Final Report – Funding Cycle 2022-2025 – Three years
Principal Investigator: Pete Jacoby, Washington State University, Pullman
Summary: The objective of this project was to evaluate the combined use of two types of soil water sensors for enhancing irrigation efficiency. Irrigation amount and frequency of application was monitored through recorded measurements of soil water content and soil water tension to learn the potential to achieve and maintain a consistent level of water stress on the grapevine under deficit irrigation. Findings would confirm the ability for using sensors to control irrigation scheduling to achieve water savings while maintaining goals for grape yield and quality.
Data was collected from two sites, one in Red Mountain AVA and in Walla Walla Valley AVA, both of which were instrumented with soil water content sensors and soil tenisometers. Soil moisture data was recorded for three growing seasons and grape samples collected from treatments were weighed for yield estimates and analyzed for quality attributes.
While this research will progress under a supported grant from the Northwest Center for Small Fruits Research, results to date indicate that:
- Soil water content sensors that are contained within a probe and are capable of measuring to a depth of two to three feet can be used to drive automated irrigation.
- Use of a soil water tensiometer can provide additional verification of soil water status by indicating when vines cannot extract soil water and additional vine stress will occur.
- Both soil water content and water tension status will vary according to soil type and can be predictive of the onset and duration of vine water status.
A new stem water potential sensor is under evaluation as part of this project. The FloraPulse sensor was installed in July 2025 on 18-year old vines to provide an indication of stem water potential differences between vines irrigated by surface drip and subsurface drip irrigation. These sensors are producing a continuous record of stem water potential in real-time and reveal significant levels of diurnal change in stem water stress.
Download the report above.