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.
The effect of clearcutting loblolly pine (Pinus taeda L.) on concentrations of sediment and nutrients in stormflows was studied on small catchments near Lexington, TN. The plantations were established on eroded and abandoned agricultural lands with fragile soils. Soil series on the catchments include Lexington silt loam (fine‐silty, mixed, thermic Typic Paleudalfs), Providence sill loam (fine‐silty, mixed, thermic Typic Fragiudalfs) and Ruston sandy loam (fine‐loamy, silicious, thermic Typic Paleudults). Eight catchments (0.17–0.56 ha) were instrumented with flumes equipped with water stage recorders to measure stormflow and Coshocton wheel samplers to obtain integrated samples of the flow. Plantations on four catchments were clearcut; the other four were left as uncut controls. Stormflow samples were analyzed for sediment‐phase total Kjeldahl nitrogen (TKN) and total phosphorus (TP) and solution‐phase TKN, TP, and potassium (K). Results indicated that a third or more of the TKN and two‐thirds of the TP exported in stormflow from the catchments was via sediment. Solution‐phase TKN and TP concentrations in stormflow were similar on clearcut and control catchments. Solution K concentrations were consistently higher from clearcut catchments. Rainfall inputs of TKN, TP, and K exceeded stormflow losses. The study demonstrated that pine plantations established on fragile soils can be clearcut without significant impact on water quality if recommended practices are used.
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