Developing the right metric for dry matter is vital in defining measurable parameters related to biochemical properties that define root yield and root quality. In this SOP, the procedure for production of definitive spectra that defines the connection between the spectra acquired from grated cassava fresh root and the dry matter content is described. The procedures describe the scanning and spectral acquisition of fresh root cassava spectra using the FOSS DS2500 NIRS equipment. Cassava samples are harvested from labelled fields using appropriate harvesting tools and prepared by peeling and grating using a laboratory grater. The grated material is placed on a sample plate with accompanying barcode and moved to NIRS equipment. This is followed loading the grates into a sample cup and scanning of the grated material filled in the sample cup. The procedure is repeated by loading fresh material from the main sample into the sample cup producing two subsets of scans from one particular accession. Spectral data produced from these scans is downloaded and further processed for use in calibration development while it is also uploaded on cassava base as an additional file. Reference data generation is carried out by approved reference methods in repeatability analyses carried out at NaCRRI. Critical points of consideration include the development and maintenance of correct labelling.