Digital Soil Mapping of Soil Organic Carbon in Namibia Using Google Earth Engine

The Namibian Soil Profile Database contains 4960 entries, all samples with geographic coordinates. Each soil property presents a different number of observations, which decreases with depth. To perform the Digital Soil Map of Soil Organic Carbon (SOC) up to 30 cm, 1298 sample points were used. The covariates used in the model were composed from land cover, geology, terrain characteristics extracted from the digital elevation model and remote sensing data. Most of the covariates carry 30 m of spatial resolution. The Random Forest model implemented in Google Earth Engine (GEE) was applied with an external validation split of 80/20 %. As the second validation layer, samples from the Namibian tier of the Soils4Africa project were applied. The use of GEE facilitated the generation of a SOC distribution map for Namibia at a spatial resolution of 30 × 30 m. The highest amounts of SOC are stored in the central region of Namibia, with SOC values ranging from 0.1 to 1.9 %. The map is suitable for national and regional decision-making, offering a baseline for determining SOC stocks, monitoring changes in SOC, assessing the effects of bush encroachment/thickening and bush control, and for agriculture implications. Mapping of soil properties in other depths are scheduled for the near future.