Effect of slope aspect and position on soil infiltrability in an ultisol in Akwa Ibom State, southern Nigeria

Soil infiltrability is an important hydrological process that enhances soil water storage and the minimization of runoff. A study was conducted to evaluate the effect of slope aspect (north, NfS and south, SfS) and positions [(crest (CR), upper (US), middle (MS) and lower (LS)] on soil infiltrability,  that is, initial infiltration rate (io), steady-state infiltration rate (ic) and cumulative infiltration (I), and sorptivity (S) and transmissivity (A) on the University of Uyo Teaching and Research Farm (T&SF) located on an Ultisol in Akwa Ibom State, southern Nigeria. Results show that the initial  infiltration rate (io) was 43.20 cm h−1 on SfS and significantly (p < 0.05) higher than 36.60 cm h−1 on NfS. The final infiltration rate (ic) was not significantly different between NfS (9.60 cm h−1) and SfS (7.20 cm h−1). The Cumulative depth of water (I) infiltrated was similar between NfS (28.18 cm) and SfS (21.46 cm). Soil water sorptivity (S) was moderately high on the two slopes but significantly (p < 0.05) lower in NfS (0.49 cm min−1/2)  than in SfS (0.70 cm min−1/2) soil. Soil water transmissivity (A) was similar in NfS (0.19 cm h−1) and SfS (0.16 cm h−1) soil. The results indicate that the aspects were similar in io, ic, I, S and A. However, since soil texture is similar among the aspects, similar soil management practices, example tillage  and mulching, could be adopted to enhance water infiltration to improve ic for increases in soil water conservation and crop production on the  T&SF. Key words: slope aspect and position, soil infiltrability, sorptivity and transmissivity, soil water management