The Research Behind Dendrometer Use

Phytech dendrometer on a pear tree.

At the heart of Phytech’s platform is the dendrometer, a research tool used since the 1950s to track changes in stem or trunk diameter. The concept is simple, but powerful. The maximum daily shrinkage (MDS) of a tree can indicate when the plant is experiencing stress, well before it’s visible in the canopy.

While dendrometers are not new, Phytech has revolutionized their use. We collect continuous, high-resolution data and run it through variety-specific, phenology-aware algorithms, turning trunk dynamics into clear, actionable “Plant Status” signals.

One key innovation is how we benchmark individual tree growth, not just stress, against thousands of other growers with the same crop, variety, and growth stage. 

Unlike MDS, which reflects water stress, growth is a more intuitive parameter because it directly represents tree productivity. These benchmark lines give you a clearer picture of what to expect. They can reveal signs of chronic stress, hint at fruit load, and highlight whether your trees are falling behind compared to others in similar conditions. The goal is to offer feedback that is operationally useful.

The Science Behind the Dendrometer System

Over the years, Phytech has been involved in several academic and on-farm validation efforts. Two recent studies offer clear insight into how trunk dynamics connect to plant health and productivity:

1. Understanding Deficit Stress in Almonds

In a multi-year study co-authored by Phytech’s Head of Agronomic Research, Ido Gardi, researchers compared full (1300 mm) and deficit (600 mm) irrigation in almonds to shed light on how chronic water stress impacts tree physiology and long-term yield. 

When almond trees didn’t get enough water, they showed signs of stress at the physiological level. Their stem water potential dropped below –2 MPa, and they partially closed their stomata, limiting how much carbon dioxide they could take in. As a result, their ability to photosynthesize was reduced to about 14 µmol m²/s. 

At first, the trees tried to keep growing by using stored water and energy, but over time, this drained their internal reserves. By the second year, the long-term stress led to a 35% drop in yield, showing just how costly under-irrigation can be for growers.

This is where Phytech’s dendrometers offer a key advantage. The study found that integrating soil moisture data with trunk growth measurements (specifically, the rate of trunk expansion or contraction) provided one of the most reliable indicators of whether trees were adequately irrigated. 

The study also suggests that adaptive irrigation strategies that align with the tree’s phenological stage and real-time stress status can help optimize both water use and yield. Phytech enables this level of precision by continuously monitoring plant and soil data, helping growers avoid both over- and under-irrigation. 

2. Linking Soil Dynamics to Tree Transpiration

A second study, also co-authored by Ido, focuses on how different irrigation volumes (600, 900, and 1250 mm) affected almond tree transpiration and root behavior. By modeling soil drying between irrigations, the researchers were able to predict stress thresholds before yield was impacted. 

What they found was that 600 mm irrigation caused soil water potential to drop to -1 MPa, restricting transpiration. Surprisingly, trees adapted by growing deeper roots to tap winter reserves, showing resilience, but still under clear water stress. 1250 mm irrigation offered no added benefit and even risked overwatering sensitive rootstocks. A 900 mm irrigation regime was “just right,” consistently supporting maximum transpiration and yield. 

The study also introduced a model that can predict when soil moisture will drop low enough to reduce tree transpiration. This is important because trees start to slow down their water use before they show visible signs of stress. By monitoring soil moisture and understanding how it affects water uptake, growers can schedule irrigation more precisely.

Irrigation planning using soil probes remains a common and trusted practice, largely because soil conditions tend to be stable and predictable throughout the season. However, the challenge lies in determining the appropriate thresholds for action. There are many ways to set these limits, but most rely on fixed assumptions about soil properties and plant behavior.

Phytech enhances this approach by layering plant sensing and stress monitoring data on top of traditional soil moisture readings. This added context helps scale and interpret the soil data more accurately. The result is a more intuitive and precise framework for irrigation planning that adjusts as crop conditions change.

Phytech dendrometer attached to a vine trunk.

Let the Plant Lead

The dendrometer might not be new, but Phytech’s application of it is changing how growers make decisions. By combining field-proven plant physiology with modern algorithms and benchmarked insights, we turn every trunk into a trusted advisor.

Because your trees may not speak, but they’re always telling you something. With Phytech, you’ll know exactly what they need, before stress becomes a problem.

Let science back up your irrigation plan. 

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