California Crop Stress Index

SWP (Stem Water Potential) measures how hard a tree is working to pull water from the soil. It's measured in bars of negative pressure. More negative = more stress.

Stress thresholds vary by crop. Almonds typically trigger irrigation around -12 to -14 bar, while wine grapes can handle -14 to -16 bar depending on the growth stage and deficit strategy. What matters most is the trend — is stress increasing, stable, or decreasing week over week?

As a general guide: readings near -3 to -6 bar indicate low stress (well-watered), -10 to -14 bar moderate stress (irrigation timing matters), and beyond -16 bar high stress where yield impact is likely.

Why this is different from satellite or ET-based tools: Weather models and satellite imagery estimate what plants should need based on air temperature, humidity, and canopy reflectance. FloraPulse microtensiometers measure what the plant is actually experiencing — the real hydraulic pressure inside the trunk. Two orchards with identical weather can show very different stress because of soil type, rootstock, tree age, and irrigation system efficiency. Direct measurement catches what models miss. Learn more.