Effect of Slope Aspect and Land Use Types on Selected Soil Physicochemical Properties in North Western Ethiopian Highlands

Abstract

Recent research findings imply that the slope aspect has a great impact on soil genesis and soil microclimate. The microclimate has a significant effect on the soil geobiochemical processes taking place in the soil. However, the slope aspect impact on soil properties has not been yet studied well in Ethiopia, particularly in the northern highlands. This research was initiated to link selected soil physicochemical properties with slope aspects under different land use practices. The research was conducted in Gumara-Maksegnit watershed located at the upper Lake Tana basin, Ethiopia. Four slope aspects, eastward (Ew), northward (Nw), southward (Sw), and westward (Ww), and three land use types at each slope aspect, cropland (Cl), forest land (Fl), and grazing land (Gl), were considered. In total, 36 undisturbed soil samples for bulk density and 36 disturbed soil samples for selected soil properties were collected. Soil particle size (texture), bulk density, electrical conductivity (EC), soil pH, available phosphorus (av. P), available potassium (av. K), total nitrogen (TN), and soil organic carbon (SOC) were analyzed. The resulting analyses showed no significant variation (p<0.05) across both slope aspects and/or land use types for soil pH and EC, whereas the slope aspect showed a significant effect (p<0.05) on SOC, TN, av. K, and av. P. The highest significant (p<0.05) mean value of SOC was observed in the Ww (3.04%) followed by Nw (2.52%) but SOC was not significant (p<0.05) between Sw and Ew. While the highest av. K (1233.2 centimole/kilogram) and av. phosphorus (35.76 ppm) were observed in Nw slope aspect, the highest TN was in the Ww slope aspect (0.24%). The significant effect (p<0.05) of land uses can be summarized as Fl > Gl > Cl for SOC and TN. A strong positive correlation was observed between SOC and TN (R2 = 0.997) and av. K and av. P (R2 = 0.58) at p<0.05. Generally, the slope aspect, land use types, and their interaction had a significant effect on soil physicochemical properties.