How do I position my substrate probe in a large no-till or living-soil bed?

Probe placement is key to getting reliable moisture and pore-water EC (PWeC) data.

In large no-till or living-soil beds (12–24″ / 30–60 cm tall), vertical and horizontal positioning make a big difference.

Best single-sensor placement

Place the probe 25–35% of the bed height below the soil surface. This corresponds to roughly:

• 4″ / 10 cm deep in a 12″ (30 cm) bed

• 5–6″ / 13–15 cm deep in an 18″ (45 cm) bed

• 6–8″ / 15–20 cm deep in a 24″ (60 cm) bed

This depth represents the active root zone, where the plant takes up most of its water and nutrients.

It’s ideal for monitoring crop steering, drybacks, and irrigation timing.

Two-sensor placement (recommended)

Soon, the Grow Sensor PRO will support up to 2 substrate sensors per unit (28/10/25).

If your bed allows for two sensors, you’ll get the most complete picture by tracking both the upper and lower moisture zones:

• Upper sensor (plant-active): 25–35% of the bed height below the surface → Used for crop steering and monitoring drybacks.

• Lower sensor (drain/leach): 3–4″ (8–10 cm) above the bed bottom → Used to track salt build-up and leaching near the base of the bed.

Even in taller containers, placing the lower probe 3–4″ from the bottom keeps it just above the saturated zone, which forms at a similar height across most soil mixes.

Horizontal position

• Place the probe halfway between plants and between emitters, within the main wetted zone but not directly under a dripper.

• Stay at least 4–6″ (10–15 cm) away from the bed’s fabric sidewalls to avoid edge drying that can skew readings.

Orientation

• Insert the probe with the prongs parallel to the soil surface, level and fully buried.

• Ensure firm contact with the soil — no air gaps.

• Measure depth from the mineral soil surface, not from the top of any mulch layer.