This document reviews the use of visible and infrared spectroscopy to predict soil organic matter content and quality from soil spectra. It discusses techniques like visible/near infrared, mid infrared spectroscopy and various preprocessing, calibration and validation methods. Least squares support vector machines calibration is recommended as it balances accuracy and generalization. Factors like scale of calibration, accuracy and uncertainties are also covered. The document concludes more robust calibrations are possible with standardization and global spectral libraries, and outlines areas for future work.