By Nella Mae Parks
Originally published in Growing for Market Magazine on April 1, 2023.
Last summer, I joined with four other farms in the high desert of Oregon to do field research on irrigation management in no/low-till small-scale vegetable production. The project lead, Katie Swanson of Sweet Union Farm in Klamath Falls, Oregon, invited each farm to measure differences over one growing season in plant-available water between beds with no or low-till preparation and beds prepared with tillage.
Through funding from a USDA Sustainable Agriculture Research and Education (SARE) grant each farm received tensiometers, weather stations, and technical assistance from folks at Oregon State University (OSU.) Our SARE grant was focused on understanding and improving our water conservation practices and decision making through low/no till and soil water monitoring. We were able to really test whether no/low till improves water holding capacity and identify changes we could make to improve water conservation in our dry climate.
This video provides an overview of the project. Read on for deeper insights into the farmers' key takeaways. Video credit: Produced and edited by Kristin Pool Productions.
Growing in the High Desert
While Oregon is known for its dense forests and rain, this “westside” environment only covers about one third of the state. All the country east of the Cascade mountains looks more like the neighboring states of Nevada or Idaho rather than rainy coastal Oregon.
High desert weather is defined by extreme daily temperature swings (40F to 100F), daily afternoon wind, late frost (in June), early frost (in August), a short spring (2-3 weks) and very little precipitation (10 to 16 inches per year.)
As SARE participant Caleb Thompson of Sungrounded Farm put it, “we receive 11 inches of precipitation annually, which predominantly comes in the form of snowfall in the winter.” High desert farmers are reliant on snow as our reservoir and snowmelt as our summer irrigation water. If there is little snow in the winter or it melts off too fast, we can face water shortages. Several of the participant farms are facing a chance of no water allotment from their ditch system this summer (literally zero!), which makes last year’s water conservation research even
“Farmers like us in extreme climates are constantly adapting. With climate change, other places will face what we face every day, and I think we have a lot to share.” - Katie Swanson, Sweet Union Farm (shown right)
Soil moisture is affected by a matrix of factors, some of which we live with and others which we try to influence:
Soil physical properties (texture and organic matter)
Precipitation and irrigation
Evaporation from surface
Temperature, humidity, and wind
Evapotranspiration from plants
Temperature, humidity, and wind
Plant type and maturity
With tunnels and shade cloth we can modify a few of these soil moisture factors such as temperature, humidity, and the drying influence of wind. Through increasing organic matter, mulching, and tillage practices, we can increase (or decrease) the water holding capacity. While the farms in the cohort have tried to maximize soil moisture in these ways, what we were missing was monitoring and understanding of the resulting soil moisture. We didn’t have the data to show the impact of these practices or to know when and how much water the soil and
plants really needed.
SARE Case Study Set Up
Each farm buried three Watermark tensiometers in each of the three test beds at three different depths. Tensiometers measure how easy it is for a plant to suck water from the surrounding soil. A lower centibar reading means water is easily available; a higher reading means the soil is drier; zero means the soil is saturated.
We monitored soil water tension weekly throughout the season and kept track of irrigation events. OSU staff monitored temperature, humidity, precipitation, and wind through our on-farm weather stations.
Each of the five farms chose a crop to test with no-till, low-till, and tillage practices. We each wanted to understand tillage and water needs of specific crops.
Sweet Union Farm, Klamath Falls, Oregon tested paste tomatoes.
Fibonacci Farm, Bend, Oregon tested zinnias.
Sungrounded Farm, Terrebonne, Oregon tested onions.
Sakari Farm, Tumalo, Oregon tested golden beets.
Nella Mae’s Farm, Cove, Oregon tested lettuce mix.
Left to right: Sweet Union Farm; Fibonacci Farm; Sakari Farm; Nella Mae's Farm.
While Katie at Sweet Union wanted to know how far she could push paste tomatoes in each test bed without watering, I wanted to understand if the tillage methods influenced soil moisture, and therefore, direct-seeded lettuce germination and production in July and August. While we were testing different crops and had different questions, the commonality was how well the soil held water given different tillage regimes.
Case Study Takeaways
1. Less tillage did improve soil water holding capacity and crop performance on several farms.
This was a small case study, so conclusions we can draw are limited. However, two farms in the cohort saw that beds with less tillage saw better soil moisture and required less irrigation.
For the rest of us, the results were mixed. However, our observations of the no/low till beds, germination, and production results anecdotally encouraged us to keep monitoring soil water moisture between tillage treatments. For example, my low-till lettuce beds out-performed my tilled lettuce beds in terms of germination and fewer weeds. My broadforked lettuce bed outperformed my tilthed and tilled beds so much that I was motivated to broadfork all beds this year. For others crop performance seemed similar between tillage treatments, which is a good argument for not tilling. If it tillage doesn’t improve crop performance, why waste time and gasoline on it?
2. New tools improved irrigation efficiency.
Perhaps the most impactful thing we learned from the SARE project was the value of monitoring soil moisture and using tensiometers.
Both Katie and I feel silly saying it, but sometimes it was kind of a pain to spend five minutes checking soil moisture. It isn’t hard, but there are just so many demands on the farm that this simple monitoring practice sometimes fell to the bottom of the list.
However, being a part of a cohort of farms and a case study project motivated us to do the work. At the end of the season, we were able to really see the results. During the season the data we collected gave us a sense of what was going on below the soil surface and allowed us to more confidently wait to irrigate and/or cut back on water. If you know there is water available in the rooting zone of your tomatoes, you can sleep at night without adding more.
Sam Schreiner at Sakari farm also said the tensiometers will help him give better instructions to employees. The “stick your finger in the soil test” is subjective and you can’t stick your finger down two feet. But you can tell employees, “check the tensiometer and water when you get to 30 centibars.”
Caleb Thompson at Sungrounded Farm [shown left] said soil moisture data will help to prioritize watering. In the high desert when you may only get water for one day per week, tensiometers help farmers understand which fields or crops need water rather than just broadcasting one inch over the whole farm.
3. Better data make more contentious farmers.
Without monitoring, it is easy to irrigate on a schedule or based on assumptions rather than the in-the-soil reality. It is easier to water every crop on the same schedule and repeat the watering regime year after year.
Each farm said that the practice of monitoring made us more contentious and observant through the season. The farms with limited water were able to waste less where it wasn’t needed.
I felt more accountable to water conservation. Unlike the others in the cohort, I use well water and have pretty good access to water. Checking the tensiometer and finding I had overwatered made me dial back the amount and duration of irrigation, which is better for the soil, the crop, and for our aquifer.
SARE Program Takeaways
The design of this SARE study by project lead Katie Swanson and OSU Small Farms agent Maud Powell made it easy for farmers to participate.
Farmers were paid for their time and compost (about $1,700.)
The case study approach was adaptable to each farm.
No-till / low-till / tilled treatments were defined by each farmer.
Water tension sensors and weather stations were provided, and set up help was available.
Data analysis was performed by staff at OSU.
Working with an agricultural technical service provider made our grant application and project more successful. Maud Powell at OSU Small Farms was able to help narrow down ideas for the grant proposal and create a cohesive project.
Creating a cohort of farms made our project more impactful and more likely to get funding.
SARE grants can help with farmer behavior change. Paying and supporting farmers through this grant encouraged us to adopt new tools/technology and to spend time monitoring. The grant, cohort, and OSU staff gave us accountability to collect data and support in analyzing it.
The results of the case study reached a larger audience through connections to other organizations who were excited about our ideas.
What makes the high desert country tough to grow in is a combination of extreme weather, changing climate, and the bad water policy and systems we’ve inherited. However, this cohort of farmers used the SARE grant opportunity to tune into water conservation and tune up our irrigation management skills. As project lead Katie Swanson put it, “farmers like us in extreme climates are constantly adapting. With climate change, other places will face what we face every day, and I think we have a lot to share.”
Spring Alaska Shreiner on Sakari Farm