At the Western Region International Plant Propagators Society (IPPS), the Pacific Northwest Insect Management Conference (PNWIMC), and the Orchard Pest and Disease Management Conference (OPDMC) last month, we presented cutting-edge research and advancements in our field. Our presentations at the Western Region IPPS and PNWIMC focused on the latest developments in sensor-controlled irrigation, and flatheaded borer management, respectively.
At the Orchard Pest and Disease Management Conference, we discussed the latest techniques in IPM for managing powdery mildew with biological fungicides applied by our laser-guided Intelligent Sprayer system. Through our presentations at these conferences, we aim to advance the knowledge and understanding of plant health in our field and to promote collaboration among professionals. By sharing our research and engaging in discussions with our peers, we strive to advance the science of horticultural production to support the growth and success of the horticulture in the Pacific Northwest region.
At NWREC, we have been working on our new hydroponic greenhouse project. However, since October we have encountered construction challenges in connecting the natural gas heaters, which has impacted the growth of crops such as lettuce, tomatoes, and cucumbers. As a result, lettuce growth has been slow and plagued by Botrytis, and warmer-growing crops like tomatoes and cucumbers have fared even worse. We are working to resolve the permitting issues with the heaters as soon as possible and look forward to updating you on the progress of the greenhouse project in the coming year.
For the past few years we’ve limited gatherings on the farm due to COVID-19 restrictions. In the summer of 2022, however, we were finally able to welcome the public back for Nursery Program Field Days. We’d like to take this opportunity to boast about a few of our highlights from the last several months.
For the first time, the Nackley Nursery Production team was an official stop on the Oregon Association of Nurseries Farwest Innovative Production Grower Tour. Our portion of the tour at NWREC showcased sensor-controlled irrigation, heat-stress mitigation techniques, LiDAR smart-sprayer systems, and practices that can reduce boxwood blight spread, and methods of scouting and monitoring insects in nurseries and greenhouses. These projects offer a wide range of savings for growers.: up to 80% improvement in irrigation efficiency, up to 70% reduction in sprayed pesticides, and a significant reduction in boxwood blight infection.
The second big event was an open house for our Climate Ready Landscape Plant trial, the largest coordinated landscape plant irrigation trial in the Western US. Plant professionals from around the region came to rate plants and discuss how we, as a society, are going to maintain healthy landscapes while faced with increasing extreme weather.
Ongoing projects that will continue this year include, research by our graduate student Sadie Keller, who is investigating Oak and Maple drought tolerance. This summer, Sadie shared her preliminary findings with scientists at the American Society for Horticultural Science, in Chicago.
In addition, Dr. Melissa Scherr continues our research on the Pacific Flatheaded beetle, with the anticipation of a grower event hosted at NWREC discussing current research on Flathead Borer biology and control this coming April – 2023.
The tour route will travel through fields with uneven terrain. Farm cart transport (e.g. gators) can be available for those who request assistance.
Schedule of Events
Field Tour 11 :00 -11:15 Station 1. Welcome, overview of the program and biostimulant research on Shade-Trees 11:15 – 11:30 Station 2. Plant-based irrigation scheduling: pressure bomb and infra-red thermography 11:30 – 11:45 Station 3. ET-based irrigation scheduling and Flatheaded borer research 11:45 – 12:00 Station 4. Cover cropping and Heat-stress prevention 12:00 – 12:15 Station 5. Boxwood blight control 12:15 – 12:30 Station 6. LiDAR “smart” air-blast sprayer and drone demonstration
12:30 – 1:00 Station 1. Open chat with research team, refreshments and grilled sides.
Open House 1:00 – 2:00 Self guided tour. Researchers will be at each of the six stations to answer questions. Sprayer demos will take place at station 6 every 15 mins.
Shade tree growers need to be prepared for the effects of climate change in Oregon.
In order to equip growers with the tools necessary for production success, we aim to determine critical shade tree stress thresholds, characterize plant responses to drought conditions, and correlate remotely collected spectral images with ground based plant water stress measurements.
Previous studies have sought drought response measurements for Acer rubrum (Red Maple) and Quercus rubra (Red Oak), but never in a nursery production setting.
We aim to disseminate this information to Oregon shade tree growers at the completion of this experiment with the hope to aid growers in making data driven irrigation decisions and demonstrate the use of these technologies in nursery production settings.
In Oregon’s Willamette Valley, the heart of the nursery country, rainfall is scarce during the summer and humidity is low. Oregon’s dry summer conditions can lead to low moisture stress conditions for maples and oaks in normal years. Plant stress resulting from low soil moisture, high heat, and low relative humidity have been exacerbated in recent years with the increasing frequency of heatwaves and drought. Drought and heat stress scorch the maple and oak canopies, which can lead to decreased plant quality and economic losses for shade tree growers. Sensor-based technologies can be used to model plant responses to environmental gradients to develop warning systems to help growers prevent stress and bridge a knowledge gap in the nursery production industry regarding drought responses.
How are we studying plant stress responses?
Starting late June 2022, we will implement two irrigation treatments (well-watered and drought) in our shade tree planting with each row having independent irrigation control. The well-watered rows will be maintained at a soil water potential of >-1.0 mPa. The drought treatment rows will be allowed to naturally dry down to a soil water potential of -4 mPa. If during the experiment, our metrics (stomatal conductance and stem water potential) do not show considerable responses at -4 mPa tension, we will allow the drought treatment to continue to dry down progressively (-1 mPa) until stress is evident.
Why and how do we measure stem water potential?
Plant water status is commonly defined in terms of water potential or the ability of the water to do work. In most cases, well watered plants have “high” water status and drought conditions lead to a “low” water status (Levin and Nackley 2021). Using the pressure chamber, we will take midday stem water potential measurements twice weekly from 12pm-3pm. This time frame is important because it represents the time of day where leaf transpiration is at its maximum.
First, we will cover the leaf and stems to be measured with an opaque bag for at least 10 minutes before pressurization to allow the plant to stop transpiring. Once we excise the sample from the tree it should be placed into the pressure chamber or “pressure bomb” within 30 seconds (Levin 2019). Once the stem is placed into the chamber and pressure is applied, the amount of pressure that it takes to cause water to appear at the cut surface tells us how much tension the stem is experiencing.
Why and how do we measure stomatal conductance?
We measure stomatal conductance using a porometer that measures the degree of stomatal openness and the number of stomata (Licor.com). This indicates the plant’s physiological response to its current environment. If a plant is stressed, it will tend to close its stomata and lower the stomatal conductance rate. We will be using a combination of the LI-6800 Portable Photosynthesis System and the LI-600 Porometer/Fluorometer to make our measurements twice a week from 12pm-3pm.
For more information:
Please stay tuned in the coming months for more blog posts about how we will find plant stress thresholds by measuring the hydraulic conductivity of these shade trees. We will also correlate remotely collected spectral and thermal images with our ground based plant stress measurements to demonstrate how implementing a UAS equipped with a multispectral and thermal camera can be used to detect water stress in nursery production.
I grew up in a small rural town in East Texas, deep behind the piney wood curtain in a land dominated by giant loblolly pines, muddy windy rivers, and air so thick and humid it felt like you were wearing it. When was a teenager I mowed lawns and fixed up garden beds. One client I had, Miss Trixie, was getting on up in her years. She had an amazing green thumb but her age had was limiting her mobility. She would coach me through everything I did – pulling weeds, planting annuals, pruning, and fertilizing. She left me with a love of horticulture that I will carry until the end of my days.
I enriched that love by getting a BS in Horticulture at Texas A&M. While I was there I worked as a student worker for a rose and peach breeder. It was where I first learned about the land grant system and the mission of extension, and I thought at the time that is sounded like a really fun job. I also met my wife through that job. She was a horticulture student as well, and she worked on the roses and I worked on the peaches. We just never stopped hanging out, now we have been married for almost 10 years.
After I graduated from Texas A&M I enrolled in a Masters International program at Oklahoma State University. The program merges graduate school and serving in the United States Peace Corps into one. After a little over a year of studies at OSU my wife and I were sent to Panama to serve as volunteers in an indigenous community deep in the rain forest near the Columbian border. My time in the Peace Corps was good, but also very challenging. We lived in one of the most remote sites of any of Peace Corps Volunteer in the world at that time. Illness and isolation were persistent challenges, but it was very rewarding work. We taught home gardening, and worked on clean water projects. When we left many folks in our little village of 100 people were growing their own veggies for the first time.
When we returned from Panama, I took a job for a year working for Texas A&M Extension and Research doing an irrigation trial on dent corn in the high desert of Arizona. I lived and worked on a couple 1000 acre farm and learned a great deal about irrigation. A family illness brought us back to East Texas, and we became teachers. We taught high school biology and environmental science for 5 years. We used our summer breaks and holidays to build a house. Little by little we built the whole thing ourselves in cash over 4 years. After resting for 1 year we decided that we were tired of living in such a hot and humid place and decided to pack up and move “somewhere you can see mountains”. In June of 2019 I got a job working for the Small Farms Program here at NWREC and we moved to the great Pacific Northwest and never looked back.
Living and working in the Willamette valley is such rewarding experience. It is truly a horticultural paradise, with some world class soils and growers. I get do something a little different every day, sometimes installing research trials or putting together workshops for growers, and there are always endless opportunities to hone my horticultural skills.
Nurseries grow a wide variety of species and use many different crop production methods which can make effectively scheduling irrigation difficult.
Mini-lysimeters are devices that measure evapotranspiration (ET) via a change in weight of a containerized crop.
Mini-lysimeter controlled irrigation has shown to reduce water use and conserve nutrients while producing plants of marketable size and quality.
The need for sensor-controlled irrigation
Irrigation scheduling for nursery is complex due to the wide variety of species grown, the variety of pot sizes, the differences in growing media, and differences in environmental conditions (i.e. greenhouses, hoop-houses, field nurseries, or use of shade cloths). These factors all influence the specific crop water requirements, making it difficult to determine a generalized irrigation solution. As such, irrigation scheduling is commonly based on grower intuition and experience. For example, it is common for an experienced grower to pick up pots as they walk through a can-yardto get a feel for the weight and irrigation need. With funding support from the ODA-OAN research program, we sought out to develop an automated sensor-controlled irrigation system that is based off container weight, referred to as a mini-lysimeter controlled irrigation system.
What are lysimeters?
Lysimeters are devices that directly measure crop evapotranspiration (ET), which is the transfer of water from the soil to the atmosphere through plants by transpiration, and from the soil by evaporation. Lysimeters consist of a tank filled with soil and crop that is placed on a scale. Any change in weight of the tank is a direct measure of water moving in or out of the system. This provides a direct measurement of water consumption from the tank’s boundary, which can be used to inform irrigation scheduling. Lysimeters have historically been used in agronomic crops like wheat, alfalfa, or legumes. However, they can be scaled down for use in nursery and greenhouse crops, which are often referred to as mini-lysimeters (Fig. 1). You can read more about mini-lysimeters and their many applications in our recent publication.
System Design The mini-lysimeter controlled irrigation system at the NWREC consists of 16 mini-lysimeters. They are suitable for measuring up to 10kg (22 lbs.), which can accommodate up to a 3-gal container (Fig. 2). The mini-lysimeters are hooked up to a Campbell Scientific CR1000X data logger (Campbell Scientific Inc, Logan, UT) using a multiplexer. The system is programmed to trigger irrigation for a zone based on the average container weight. This ensures that the applied irrigation is representative of the variability between containers, such as differences in the water holding capacity of the media, and irrigation uniformity. A guide detailing the design, calibration, and performance of the mini-lysimeter controlled irrigation system and can be found here.
System Performance When mini-lysimeter controlled irrigation is compared to traditional irrigation methods (i.e. irrigation on a timer), it has shown to use less water while producing plants of equal size and quality. Read more about this study here. Mini-lysimeter-controlled irrigation also responds more effectively to the seasonal and daily variations in water demand, increasing irrigation frequency during hot and dry conditions, and foregoing irrigation during cooler days or after rain. This is particularly salient as extreme weather events become more frequent. Having another set of eyes (sensors) looking over your crops can help reduce losses from over- and under-watering.
I was born and raised in Southern Oregon (Central Point, OR). I grew up with a family that spent a lot of time outdoors, and almost always around water. White water rafting, crabbing trips, skiing, surf lessons, and sailing was how I spent most weekends and summers. Not much has changed. I have always been a tinkerer and love being creative, solving problems and building. My up bringing, laced with unintentional physics lessons, paired with a love for math and science led me to pursue a degree in Mechanical Engineering at Oregon State University.
During undergrad, my path of study provided me with many unique and exciting opportunities. My favorite of which was studying abroad at the University of New South Wales in Sydney, Australia. This was such an incredible experience that widened my world view and got me passionate about international travel. I then got involved in the OSU chapter of Engineers Without Borders, and in my last year of undergrad I traveled to rural Cambodia on an assessment trip to plan out the design for a water distribution and filtration system for a small village. It was a powerful and transformative experience, as I was able to see the complexity and challenges of water resource issues globally. We learned a lot from the community and local NGOs about project management, engineering in low-resource environments, and the challenges associated with regulating a common-pool resource like water. Ultimately, it was during this experience that I realized I wanted to be in a profession where I could contribute to solving global environmental problems, which led to my M.S. in Water Resource Engineering with a research focus on precision agriculture from the University of Idaho.
Now, as an FRA in the Nackley Lab working on sensor-controlled irrigation techniques, I am lucky to have found a niche career path that combines engineering and environmentalism. I investigate and develop automatic irrigation systems that use real-time feedback from plants, soil or weather (or a combination thereof) to control irrigation and conserve resources. My favorite thing about working in agricultural research and extension is the great potential for impact. At the extension level, we are at the very important nexus of academic research and on-farm adoption. Working closely with growers to develop pertinent research questions, and having growers anticipate our experimental results gives our work tangible purpose and keeps things exciting.
I was born in the small farming village of Los Angeles. I lived in the city doing office type jobs until I turned 25 and read a book about the soil microbial community; and everything changed. This book, ’Teaming with Microbes’ by Jeff Lowenfels, is responsible for my complete career change. It was written so the first half taught the science behind soil and plant interactions while the second half explained how to use this knowledge in a home garden.
At the time I lived in a 3rd story apartment building with a balcony that, in no time, was overflowing with vegetable plants and bubbling buckets of compost tea. The success of the garden was directly related to my new-found understanding of soil. I moved out of California and went back to school at the age of 30 to follow my new found passion. My first class was Soil 101 at the local community college in Clackamas. Learning about the “why” behind life science fascinated me. I quickly finished a two year degree and transferred to Oregon State University.
Majoring in Crop and Soil Science while working in a soil microbiology lab took up all my time; when I wasn’t on my daily commute of 160 miles or staying up all night with two young daughters who didn’t like to sleep. After completing my bachelor’s degree, I joined the Dragila Lab and began working on my master’s degree in Soil Physics. I loved doing research and worked on a large, multi-department thesis project studying the effectiveness of soil solarization in Pacific Northwest nurseries. Soil Solarization required a tilled row of soil to be tightly wrapped in clear plastic sheeting. The clear plastic would use the greenhouse effect to super heat the soil, killing soil pathogens and weed seeds. During the three year project, I installed over 600 soil sensors for monitoring soil moisture and temperature movement under the plastic treatments, while other departments assessed the mortality to the weeds and pathogens. At the end of my thesis work, I had produced a model for predicting weed seed mortality from solarization.
Upon completion of grad school, I went into extension where my passion for science communication was used in combination with my knowledge of technology in horticulture. I have been working for OSU at the North Willamette Research and Extension Center since 2019. In the Nackley Lab as a Faculty Research Assistant I set up experiments that explore greenhouse and nursery production. Current projects include: flying UAV’s with near red spectrum cameras to look for plant stress from the sky, VWC sensor base irrigation of shade trees and lysimeter controlled irrigation for indoor hemp production. I am also part of OSU’s Intelligent Spray Project where an air-blast sprayer that has been retrofitted with a LiDAR system is evaluated for efficacy and pesticide savings in the nursery industry. My favorite part of doing research is setting up a new experiment in a way that will hopefully show differences in plant growth based on different treatments. The challenge of working with Mother Nature while manipulating the factors of plant growth fascinates me, especially when there are visual growth differences attributable to the experiment’s set up. These days I can be found either fiddling with technology, setting up overly complicated irrigation systems or at a podium giving talks about what information has been gained from the results of my trials. Where ever you do find me, you can be sure I am on a passionate course for understanding the whys behind growing plants.
How we are using low-cost and open-source weather stations for decision support
On-farm weather data can provide valuable information to growers including informing irrigation scheduling, tracking plant growth indices, and mitigating damaging events like frost, heat waves or disease. Weather can vary widely across landscapes, even across a single field, and we have found that there is value in having multiple distributed weather stations on-farm to capture variability across small spatial scales. To do this cost effectively, I developed a low-cost open-source weather station (LOCOS) for my M.S. thesis at the University of Idaho that uses low-cost sensors and an Arduino microcontroller for data logging. By distributing multiple LOCOS across a vineyard, we found that there were distinct micro-climates that had varying susceptibility to grape powdery mildew disease. From calculating a Powdery Mildew Risk Index at each station, we saw that some vineyard blocks could benefit from unique fungicide application schedules. You can read more about this project here.
Since then, the LOCOS have been adapted to study crop water stress. In the summer of 2021, we used LOCOS equipped with infrared thermometers to develop a crop water stress index (CWSI) for hazelnuts. The CWSI is based on leaf temperature and weather data (air temperature, relative humidity, wind speed, and solar radiation). Leaf temperature is a known indicator of plant stress. When a plant is actively transpiring the leaves will be cooler than the surrounding air because of the evaporative cooling effect of transpiration. Whereas a plant that is stressed and not transpiring will have a warmer canopy that is closer to the ambient air temperature. The CWSI varies from 0 to 1, where 1 indicates a stressed, non-transpiring plant, and 0 indicates a well-watered plant transpiring at max potential.
We used the LOCOS to collect canopy temperature of the hazelnut trees from June to September, 2021. The trees were subject to three different irrigation treatments, over watered, moderate water, and no water (dryland) so we could get a range of canopy temperatures to incorporate into our model. We also collected data on leaf water potential, leaf transpiration and leaf conductance to validate the index against. We found that the CWSI we developed was closely correlated with leaf water potential (r2 = 0.84), leaf conductance (r2 = 0.75) and leaf transpiration (r2 = 0.72). These are exciting results because it shows that the LOCOS could provide continuous data on crop water stress that can be used to inform irrigation decision in near real-time. This summer, we will use the LOCOS in another study to develop a CWSI for red maples.