltration rates because the soil maintained its strong structure and macropores which allowed water to conduct well through the soil. We also found some differences by landscape position that were consistent within the different catinas. As water would run down the catina, erosion would transport soil and organic matter off the shoulder and back slope and deposit it on the foot slopes. Even though they were mapped as the same soil type, the differences in erosion and reduction of organic matter affected the ability of these different positions to transport water.

We chose to customize existing double ring infiltrometers to make these measurements because there wasn’t anything automated on the market. If I was going to conduct my research in a reasonable amount of time, I had to come up with a system where I could run a lot of measurements relatively easily. As a result, we bought three double-ring infiltrometers and modified them with pressure sensors and some larger controlled ports. The resulting setup was huge; the outer ring on each infiltrometer was 60 cm in diameter and the entire instrument was very heavy. We were constantly refilling the instrument water reservoirs. In fact, this setup required so much water that we had to pull a 1,900-liter water tank on a trailer wherever we were taking measurements.

Our goal was to save time by running all three infiltrometers concurrently, but it still took a LONG time. Even though we had automated the instruments, they required a lot of monitoring; sometimes I had to fill our 1,900-liter water tank twice in a day. One measurement at one site took anywhere from 1.5 hours to 3 hours depending on when we reached steady state. We spent so much time out in the field that we were actually caught on film in one of the Google Maps picture flyovers! Even after all this field time, the data analysis was overwhelming, despite a relatively seamless approach to handle it all.

Our huge setup caught on google maps

I often dreamed of making a tool that would be a lot easier for me and others to use. When I joined Decagon (now METER), it gave me an opportunity to do just that. Our design goals were to make an infiltrometer that required less water and simplified the data analysis. We rejected the double ring design in favor of a single ring approach because research has shown that the outer ring doesn’t buffer three-dimensional flow like it’s supposed to. (Swartzendruber D. and T.C. Olson. “Sand-model study of buffer effects in the double-ring infiltrometer” Soil Sci. Soc. Am. Proc. 25 (1961), 5-8)

We also wanted to simplify the analysis of three-dimensional flow. With a constant head control in a single ring, there are equations that you use to correct for it. But you have to guess at things like soil type and structure which leads to inaccuracies. Multi-head analysis has been around for decades. It involves establishing constant water heights (heads) at multiple levels and looking at the difference in the infiltration rates to calculate the sorptivity. Thus, parameters that are normally estimated from a table can actually be measured, and infiltration results will be independent of users.

Still, there can be problems with the multiple head approach. Increasing the water height when infiltrating into a really low conductivity soil may take 1 to 2 hours to drain back to the original height. We didn’t want to make this measurement take longer than necessary, so instead of using additional water, we used air pressure to simulate higher water levels which can be added or removed very quickly.

So, thanks to the instrument hardships I endured in my past efforts to obtain infiltration measurements, we now have an easy-to-use dual-head infiltrometer (now called the SATURO), that can do the analysis of infiltration rates and saturated hydraulic conductivity on the instrument itself (it gives sorptivity and alpha, based on the soil type and structure, and makes the correction onboard). Thus, if a scientist needs a value right away, it’s there. But, if like me, they wanted to dig deeper through the data, all the measured values can still be downloaded for more careful analysis. Together, it’s a simple tool for both scientists and consultants who need to make these measurements. And they won’t get caught on Google Maps like me, because they’ve had to spend their whole life in the field taking measurements.

Below is a video of the dual-head infiltrometer in action.

Get more information on applied environmental research in our

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

LinkedIn Facebook Messenger X Reddit Threads Email Copy

Mar 27

The Right Auger For Water Content Sensor Installation

Traveling around the world, I’ve seen many ways to install soil moisture sensors. Digging a trench to the required depth and inserting the sensors into the sidewall is certainly the most common technique. But using a shovel takes a lot of effort, especially in rocky soil. To solve this problem, I like to use an auguring tool because of its ability to dig through soil to deeper depths without taking a lot of time. Also, the footprint of an augured hole is also only a few inches, which makes for a much cleaner installation. Still, borrowing an auger from the lab next door and heading to the field may not be the best option. This is what we did on the Cook Farm project a few years back.

Standard bucket auger (image: www.atlanticsupply.com)

The Cook Agricultural Farm is a 37 Ha managed research site near Pullman, Washington where a combined team of Decagon and WSU scientists installed 150 water content sensors over 30 sites a few years ago. At each site, we used the techniques outlined in METER’s installation video, which can be found here. However, the hardest thing about this installation was that we used some borrowed, standard bucket augers to bore the holes. These had a cutting surface along the bottom and an enclosed cylinder to hold the soil. Once we filled that bucket, we had a difficult time getting the soil out which really slowed the installation.

Researcher Digging Soil Out of the Bucket Auger

Ben digging soil out of the bucket auger during the Cook Farm Installation, 2009.

Recently while traveling to Germany, I learned about the Edelman Auger. The company that makes these (Eijkelkamp), says that most people in America use bucket augers to bore into fine soils which is needlessly time consuming. Edelman Augers, originally designed by the Army to dig latrines, will save time and labor.

Edelman auger.

At first, I was skeptical. It only had two cutting blades that ran up the auger in kind of loop; how would the soil lift out of the hole? However, when I tried one later in the day, the auger cut through the soil, making a 10 cm hole with very little effort, and as I removed it, the soil came out easily. It wasn’t hard to get the soil out from between the blades because there was no enclosed cylinder for the bucket. I wish I’d known about this auger when I was trying to install sensors at the Cook Farm.

So, here are a few tips about augers to help you pick the best one for your work:

The Eijkelkamp Edelman augers are best for silty soils to clay soils so pick this one if you’re working in sites with these types of soils. It’s also great for digging a quick latrine.

Bucket augers are best for sandy soils because of the enclosed cylinder will help lift the loose sand out of the borehole.

If you’re trying to install your soil moisture sensors in very rocky soils, try a stony soil auger. It has big blades to help move small rocks and lift them out of the hole.

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 23

1 Comment

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 23

1 Comment

Are Arduinos Practical and Cost Effective?

Last spring my daughter, Sarah, needed a project for the science fair, and since she has always been interested in scientific measurements, we decided to try and figure out when it was time to water her mother’s plants. Since we’ve fielded a lot of calls from customers asking about using Arduinos (user-programmable microprocessors) lately, I thought I would kill two birds with one stone and give one a try. My preference would have been the speed and simplicity of a METER data logger, but I was curious about how practical and cost-effective this method might be for taking measurements.

Young Girl Concentrating on Helping with the Soldering

Arduino Science Project with my daughter

The Arduino is an inexpensive, user-programmable microprocessor on a circuit board that has exposed analog inputs for measuring voltages and digital ports for measuring incoming digital signals. It can also run displays and is programmed by an Arduino IDE running on your computer.

I purchased a book called Arduino Recipes that taught us the basics of Arduino programming, which was pretty straightforward. The Arduino board itself has rows of pinheaders, so I brought some of the male pinheaders from work and soldered all the wires to them, in preparation to attach the water content sensor. It looked medusa-like with all the wires coming off the pinheaders, but we could then just hook up kid-friendly snap circuits and try some elementary tests to get used to the system.

We hooked up Decagon’s (now METER) analog water content sensor (EC5) first and started measuring. It has a really nice calibration equation supplied by METER, so we used that for a while to measure water content. We took one of mom’s dry plants and measured before and after watering and used the readings to make a linear relationship between the reading on the sensor when it was dry and the reading on the sensor when it was wet.

Our biggest challenge was that Sarah wanted to display this to mom to make sure she knew when to water the plants. So she and I then had to figure out how to integrate an LCD display.

Sarah was excited to get the digital soil moisture sensor integrated because we could then measure water content AND electrical conductivity (EC) to get an idea of the fertilizer in the soil. We used my work colleague’s code to read the digital sensor output, which worked quite well. It only took a few minutes to insert his piece in the code into our program and start reading water content. Our biggest challenge was that Sarah wanted to display this to mom to make sure she knew when to water the plants. So she and I then had to figure out how to integrate an LCD display. Luckily, all the details were on the Arduino website. We just cut and pasted the code into our program and then did all the wiring.

Finally, we had it all put together, and we inserted the 5TE digital sensor into the pot. It worked, but the device was large and unwieldy. Mom wasn’t happy that we were putting it right in the middle of her clean living room, but Sarah pointed out that we have to make sacrifices for science, so we put the sensors in the soil, set up the display, and ran it for about a week. Sarah took water content data morning and night and watered it when it reached our “dry” point. She took the finished system to the science fair and was excited to find a few future customers.

The biggest challenge would be all the details in the system. We’d need a circuit board, a power supply, a data logging interface board, and a box to put it in, and if we were going to set it outside, that box would have to be waterproof.

Are Arduinos practical for use in your experiments?

It depends. Sarah and I found out that it just doesn’t take a lot to integrate a sensor into the Arduino system and be able to make measurements. However, if we were to try the above experiment long-term, the biggest challenge would be all the details in the system. We’d need a circuit board, a power supply, a data logging interface board, and a box to put it in, and if we were going to set it outside, that box would have to be waterproof. We’d also need ways to connect the sensor to the circuitry, and all these things take time and resources. For me, the take-home message was that Arduinos are a lot of fun, and might fit your application exactly the way you want. However, you’ll need time (often a lot of it) to spend making sure it’s waterproof, doing all the programming, writing a code durable enough to fit your field applications, and getting the hardware prepped. In fact, Decagon support staff take calls every week from frustrated do-it-yourselfers who’ve found this is not as easy as it seems. Thus, in my opinion, an EM50 or Campbell Scientific data logger are more practical options than an Arduino-like microprocessor.

Are Arduinos cost effective?

A lot of scientists want to make measurements out in the field with small budgets. I am certainly one of those. Arduinos are $85 versus a complete data logger that costs several hundred dollars. However, people tend to forget that things like labor even cost discrepancies.

So, if you have plenty of time, want the versatility, and you love this stuff, go ahead and make an Arduino sensor, but at the end of the day, the cost shouldn’t be a driver, because there are data loggers that can do the job of an Arduino more simply and quickly, without all the hassle.

Download the “Researcher’s complete guide to SDI-12″—>

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