Zirconia Coatings as Efficient Soil Moisture Sensors for Water Irrigation

In agriculture sector, a soil moisture sensor plays a vital role in controlling the irrigation through the adequate and timely moisture of soil essential for the crop production. Owing to the chemically inert nature of zirconia, it is found to be a good material for soil moisture sensing. Therefore, the present study reports the synthesis of sol-gel based zirconia coatings and their application as efficient soil moisture sensor for water irrigation. For this purpose, zirconia was coated on 316L stainless steel substrate using zirconium propoxide precursor through sol-gel process and spin coating technique. The obtained zirconia coatings were used to fabricate and study the zirconia soil moisture sensors. Zirconia sensors were fabricated using zirconia coatings synthesized from various concentrations of zirconium precursor. The chemical structure and crystalline nature of zirconia coatings were analyzed using FTIR spectroscopy and X- ray diffractometer. Moreover, the contact angle and roughness of these coatings have been measured. It is observed that the contact angles and roughness of the synthesized zirconia coatings increased with increase in the precursor concentrations. All zirconia coatings manifested the tetragonal crystal structure. The resistance of the zirconia soil moisture sensors was measured for different moisture content in soil (%). The zirconia sensors are tested in an active black soil moisture condition and their resistances changed for the soil moisture range of 20 to 50%. Further, zirconia soil moisture sensor monitoring system was developed using NImyDAQ and LabVIEW which is useful for the water irrigation.