Gully Category, Slope Position and Soil Depth Studies of ‘Acid Sand’: Their Effects Upon Soil Physical Properties in Akwa Ibom State, Southeastern Nigeria

Abstract

The menace of gully erosion is quite alarming on soils of coastal plain sands of southeastern Nigeria. Consequent upon this, a study was conducted to determine effect of Gully Categories, gully slope position and soil depth affect soil properties on coastal plain sand, Akwa Ibom State, Southeastern Nigeria. The study was conducted in nine (9) gully erosion sites. The gullies were grouped into three broad categories based on their dynamics namely, Active gullies, Meta stable gullies and Stabilized/old gullies at three Gully slope positions of upper slope, middle slope and Lower Slope with a control site. Samples were collected with a spade at 0-20cm and 20-50cm depths. Data generated were fitted into a 3 x 3 x 2 factorial designed and were assessed with the used of analysis of variance. The result revealed that under gully category, there was no significant effect of gully category on content of Fs, Cs, Ts, Silt and Clay, but sand fraction dominated other soil particle fractions also, SOG > MsG >AcG soil in saturated hydraulic conductivity, and was affected by gully category. Result of bulk density affected by gully slope position obtained shows the lowest bulk density in CT soil (1.38 mgm-3), followed by LS soil (1.39 Mgm-3) and US (1.44 Mgm -3) soils, which were statistically equal. Effect of depth shows that 0.20cm depth, Fs, Cs, Ts, silt and clay had mean values of 256, 525, 780, 50 and 169 gkg-1, respectively, while 20-50cm depth, Fs Cs, Ts, Silt and Clay recorded mean values of 262, 523, 784, 52 and 164 gkg-1, respectively. Permanent wilting point was also significantly affected by the interaction of Gully Category, Gully Slope position and soil depth. The combination of SOG and subsoil showed high PWP at the CT, US and Ms, when compared to other combinations (ACG and MSG) with exceptions in ACG x US x Subsoil and MSG x US x Topsoil and MSG x US x topsoil and Subsoil, which were at the same level with the earlier mentioned combinations involving SOG.