Abstract

Raphael Pinheiro Machado Rehm and Sven Grashey-Jansen

 During a two month fieldwork, soil profiles were dug along one of the numerous hill slopes of the Ugandan rolling hills in the Masaka District. The topsoil of each profile was sampled and analyzed on grain size distribution and pH-value, to get information about soil development caused by erosion processes and lateral water movement. The soil survey confirmed a catenary sequence in the studied area. Loamy soil had a massive thickness at the upper slope but showed a surprisingly stable formation at the steep shoulder position. Small clay particles that concreted as pseudosand were able to stand erosion while the waterlogged soils on flat spots got suspended. A translocation of unfixed and loose soil particles was caused by a highly developed lateral water movement. Soils on the foot slope showed hydromorphic features and accumulation of fine particles from the upslope at the bottom of the valley. Furthermore, seasonal variations of the ground water level led to an irreversible concretion at the foot slopes, called petroplinthit. It was remarkable that all soil layers were significantly enriched by quartz grains.The traditional catenary conception was used to derive the spatial distribution of soils from geomorphological field parameters.