Investigation the Performance of Smart Sensors as a New Approach to Determine Soil Moisture Content

Accurate estimation of soil water content is necessary for effective irrigation scheduling. Different methods are used to determine the soil water content in which the speed and accuracy of the measurement by these methods are important. In recent years, smart sensors has been introduced as a fast and accurate method in order to estimate soil moisture content. In this study, the performance of 4 smart sensors as the fast method were compared with several conventional methods in order to estimate soil moisture content at 30 and 60 cm depth from soil surface in a micro irrigation system. The smart sensors used in this study were Watermark 200ss-v, Watermark 200ss, ICS9001 and ICS 9101 and the conventional methods used were tensiometer, gypsum blocks, neutron meter and gravimetric method. Results indicated that all smart sensors used in this research except of ICS 9101 were acceptable device for estimating the soil moisture content at 30 and 60 cm depths from the soil surface. The relative root mean square error (RRMSE) for the sensors of Watermark 200ss-v, Watermark 200ss, ICS 9001 and ICS9101 were 13, 11, 16 and 23% and the coefficient of correlation R2 values were 0.79, 0.84, 0.73 and 0.55, respectively. Furthermore, among the conventional methods, the neutron meter also showed a reasonable accuracy while the equitable accuracy were not observed in gypsum blocks and tensiometer. Results showed that the performance of Watermark 200ss-v, Watermark 200ss and tensiometer for measuring the soil moisture under low soil moisture tension is better than in high soil tension condition.