A study was carried out on soils developed from volcanic parent materials of Northern
Province of Rwanda to expose the current soil conditions, aiming largely on pedological
characterization but to a certain extent on assessment of potentials and limitations of soils
for production of major crops in the area. Three representative pedons namely KNG-P1,
KNG-P2and GHNG-P1were identified and described. Sixteen soil samples were collected
from different pedogenic horizons and analysed in the laboratory for physico-chemical
properties. Pedons were classified using USDA Soil Taxonomy and FAO-WRB for Soil
Resources. Results showed that soils were shallow to very deep and well drained. Topsoils
were very dark coloured with colour values of ≤ 2 in all pedons. Texture was generally
loamy with bulk densities of < 1.35 g/cm3
. Studied topsoils were medium acid (pH 5.57)
to mildly alkaline (pH 7.41), with high to very high organic carbon ranging from 3.97 to
13.03%. pHNaF was > 9.5 in Pedons KNG-P1 and KNG-P2, reflecting exchange complex
dominated by amorphous materials and/or humus complexes. Pedons KNG-P1 and KNGP2
met the “andic properties” requirement of phosphorus retention capacity≥ 85%.
Melanic index values indicated that these two pedons were characterised more by fulvic
than humic acids. Nutrient imbalance was observed in studied soils, implying suboptimal
nutrient uptake and toxicity. Degree of weathering of studied soils was low as indicated by
weathering indices. Pedons KNG-P1 and KNG-P2 were classified as Andisols/Andosols
and GHNG-P1 as Mollisols/Phaeozems. Land units represented by Pedons KNG-P1 and
KNG-P2 were rated as marginally suitable while land unit represented by Pedon GHNGP1
was rated as moderately suitable for the major crops of the area. Application of P
fertilizers coupled with efficient placement and soil conservation should be undertaken in
the study area