Soil Moisture Sensor Irrigation Controllers Response to Different Temperatures and Salinities

摘要

Soil moisture sensor systems (SMSs) have demonstrated that can reduce irrigation application in Florida. However, SMSs have not been tested under Florida soils, irrigated with reclaimed water, which contains salts that can affect the measured soil water content (SWC). The objective of this research was to test different commercially available SMSs under controlled conditions, and analyze their responses under different levels of water salinity and temperature. Three brands/models were selected for this experiment: Acclima/SCX, BaselineAA/aterTec S100, and Dynamax/IL200-MC. Containers filled with a sandy soil were manufactured so that they could be saturated from the bottom to minimize entrapped air and fitted with sintered metal filters to allow vacuum application for water removal in a timely manner. The containers were installed in a controlled-temperature chamber and were saturated and dried down across three temperatures (10, 25, and 35°C) and three electrical conductivities (0.0, 0.7, and 5.0dS/m). Each container was placed on a platform-scale to determine soil-water loses, by weight variation over time. The scale readings were compared to the SMS readings, and calibration curves were developed through regression analysis. Preliminary outcomes show that most replications resulted in linear regressions with R2 values higher than 0.94, indicating that all the units tested had a high precision for measuring the SWC, but calibration is necessary to achieve accurate readings. Increasing the temperature from 25°C to 35°C and/or the salinity from 0.0 to 0.7 dS/m neither affect the accuracy nor the precision of the different SMS systems, when SWC values below 15% were considered.