In the world of specialty crops, there is disagreement on how well weather-driven insect, disease, and frost prediction models actually perform. Dr. Dave Brown, former director of Washington State University’s AgWeatherNet spent years comparing different weather data sources and how those data affect the accuracy of common environmental models used by orchard growers. In this 20-minute webinar, he shares the surprising things he learned.
Decrease chances of crop damage with one simple practice
Find out how you can increase the accuracy of your predictive models and decrease frost, insect, and disease incidents by doing just one thing differently—improving the quality of your weather data. Discover:
Microclimates: what are the conditions like inside a crop canopy versus outside?
Virtual data vs. weather station data: Which is better?
How do site-specific weather data vs. regional network data compare?
How much does a small decrease in data quality affect the accuracy of your models?
What’s the value of in-orchard measurements?
What are some best practices for higher data quality?
For 20 years as a faculty member at Montana State University and Washington State University (WSU) Dr. Dave Brown pursued research on soil sensors, spatial data science, and digital agriculture. At both universities, he served in many leadership roles for major research projects, academic programs, and most recently as Director of the WSU AgWeatherNet program. In this capacity, Dr. Brown hired and supervised a team of meteorologists who pursued research and extension activities focused on evaluating and improving the quality of weather data used for agricultural decisions.
Check out a new podcast made by contributors to the EnvironmentalBiophysics.org blog. We Measure the World is a podcast produced by scientists, for scientists. Application expert Holly Lane and data guru, Brad Newbold interview scientists from all types of disciplines who measure anything and everything about the world to make it better—and more sustainable.
Holly Lane interviews scientists from all types of disciplines
Hang with us to learn a lot and laugh a lot. Explore interesting environmental research trends, how scientists are solving research issues, and what tools are helping them better understand measurements across the entire soil-plant-atmosphere continuum.
Modern technology makes it possible to sample spectral vegetation indices such as NDVI and PRI across a range of scales both in space and in time, from satellites sampling the entire earth’s surface to handheld small sensors that measure individual plants or even leaves.
Figure 1: NDVI is sensitive to the amount of vegetation cover that is present across the earth’s surface (source: low res map obtained from an earth orbiting satellite)
What are NDVI and PRI?
NDVI and PRI are both spectral vegetation indices derived from measurements of relatively narrow wavelengths of reflected light (10 to 50 nanometers) in the electromagnetic spectrum. This is useful for measuring various properties in plant canopies. NDVI stands for the Normalized Difference Vegetation Index and PRI stands for the Photochemical Reflectance Index.
The METER SRS sensor measures both NDVI and PRI and works with ZENTRA Cloud for data visualization in near-real time.
There are many types of spectral vegetation indices, however, this article and the webinar below focus on the theory, methods and application of NDVI and PRI as they are two of the most commonly used (see webinar).
NDVI is especially useful for measuring plant canopy structural properties such as leaf area index, light interception and even biomass and growth, whereas PRI is more useful for getting at functional properties of plant canopies such as light use efficiency. Recent literature shows that PRI is also useful for measuring foliar pigments.
Understanding canopy radiation interactions
To understand where NDVI and PRI come from, it’s important to learn about canopy-radiation interactions. There are three primary fates for electromagnetic radiation as it interacts with plant canopies.
Everybody measures soil water content because it’s easy. But if you’re only measuring water content, you may be blind to what your plants are really experiencing. To understand when to water or plant water stress, you need to measure both water content AND water potential.
Learn more in our soil moisture master class, “Secrets of water in soil“. Six short videos teach you everything you need to know about soil water content and soil water potential—and why you should measure them together. Plus, master the basics of soil hydraulic conductivity.
If you want accurate data, correct sensor installation should be your number one priority. When measuring in soil, natural variations in density may result in accuracy loss of 2 to 3%, but poor installation can potentially cause accuracy loss of greater than 10%.
Proper sensor installation is the foundation for the data you collect. If you have a poor foundation, it makes data interpretation difficult. In this article, get insider tips on how to install soil moisture sensors faster, better, and for higher accuracy. Learn:
What to be aware of when installing sensors
What installation trouble looks like in your data
Installation priorities for soil moisture sensors
How METER is advancing the science of installation for higher quality data
Understand your sensors
To understand why poor sensor installation has an enormous impact on the quality of your data, you’ll need to understand how soil moisture sensors work.
Soil moisture sensors (water content sensors) measure volumetric water content. Volumetric water content (VWC) is the volume of water divided by the volume of soil (Equation 1) which gives the percentage of water in a soil sample.
Equation 1
So, for instance, if a volume of soil (Figure 1) was made up of the following constituents: 50% soil minerals, 35% water, and 15% air, that soil would have a 35% volumetric water content.
Figure 1. Soil constituents
Why capacitance sensors work
All METER soil moisture sensors use an indirect method called capacitance technology to measure VWC. “Indirect” means a parameter related to VWC is measured, and a calibration is used to convert that amount to VWC. In simple terms, capacitance technology uses two metal electrodes (probes or needles) to measure the charge-storing capacity (or apparent dielectric permittivity) of whatever is between them.
Figure 2. Capacitance sensors use two probes (one with a positive charge and one with a negative charge) to form an electromagnetic field. This allows them to measure the charge-storing capacity of the material between the probes.
Choosing the right weather station can be confusing. Hundreds of options exist for weather monitoring ranging from $200,000+ aviation-grade observation systems to $25,000 WMO-grade mesonet stations with redundant rain gauges and multi-height wind and temperature observations, all the way to $300 hobbyist-level stations.
Dr. Cobos is a Research Scientist and the Director of Research and Development at METER. He also holds an adjunct appointment in the Department of Crop and Soil Sciences at Washington State University where he co-teaches Environmental Biophysics. Doug’s Masters Degree from Texas A&M and Ph.D. from the University of Minnesota focused on field-scale fluxes of CO2 and mercury, respectively. Doug was hired at METER to be the Lead Engineer in charge of designing the Thermal and Electrical Conductivity Probe (TECP) that flew to Mars aboard NASA’s 2008 Phoenix Scout Lander. His current research is centered on instrumentation development for soil and plant sciences.
In case you missed them, here are our most popular educational webinars of 2019. Watch any or all of them at your convenience.
Lab vs. In Situ Water Characteristic Curves
Researcher Running A Hand Across Wheat
Lab-produced soil water retention curves can be paired with information from in situ moisture release curves for deeper insight into real-world variability.
Researcher is Collecting Data from the ZL6 Data Logger
METER research scientist Dr. Colin Campbell discusses how ZENTRA Cloud data management software simplifies the research process and why researchers can’t afford to live without it.
Dr. Gaylon Campbell shares his newest insights and explores options for water management beyond soil moisture. Learn the why and how of scheduling irrigation using plant or atmospheric measurements. Understand canopy temperature and its role in detecting water stress in crops. Plus, discover when plant water information is necessary and which measurement(s) to use.
Soil Moisture 302: Hydraulic Conductivity—Which Instrument is Right for You?
Leo Rivera, research scientist at METER teaches which situations require saturated or unsaturated hydraulic conductivity and the pros and cons of common methods.
Predictable Yields using Remote and Field Monitoring
New data sources offer tools for growers to optimize production in the field. But the task of implementing them is often difficult. Learn how data from soil and space can work together to make the job of irrigation scheduling easier.
We interviewed Gaylon Campbell, Ph.D. about his association with one of the founders of environmental biophysics, Champ Tanner.
Who was Champ Tanner?
Champ Tanner was a dominant scientist in his time and a giant among his colleagues. He was the first soil scientist to be elected a member of the National Academy of Sciences: the highest honor a scientist can achieve in the United States. Some may not realize that throughout a career filled with achievements and awards, he battled the challenges of a debilitating illness. He didn’t let that limit his passion for science, however. His efforts to understand and improve measurements generally went beyond those of his fellow scientists. One of his colleagues once said of him, “Champ’s life exemplified goal-oriented determination and optimism regardless of physical or financial impediment.”
Dr. Tanner was one of the pioneers in applying micrometeorology to agriculture.
What were his scientific contributions?
Champ was an extremely careful experimentalist who was gifted at developing instrumentation. He started out making significant contributions in soil physics such as improved methods for measuring water retention, particle size distribution, air-filled porosity, and permeability. He was one of the pioneers in applying micrometeorology to agriculture and was passionate about finding ways to improve the precision and reliability of measurements. No measurement was too difficult. He designed and built his own precise weighing lysimeters which provided measurements of evapotranspiration in as little as 15 minutes. Later, he switched to plant physiology, reading almost every published paper on the subject and then building his own thermocouple psychrometer and plant pressure chambers, making important contributions in that field.
His largest contribution, however, was the measure of excellence he inspired in the students that he trained. I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have. They’ve all made enormous contributions in many different fields. Perhaps it was because he was a pretty hard taskmaster. He expected the students to meet a standard, and the ones that struggled with that had a hard time. In fact, to this day one former student complains, “About once a year, I have a nightmare in which Champ appears.”
I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have.
Champ wanted his students to measure up, but he also cared about them. His fellow scientist, Wilford Gardner, described him this way, “There was a transcendent integrity to his personality that permeated everything he did. He could be blunt, candid and forthright, but he was never lacking in compassion and concern for students, colleagues, and friends.”
What was your association with him?
I had a wonderful relationship with Champ, although I wasn’t one of his students. One of his former students came to WSU as a visiting scientist and told him about what I was working on. As a result, he brought me into his inner circle of associates and played a vital role in the success of my research. This association even extended to my family who were with me on one of my many trips to Madison. Despite my numerous and occasionally unruly progeny, he and his wife welcomed us like long lost relatives and made each of the children feel special. That’s who they were: the most caring and outgoing people.
Champ also had a sense of humor. He used to call me up to have long discussions about science, and because he was two time zones ahead, it would get pretty late for him. We’d be having an intense discussion about experimentation, and all of a sudden he’d stop and say, “Oh, I’d better cut this off, or I’ll get home to a cold supper and a hot wife.”
What kind of a person was he?
If you worked in his lab, you needed to tow the mark. You didn’t leave tools around, and you didn’t mess them up. If you left out a screwdriver, you’d find it on your desk the next morning with a terse note. And if you took the diagonal pliers, cut some hard wire with it and left some nicks, those would be on your desk too. It was a sort of tough love, but he used it to train his students to the highest possible level.
He taught his students to be rigorous in their measurement protocols
He wanted his students to stand up and argue for their point. If you were the kind of person that could stand your ground and put up a good defense, he loved that. Gardner described Champ in this way, “His work hours were legendary. His standards of science and personal integrity were almost unrealistically high. The stories his students now pass on to their students may sound apocryphal to those who did not know Champ. But it was impossible to exaggerate where Champ was concerned.”
What do you think scientists today can learn from him?
What we can learn from Champ Tanner is not to fool ourselves. He thought you should try to come to an answer in a few different ways, to be sure that it really was the answer. He taught his students to be rigorous in their measurement protocols in order to get the noise out of their experiments. He wanted them to dig to the bottom of problems and understand the details. In his mind, you couldn’t be a scientist and rely on somebody else to figure out heat transfer or radiation. He thought you should understand it well enough that you could defend it yourself.
You can read more about Champ Tanner’s life and scientific contributions in this biographical sketch, written for the National Academy of Sciences when he died.
Dr. Stuart Campbell, professor of Biomedical Engineering at Yale University has been toying with the idea of using soil moisture sensors to measure tissue edema in human subjects.
Tissue edema occurs when too much fluid leaks from your capillaries into your tissue.
He says he got the idea from Dr. Ken Campbell, former professor of Bioengineering at Washington State University: “I was explaining to Dr. Campbell about the sensorsMETER makes, and he pointed out that there are many diseases where you might want to measure someone’s tissue edema, and it would be interesting to see if you could use a soil sensor in a wearable device to help doctors monitor swelling in their patients, much like a heart monitor monitors heart activity.”
Tissue Edema:
Tissue edema occurs when too much fluid leaks from your capillaries into your tissue. Capillaries, the smallest blood vessels in your body, are somewhat leaky, allowing the exchange of nutrients and waste between the tissue and the blood. The fluid that surrounds the blood cells is free to exchange across the capillaries, and edema will occur when too much fluid leaks out of the circulatory system into the tissue. Edema can be caused by things like heart disease, pregnancy, or standing on your feet all day.
What Makes the Fluid Leak?
In soil, water moves from high water potential to low water potential. Similarly, there are forces inside the circulatory system that cause the transfer of fluid between capillaries. Your blood vessels have a certain amount of pressure that is generated by your heart. If your blood pressure goes up, it can cause edema. Dr. Stuart Campbell says, “The actual fluid pressure is part of what decides how much fluid is pushed out, but it’s not that simple. Your blood has large proteins that are too big to get out of the capillary. That means the more water that leaves the capillary and moves into the tissue, the more concentrated those proteins become, which lowers the water potential (or osmotic potential) of the blood. This delicate balance is what prevents too much water from leaking out. However, if you have a disease that tips this balance, either through high blood pressure or a condition that allows those proteins to leak out of the capillary, edema would occur because you don’t have the osmotic potential pulling the water back into the capillary and keeping the proper balance.”
Dr. Campbell thought it would be interesting to figure out if he could monitor the edema of heart tissue during one of the procedures.
The Heart Experiment:
Dr. Campbell decided to see if a soil sensor would work to measure animal tissue when he was working as a summer student in the Visible Heart Lab at the University of Minnesota. Campbell says, “Similar to a human heart transplant, this lab is able to keep pig hearts alive outside the body. The problem, however, is that they use a manmade solution instead of blood, and that imitation blood is not ideal. If the composition of the fluid is not perfectly adjusted, you can have problems with your experiments. I thought it would be interesting to figure out if we could monitor the edema of the heart tissue during one of the procedures. I hooked up the soil probe and used it in one experiment where I put it in contact with the heart while it was beating. There was, in fact, a change in output of that signal during the experiment. But, because I only got one chance at it, it was inconclusive as to whether this was indicative of an imbalance in the composition of our artificial blood substitute.”
An Anecdotal Experiment:
Still curious to see if the idea would work, Dr. Campbell decided to try one more experiment: this time on his wife who was experiencing edema symptoms after childbirth. He says, “It occurred to me that this was an opportunity to try out the soil moisture probe one more time to measure tissue edema. So each day, I would measure her ankles, putting the probe in flat contact with her skin while tightening a strap gently.” Dr. Campbell says he watched the swelling go down as the numbers on the probe got smaller, and comments, “It was anecdotal evidence that at least in extreme cases, you might be able to get the soil probe to work. But I still have questions, such as, how would you make sure that the probe was always touching the skin in the same way? And, if the person got sweaty, would that change the soil probe reading?”
There are millions of people in this country who have heart failure.
Why the Experiments Should Continue:
Though Dr. Campbell hasn’t had time to pursue the experiment further, he feels that if the idea works, it has the potential to improve lives and save our nation billions of dollars. He says, “There are millions of people in this country who have heart failure. Maybe they’ve had a blockage in one of their coronary arteries, or perhaps their heart is worn out because of age. You can tell when someone is in heart failure because when they lie down to go to sleep at night, all that fluid makes its way slowly from the ankles, through the legs, the torso, and eventually into the chest. The problem is that the lungs are very delicate, and when you have edema in the lungs, it’s almost like you have pneumonia. This type of sensor could be an easy way for people to monitor themselves and manage their fluid intake and diet after they get home from the hospital.” Dr. Campbell says this helps the economy because if people don’t manage their fluids, they have to return to the hospital so they can be supervised to eat correctly and regain the proper fluid balance. This ends up costing the economy billions of dollars unnecessarily. He concludes, “Perhaps people just need to follow instructions, but it’s possible with better monitoring that the situation can be improved.”
During a recent semester at Washington State University, a film crew recorded all of the lectures given in the Environmental Biophysics course. The videos from each Environmental Biophysics lecture are posted here for your viewing and educational pleasure.
Dr. Khot and his postdoc, Dr. Jianfeng Zhou, are using leaf wetness sensors to determine if and how long water is present on cherry tree canopies after a rain event. Dr. Khot hopes that data from these sensors will help growers decide whether or not it makes sense to fly helicopters in order to dry the canopies.
Dr. John Selker, hydrologist at Oregon State University and one of the scientists behind the Trans African Hydro and Meteorological Observatory (TAHMO) project, gives his perspective on the future of sensor technology.
Michelle Newcomer, a PhD candidate at UC Berkeley, (previously at San Francisco State University), recently published research using rain gauges, soil moisture, and water potential sensors to determine if low impact design (LID) structures such as rain gardens and infiltration trenches are an effective means of infiltrating and storing rainwater in dry climates instead of letting it run off into the ocean.
Looking up at a tree canopy
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