Erodibility and Gully Erosion in Relation to Soil Properties in Akwa Ibom State, South Eastern, Nigeria

This study was conducted to evaluate soil physical and chemical properties in relation to erodibility and gully erosion in Akwa Ibom State, South eastern Nigeria. The locations of study were three gully erosion sites/ types, namely, active and meta-stable (ms-1 and ms-2) gullies. Results of the study showed that coarse sand (CS) particles averaged 863, 710 and 800 gkg-1 in the active and ms-1 and ms-2 respectively, and were several orders of magnitude greater than the fine sand particle. The silt particle averaged 20, 94 and 41g kg-1 , while the clay fraction averaged 66,139 and 86 g kg -1 in the respective locations. Clay ratio (CR) averaged 12.14, 3.59 and 9.18, while silt/clay ratio averaged 0.32, 0.76 and 0.46, in the respective sites. Soil texture was either sandy loam (sl) or loamy sand (ls) generally. Wet aggregate stability (WAS) >2-mm averaged 15.8, 19.8 and 21.6%, while >0.5–mm averaged 34.2, 26.8 and 27.1% in the respective locations. Values of erodibility (K) were generally low, averaging 0.045, 0.065, and 0.053 ha-1 MJ-1mm-1 respectively. Soil organic C (org C) averaged 0.87, 1.22 and 1.72 gk g-1 , respectively. Sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) respectively averaged 0.04, 0.04 and 0.04, and 1.20, 1.79 and 1.56% in the active and ms-1 and ms-2. Oxides of iron averaged 2181.9, 1851.0 and 2891.4 mg kg -1 (crystalline) and 1047.7, 1923.4 and 1978.2 mg kg-1 (amorphous), respectively. The index of susceptibility, K, correlated positively with silt (si) (r=0.877**) and clay (cl) (r=0.795**), and negatively with CS (r=-0.902**) and CR (r=-0.694* ). The values of the silt and clay fractions indicate low content of inorganic colloids, while the CR indicates high soil dispersion potential irrespective of the moderately high values of soil organic C or organic matter and macro-aggregation. Consequently, the soils could be easily eroded, the low values of K notwithstanding.