Classification and fertility status of soils on slopes of varying orientations in Umuahia area of Abia State, Nigeria

Abstract

The slope orientation and position of toposequence influence soil properties along the landscape. The study classified and evaluated the fertility status of soils on slopes of varying orientations in Umudike (East-lying Toposequence) and Itu (West-lying Toposequence) located in Olokoro Umuahia, Abia State southeastern Nigeria. Transect soil sampling technique was employed in locating 3 distinct top units (Summit, Midslope and Footslope) along each of the toposequence. Soil profile pit was dug at each top unit, described using FAO guidelines and sampled according to genetic horizons. Soil samples collected were subjected to routine laboratory analyses. Pedons were classified using the USDA Soil Taxonomy System and correlated with World Reference Base while the fertility status was evaluated using elemental ratios. The results indicated that soils of the two toposequence were dominated by sandy clay loam texture. Consistency of the pedons generally varied from very friable (Vfr) to very firm (Vfi) in the two toposequence. Soil pH was very strongly acidic (4.58-4.78) in the east lying toposequence but varied from very strongly acidic to strongly acidic (4.52-5.30) in the west lying toposequence. Organic matter concentration was higher at the epipedons and ranged from 26.44 to 23.36 g kg -1 and 18.9 to 30.64 g kg -1 in soils of east-lying and west-lying slopes, respectively. K: Mg ratio varied from 0.01- 0.12 and 0.01-0.08 at the east and west lying slopes, respectively. The pedons of the summit, midslope and footslope were as classified Grossarenic Paleudalfs, Typic Paleudalfs and Arenic Hapludalfs for respectively for the east-lying slope and Arenic Glossudalfs, Typic Paleudalfs and Typic Ferrudalfs, respectively for the west-lying slope. Generally, the two toposequences were of poor fertility status.