Phosphorus accumulation in farm ponds and dams in southwestern Australia

Eutrophication of farm ponds and dams (earth tanks) due to elevated dissolv ed phosphorus concentrations causes death of fish, crustaceans, and animals . Phosphorus accumulation in water and sediment in 50 farm ponds and dams a nd 2 streams was investigated for a 4000-ha area near York, Western Austral ia. Water, sediment, and soil samples were analyzed for total, inorganic, a nd organic P. Sediments contained between 4 and 54% day. The major minerals in the clay fraction were quartz, kaolinite, and smectite with minor amoun ts of illite, felspars, calcite, and iron oxides. Sediments contained betwe en 0.4 and 5.9 g kg(-1) N, 6.0 and 14.3 g kg(-1) AI, 15.0 and 77.0 g kg(-1) Fe, and 3.0 and 80.0 g kg(-1) organic carbon. The dissolved P concentratio n in pond, dam, and stream water ranged from 0.001 to 4.15 mg L-1 and suspe nded particulate P (>0.22 mum) ranged from 0.016 to 2.78 mg L-1. Total P in sediments ranged from 29 to 1101 mg kg(-1) compared with 134 to 554 mg kg( -1) in soils. Inorganic P accounted for 57% of total P in sediments and 75% of total P in soils. Relationships between concentrations of total P, inor ganic P, and organic P in sediments and dissolved P in dam water were linea r, indicating a buffering action of the sediment constituents on dissolved P. There was a linear relationship between the concentrations of P in sedim ents and in soils of catchments.