Determination of organic matter mineralization in compost amended soils using FT-NIR spectroscopy

Abstract

This study is aimed at developing a non-destructive method for determining organic matter mineralization using FT-NIR (Fourier Transform-Near Infrared) spectroscopy. Soils with two different textures were mixed with olive solid waste (OSW), OSW composts and nitrogen, phosphorus and potassium (NPK) fertilizer. Samples have been incubated at 25 oC for 9 months. After this period, some chemical and physical analyses were performed on the samples using standard methods. Also reflectance spectra of the same samples were acquired right after the standard measurements using FT-NIR spectroscopy. Calibration models between the standard measurements and the spectral measurements performed on samples were established applying Partial Least Squares (PLS) method. Promising N prediction was obtained for the compost added soil group (R2=0.62 and RMSECV=0.05) and good N prediction was performed for the control soil group (0.93 and RMSECV=0.01). C was predicted successfully for almost all of the data groups. Prediction of C for the data group that included all the soil groups was performed with a coefficient of determination of 0.88 (RMSECV=0.27) in validation. C was predicted with the coefficient of determination of 0.93 (RMSECV=0.23) for the compost added soil group. It was shown with this study that NIR spectroscopy has the potential of sensing soil contents non-destructively.