Estimate of soil Cation Exchange Capacity using reflectance spectrometry

CEC is the most important soil engineering properties used to determine the swelling potential of soil. Measuring CEC of soil is difficult, time-consuming, costly and consuming of dangerous chemical materials. In this study the ability of spectral reflectance to estimate the amount of CEC were investigated. So 45 soil samples were collected from Namkhaneh series of Kheyrood kenar Forest and their reflectance were measured in the range 350-2500 nm in dark room. Then the relationship between CEC and reflectance and first derivative of reflectance were analyzed by single band Pearson correlation, PLSR and two groups of narrowband soil indices (RI, DI). The results of this study showed that narrowband indices have stronger relationship than PLSR and the DI index in case first derivative have highest correlation (R2=0.82, RMSE=5.01). In the PLSR method between reflectance and CEC strong relationship was observed while the indices of first derivation reflectance and CEC have stronger relationship than row reflectance. So reflectance can be as a nondestructive, fast, easy and Cost effective method to estimate the CEC.