Construction of a Moisture Sensor for Smart Irrigation and Determining the Proper Location for Installation to Stop Irrigation to Prevent Water Loss

Due to the issue of water scarcity and drought in Iran, agriculture water management is essential. Agriculture water management requires a policy of correct and efficient use of water, and the smart irrigation system is a suitable and optimal way to use water properly. For this purpose, a moisture sensor device was designed and constructed in February and March 2019 to determine the appropriate time to stop irrigation in furrow irrigation. Testing the device in the laboratory and its application in the Farm of the Campus of Agriculture and Natural Resources, University of Tehran, (Mohammad Shahr), Iran, from April to July 2019. The purpose of this study was to evaluate the performance of smart sensor of soil moisture to determine the optimum depth of installation and recording of soil moisture at 10, 30 and 50 cm depths and different length ratios in furrow irrigation. Initially, calibration of the device was carried out on field soil and based on the obtained validation, the device was transferred to the field. To achieve the goals of optimum depth of installation and optimum length, 36-meter furrows with a distance of 0.75 meters were created in the field. Sensitive lengths in furrows with 0.5L, 0.75L, and 0.85L ratios were selected as the starting points. The results showed that in the calibration and validation phase the R2 value (coefficient of determination) were 0.93 and 0.95, respectively, and in the calibration and validation stage the value of NRMSE (Normal Root Mean Square Error) was 80 and 13.81%, that indicating good model training in the calibration stage. Also, the average RE (Relative Error) parameter in estimating soil moisture was 2.74%, indicating high accuracy of the device in estimating soil moisture. The results also showed that if the device was installed at a depth of 30 cm from the soil surface of the furrow and at 75% from the beginning of the field, the depth and runoff losses would be minimal and irrigation adequacy would be best compared to other depths and lengths. It is expected that with optimal water consumption and timely interruption of irrigation, deep losses and runoff will be avoided and with low water consumption, the productivity of crops will increase.