Impacts of Soil and Water Conservation Structures on Selected Soil Physicochemical Parameters in Wali Micro-Watershed Ambo District, Central Ethiopia.

Land degradation poses a significant environmental challenge, leading to reduced soil fertility, agricultural production, and overall land productivity. To combat this issue, the Ethiopian government has implemented various soil and water conservation (SWC) strategies in rural areas over the last few decades. This study assessed the impact of these SWC structures on selected soil physicochemical properties in Wali micro-watershed. A purposive sampling technique was used to select the study district and watershed, and a systematic randomized complete block design was used to collect soil samples. Samples were taken from both farmlands conserved with various SWC practices, like soil bund, stone bund, terraces, fanyajuu, and bench terrace, all from nonconserved lands along the lower, middle, slope classes using an "X" sampling design. Eighteen composite soil samples for all three slope classes were collected in triplicate from topsoil (0-30-cm depth) for analysis. These samples were processed and analyzed following standard laboratory procedures in the Ambo University Chemistry Department. The study assessed soil bulk density, moisture, pH, cation exchange capacity, electrical conductivity, organic matter, organic carbon, total nitrogen, available phosphorus, available potassium, and other basic cations (sodium, calcium, and magnesium). The results showed that conserved farmlands had mean values of 1.26 g/cm³ for bulk density, 6.72% for moisture, 6.29 for pH, 4.32% for organic matter, 2.24% for organic carbon, 0.30% for total nitrogen, 53.02 cmol/kg for CEC, 37.28 dS/cm for electrical conductivity, 25.80 mg/kg for available phosphorus, and 0.91 mg/kg for available potassium. In contrast, nonconserved farmlands exhibited 1.37 g/cm³ for bulk density, 6.07% for moisture, 5.86 for pH, 3.12% for organic matter, 1.84% for organic carbon, 0.21% for total nitrogen, 46.6 cmol/kg for CEC, 37.23 dS/cm for electrical conductivity, 21.06 mg/kg for available phosphorus, and 0.63 mg/kg for available potassium. The study concluded that SWC practices significantly improved soil bulk density, moisture content, pH, organic carbon, organic matter; cation exchange capacity, total nitrogen, sodium, available phosphorus, and potassium. However, electrical conductivity, calcium, and magnesium showed no significant improvement (p < 0.05). These findings highlight the positive effects of SWC structures on soil quality, underscoring the importance of maintaining these practices for sustainable land management and advocating for their expansion to other watersheds.