EFFECT OF PHYSICAL SOIL AND WATER CONSERVATION MEASURES ON SELECTED SOIL PHYSICOCHEMICAL PROPERTIES IN UBALE MICRO WATERSHED, ARBA MINCH ZURIA WOREDA, SOUTHERN ETHIOPIA

Abstract

Following erosion-induced soil degradation tremendous efforts have been made in implementing different soil and water conservation measures (SWC) in Arba Minch Zuria Wereda. Apart from monitoring and evaluation reports no substantive studies were made and documented on the performances of SWC measures in soil properties so far. The aim of the study is examine the effects of different SWC measures on the selected physicochemical properties of soil among physical SWC measures and position of terrace and, its improvement on soil infiltration rate. Reconnaissance survey was carried out and convenient sampling method was used to select the sampling plot. In cultivated fields treated by level stone bund and level soil bund each with 5 years old age from 15-25% slope category were compared with control. 9 experimental plots were selected. A total of 21 composite soil samples, 18 from treated and 3 from control were collected from the top 15 cm soil depth using “W” sampling design method and analyzed for soil texture, pH [H2O], electrical conductivity (EC), organic carbon (OC), organic matter (OM), total nitrogen (TN), available phosphorous (AP), zinc (Zn), exchangeable potassium (K+ ), exchangeable calcium (Ca2+) and exchangeable magnesium (Mg2+ ) using standard laboratory procedures. 21 undisturbed core samples, 18 from treated and 3 from control plots were collected and analyzed for bulk density (BD), total porosity (TP) and moisture content (MC). Infiltration rate of the soil was measured using a double ring infiltrometer. Results of the experimental study showed that soil MC (%), EC (ds/m), SOC (%), SOM (%), TN (%) and Ca2+ (cmol (+)/kg) were significantly different between SWC measures and the three different position within terrace. % clay were significantly different between SWC measures and interaction effect. Except pH all soil properties were significantly different between SWC measures. Equilibrium infiltration rate was reached on each treatment after (120mins), the LSTB had the highest basic soil infiltration rate, while the control and the LSB received medium and lowest infiltration rate respectively. SOC, SOM and TN were better on the level stone bund and soil bund than the control plot, while the control plots was received the highest pH, EC, Zn, Ca2+ and silt fractions compared with treated plot. The middle position within terraces recorded the higher OC, OM and TN than upper and lower position. Interaction effect of soil and water conservation measures by positions, the level stone bund in the lower position was recorded the higher OC and TN followed by level soil bund on the middle position. The cumulative values of physical SWC measures without proper attention for technical characteristics of the bunds and the maintenance systems improved were decreasing the marginal status of soil nutrients. Biological measures could be integrated for better effect soil fertility. Thus, further research need to be conducted on the effectiveness of bunds in relation to functions relevant for biomass and environmental quality