Are you questioning the readings of the soil moisture sensors? Cleaning the probes could improve the accuracy of the measurements.
Metergroup advises cleaning each probe using mild liquid dish soap (without lotions/moisturizers) and a nonabrasive sponge or cloth. Afterwards, rinse the sensor and probes with tap or deionized water thoroughly.
Do not touch the needles with an ungloved hand or bring them in contact with any source of oil or other nonconducting residues.
For more information, please click here for the knowledge base from Metergroup.