Influence of Parent Material and Topography on some Soil Properties in Southwestern Nigeria
Selected physical and chemical properties and nutrient ratios on three landscape positions (interfluve crest, middle slope and foot slope) were examined on soils formed on banded gneiss and quartzite schist parent materials. Parent material significantly (p<0.05) influenced gravel, coarse sand and copper contents in the soils examined. Gravel, coarse sand and copper contents were significantly (p<0.05) higher in soils formed on quartzite schist parent material than on banded gneiss. Out of 25 soil parameters considered in this study, parent material influence was limited to 3 properties, representing 12% influence. Topography significantly influenced 7 properties (gravel, coarse sand, clay, pH in water available P, exchange acidity, and Cu) of the 25 examined representing 28 influence, which is 2 times that of parent material. Differences among topographic positions reflected soil properties that are typically associated with bio and geochemical processes (weathering and leaching). Parent material × topography interaction was significant (p<0.05) for Fe. With respect to chemical soil fertility, soils developed on banded gneiss and quartzite schist parent materials in southwestern Nigeria should be put to the same management. Possible limitations of root impedance and reduced moisture retention imposed by high gravel and coarse sand contents on soils developed on quartzite schist should also be taken into consideration. Delineations of land management units with respect to topographic position (facets) rather than with parent material is justified since a strong association exists between topography and soils.
Keywords: Parent material, topographic gradients, soil variability, tropical soils, Nigeria.
Nigerian Journal of Soil and Environmental Research Vol. 7 2007: pp. 1-6