<p>Soil organic carbon (SOC) constitutes the largest terrestrial carbon stock. Both distribution and variation of SOC stocks are needed to constitute reference baseline for studies on temporal SOC change. Specifically, in volcanic areas, the spatial variation of soil andic properties usually explains the spatial variation of topsoil SOC contents, but SOC data for deeper soil layers are needed. We measured the andic properties (e.g. pyrophosphate extractable aluminium and allophane contents) and SOC stocks down to 200-cm depth in a 1 km<sup>2</sup> micro-watershed covered by Arabica coffee agroforestry in Costa Rica. We used diffuse reflectance mid-infrared (MIR) spectroscopy to allow a large number of soil analysis. The objectives of our study were (i) to evaluate MIRS as a low-cost and rapid tool to measure andic properties and SOC in Andosols and (ii) to predict the level of SOC stocks down to 200-cm depth.</p>