Savanna land use and its effect on soil characteristics in southern Ethiopia

We tested soil characteristics and nutrient availability linked to settlement age, grazing pressure and fire regime in southern Ethiopia. Settlement categories included: “non-settlement” (no evidence of settlement), “recent” (<15 years) and “old” (>40 years). Grazing pressure was represented by “enclosures” vs. “grazed areas”, while fire regime denoted by “burned” vs. “unburned” sites. Soil properties and vegetation characteristics were analyzed for different treatments. Our results showed that higher sand content could reduce soil pH values with increased leaching. Low soil pH could also occur due to the high rate of organic matter decomposition and uptake of cations by plants. We recorded higher nitrogen (N) and phosphorus (P) contents with N = 0.16 ± 0.01% and P = 21.10 ± 1.28 mg kg −1 in recent compared to old settlement. Electrical conductance (EC) was positively influenced by soil pH. We observed significantly higher EC under increased grazing. Higher soil pH, N, organic carbon (OC) and cation exchange capacity (CEC) were recorded in recent compared to non-settlement. Fire greatly improved soil condition, while heavy grazing reduced grass biomass. We suggest the need for appropriate land management and soil conservation by minimizing impacts of cultivation on soil characteristics. We also propose the reintroduction of fire to restore rangeland biodiversity. ► We examine soil nutrient dynamics linked to land use types. ► Increased leaching will reduce soil pH if sand content of a soil is higher. ► Uptake of cations by plants may induce low soil pH. ► Increasing grazing pressure will increase Electrical Conductance in the soil. ► Using fire as a tool for rangeland management will improve soil condition.