Phosphorus Accumulation in Farm Ponds and Dams in Southwestern Australia

Eutrophication of farm ponds and dams (earth tanks) due to elevated dissolved phosphorus concentrations causes death of fish, crustaceans, and animals. Phosphorus accumulation in water and sediment in 50 farm ponds and dams and 2 streams was investigated for a 4000-ha area near York, Western Australia. Water, sediment, and soil samples were analyzed for total, inorganic, and organic P. Sediments contained between 4 and 54% day. The major minerals in the clay fraction were quartz, kaolinite, and smectite with minor amounts of illite, felspars, calcite, and iron oxides. Sediments contained between 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 concentration in pond, dam, and stream water ranged from 0.001 to 4.15 mg L-1 and suspended 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, inorganic P, and organic P in sediments and dissolved P in dam water were linear, indicating a buffering action of the sediment constituents on dissolved P. There was a linear relationship between the concentrations of P in sediments and in soils of catchments.