Most of the sampled soils, independent of their parent material and
management, were strongly acidic (soils 1 to 14), with pH values ranging between 3.2 (P5 in Ah horizon) and 4.9 (P8 in BgBw horizon).
Only P15 and P16 were less acidic (pH N 5) which might have been
mainly due to the still operating H+ buffer system of the formerly
base-rich parent material (dolerite). The generally low pH in soils of
the study area can be attributed to the local climatic conditions which
are responsible for intensive chemical weathering of soil minerals and
leaching of base cations. Even soils under agricultural use (all soils
with Ap and MAp horizons) were acidic. This is because liming, which
would counteract soil acidification, up to now has not been very common
in Rwandan agriculture