Soil water potential can be used as a proxy for plant available water in irrigation scheduling. This study investigated the relationship between soil water potential and plant water status of pines planted into two different substrates. Predawn leaf water potential as a well-established measure of the plant water status and soil water potential correlated very well.
However, estimating the plant water status from individual sensor readings is subject to significant estimation errors. Furthermore, it was shown that heterogeneous soil/root ball combinations can lead to critical effects on the soil water balance and that sensors installed outside of the root balls cannot estimate the plant water status without site-specific calibration.
Hertzler, J. and Rust, S., 2021. Soil Moisture as Predictor of Plant Water Status. Arboriculture & Urban Forestry, 47 (3), 110–115.