This dataset consists of mid-infrared (MIR) spectra measured on 427 archived soil samples from arable and grassland habitats across Great Britain in 2007. Data on diffuse reflectance spectra were obtained from subsamples of finely ground soil, recorded as absorbance values for wavenumber range 4000-400 cm-1. The soil samples were collected as part of the Countryside Survey monitoring programme, a unique study or 'audit' of the natural resources of the UK's countryside. The analyses were conducted as part of study aiming to quantify how soil quality indicators change across a gradient of agricultural land management and to identify conditions that determine the ability of different soils to resist and recover from perturbations. Full details about this dataset can be found at https://doi.org/10.5285/d66ca0a6-403d-4f5a-bef1-8ee177f1e1b3