Aqueous‐ and Sediment‐phase Phosphorus Yields from Five Southern Pine Watersheds

Stormflow from five reforested watersheds (1.5 to 2.8 ha) in northern Mississippi was analyzed during the 1974 water year (Oct. 1973 to Sept. 1974) for phosphorus (P) in solution and in association with suspended sediments. Samples were collected for each storm with Coshocton wheel samplers set below 0.91‐m H‐flumes. For the year, mean concentration of total P in solution was 0.027 mg/liter for the five watersheds. Of this, 45% was hydrolyzable P, 33% ortho‐P, and 22% organic P. Sediment total P concentrations ranged from 274 to 1,067 µg/g and were 2.0 to 8.9 times that in the watershed soils. Increased concentration of P in suspended sediment relative to soil is attributed to selective erosion of fine sediments and/or deposition of coarse sediments in transport. For the five watersheds, solution total P yield during the water year averaged 88 g/ha; whereas sediment total P yield averaged 210 g/ha and accounted for 64 to 76% of the sediment plus solution P yield.