Using Infrared Technology to Detect Soil Moisture Level

Accurate and rapid measurement of soil moisture is vital for some agricultural applications. The development of various measurement methods with different advantages has been ongoing for years to determine soil moisture. The direct measurement method is based on weight change and gives the most accurate result, but it requires a long time and labour. In indirect methods, soil moisture is generally estimated by using different soil properties such as soil electrical conductivity, electrical resistance change and radioactive reactions in the soil. Indirect methods needs complex calculation and calibration processes and additional analysis. In this study, the possibility of using infrared technology as an alternative to the conventional measurement method based on gravimetric measures was investigated to define soil moisture. The success of the developed technique was tested by comparing the conventional measurements on the soil samples with eight different moisture content. Three different radiation intensities (IR) (2358 W m-2, 3165 W m-2 and 4187 W m-2) were used for soil drying. Variance analyses, multiple comparisons and MAPE (mean absolute percentage error) values were used to determine the differences between infrared and conventional methods. It was determined that the difference between the conventional and infrared methods for all power levels was not statistically significant. The correlation coefficients between moisture values of the conventional and infrared were determined as 0.966, 0.964 and 0.979 at given IR levels; respectively. For all experiments, the correlation coefficient was defined as 0.979. Although the lowest MAPE values were determined using 4187 W m-2 of IR, there was no statistical difference between the MAPE values of IR levels. The time requirement in the conventional method is at least about 24 hours. It was decreased to 34.75 minutes with IR technique. The IR technique yielded very fast and correct results and there was no need for complex calibration procedures.