Michael Santiago,* Alan Lakso, and Abraham Stroock
*FloraPulse Co, 91 Lyle Way, Davis, CA 95618 (michael@florapulse.com)

Vine water status determines vine growth, productivity, fruit composition, and terroir; therefore, it is important to accurately measure and control water stress. The pressure chamber is the accepted method to measure water stress, but this instrument requires an operator and can only provide limited spot data. Other instruments like soil tensiometers, capacitive sensors, or dendrometers only measure water stress tangentially and suffer from a lack of accuracy. We present on our progress in developing a microtensiometer implant to directly and continuously measure stem water potential in grapevine. The microtensiometer is a miniaturized, 5 mm × 5 mm tensiometer built through microfabrication techniques. Microtensiometer probes were embedded in the main trunk of Merlot grapevines and recorded data from Sept 2017 to Feb 2018. The sensors measured the diurnal pattern of water potential, including both predawn and midday water potential, with values ranging from -3 bars to -15 bars. Sensor measurements agreed with pressure chamber readings taken over the course of two months. The sensors continued taking readings throughout the winter during vine dormancy and measured a smaller diurnal pattern during this time. Work is underway to understand how this unprecedented higher-resolution data may be useful. These results indicate that the microtensiometer implant could be a viable alternative to the pressure chamber. Here we will further present on our latest results in testing the microtensiometer at multiple vineyards during the 2018 growing season.

Funding Support: National Science Foundation USDA