Methods to correct temperature-induced changes of soil moisture sensors to improve accuracy

Area of Science:

• Soil Science
• Agricultural Engineering
• Environmental Monitoring

Background:

• Accurate soil moisture measurement is essential for precision irrigation, but sensor performance can be affected by temperature variations.
• Understanding sensor response to temperature gradients is crucial for reliable volumetric water content (VWC) data.

Purpose of the Study:

• To assess the performance of soil moisture sensors (Teros-12, 10-HS, SoilWatch-10) across a temperature gradient (4°C to 14°C) in sandy soil.
• To evaluate the necessity and effectiveness of temperature correction for improving sensor accuracy.

Main Methods:

• Soil moisture was stabilized while temperature was gradually increased.
• The change in volumetric water content (ΔVWC) was measured for each temperature increment.
• Observed (Oθ) and temperature-corrected (TCθ) VWC were compared using regression analysis and statistical metrics (RMSE, IA, MBE).

Main Results:

• Teros-12 and 10-HS sensors showed a linear decreasing trend in ΔVWC with increasing temperature, while SoilWatch-10 exhibited an increasing trend.
• The 10-HS sensor demonstrated the highest accuracy (RMSE = 0.011 cm³/cm³), followed by Teros-12 (RMSE = 0.015 cm³/cm³).
• Teros-12 and 10-HS sensors slightly underestimated VWC (MBE = -0.014 and -0.011), whereas SoilWatch-10 overestimated it (MBE = 0.028).

Conclusions:

• Temperature correction is crucial for enhancing the accuracy of soil moisture sensors, minimizing over/underestimation.
• The 10-HS sensor provided the most accurate measurements, followed closely by the Teros-12 sensor.
• All tested sensors showed strong agreement (IA = 0.99) between observed and temperature-corrected VWC, indicating their reliability when corrected.