[This dataset is embargoed until June 30, 2026]. The dataset contains information about the visible and near-infrared (Vis-NIR) reflectance spectra collected from re-quartered reserved fine earth (FE) soil samples obtained during the 2018-2019 Countryside Survey. Out of the 481 samples collected during the survey, only 451 were used for diffuse reflectance spectroscopy due to sample availability. Diffuse reflectance spectra were gathered from 451 samples using the ASD AgricSpec spectrometer and from 306 samples using the FOSS DS2500 spectrometer in the visible (350 to 780 nm) and near-infrared (780 to 2500 nm) regions, with spectral resolutions of 1 nm and 0.5 nm, respectively. The spectral data from both instruments were employed to predict 23 soil parameters related to harmonized soil properties within the Open Spectra Soil Library (OSSL) prediction engine. A comparative analysis was performed between 12 of the available measured soil matrices and their corresponding prediction results Full details about this dataset can be found at https://doi.org/10.5285/ea727f8d-6441-4d88-8ed7-1760bda0c3c3