Journal Article

Establishing the Zone of Interference for Substrate Moisture Sensors in Three Soilless Substrate Components

Wright, Wesley C., Krauss, Carolyn, Sun, Xiaocun, Eady, Erica, Owen, James S., Fulcher, Amy

2026

Overview

Water and soilless substrates are critical resources to the nursery industry. Researchers and nursery growers are increasingly using substrate moisture sensors (SMSs) to investigate soilless substrate water retention and hydrology in container production systems and to schedule irrigation to optimize the use of these resources. Research explored the influence of proximity of two EC-5 dielectric constant SMSs positioned in four different orientations on volumetric water content (VWC) measurement. One SMS remained stationary throughout each test and the other, the mobile SMS, was repositioned to create the change in distance between the two SMSs. Both SMSs were installed in coir, Sphagnum peat moss (peat), or pine bark, and one was designated the mobile SMS. The mobile SMS was removed and reinstalled in 1-cm increments closer to the stationary SMS while the VWC of the stationary SMS was recorded. For coir and pine bark, there was no effect of SMS proximity for any orientation ( P ≥ 0.080) even when the SMSs were touching. For peat, when the orientation was positive-to-negative or positive-to-positive, the mobile SMS had a higher VWC than the stationary SMS ( P < 0.000). The mobile SMS had a more negative linear relationship between distance and VWC than the stationary SMS ( P = 0.001); however, this effect was within the EC-5’s accuracy of 0.02–0.03 cm 3 ·cm −3 . Theories for this effect, including the known compressible nature of peat and the established pattern of peat degradation from physical handling, were explored.