Hyperspectral response and monitoring study of soil moisture content based on the optimized spectral index

Soil moisture controls the exchange of energy between the land surface and the atmosphere and significantly affects plant growth and productivity. Hyperspectral (350-2500 nm) monitoring of soil moisture content (SMC) could provide a theoretical basis for the real-time estimation of spatial and temporal variations in soil moisture. During this study, we have developed SMC prediction models in different soil moisture ranges by using the combination of spectral preprocessing methods and optimized spectral indices. Results indicated that first-order derivative (FD) preprocessing method can highlight the effective information of the spectra and improve the correlation between spectral reflectance and SMC. The spectral reflectance exhibited a strong correlation with SMC near 1400, 1700, 1900, and 2200 nm. The FD-NDSI-W0-model had the best SMC prediction and applicability (R-2 = 0.977, root mean square error = 3.413%, relative percent deviation = 6.171) to predict SMCs. Overall, pretreatment methods, combined with the two-band random combination to optimize the spectral index to build a prediction model of SMC, could be applied for accurate monitoring of SMC.