Effect of land use change and overgrazing on runoff, sediment and soil phosphorus losses in the Soolegan Watershed

The discharge of total suspended sediments (TSS) and dissolved nutrients from watersheds into receiving waters is a serious problem when natural vegetation is degraded by agriculture or overgrazing. This study was conducted in Soolegan Watershed to investigate land use change and overgrazing effects on phosphorus loss (dissolved & particulate), particle size associated loss of P and effect of time of rainfall on total dissolved P concentration in runoff. Much higher runoff, sediment and nutrient losses observed under cultivated land and HDP (high degraded pasture) than those under MDP (moderately degraded pasture). Contribution of particulate phosphorus exported from micro plot via surface runoff was increased by decreasing plant cover. Largest amount of dissolved phosphorus loss measured in HDP (16.4 mg/m2) and particulate P loss in cultivated land (301.3 mg/m2). Concentration of total dissolved phosphorus (TDP) in runoff was significantly (p