Loss of Phosphorus by Runoff from Watersheds in West Virginia.

Nutrient in runoff from soils treated with heavy manure application is a major cause of poor surface water quality in the United State. Poultry production in Hardy County, WV has increased considerably since the early 1990s. The Lost River basin contains the highest density of poultry houses in the county. Most of the P-rich manure produced is land applied, and concerns over water quality are widespread. The objective of this study was to apply the NRCS technique on two watersheds (Cullers Run (CR) and Upper Cove Run (UCR)) in the Lost River basin to predict the loss of water and P from soils by runoff, and to estimate the impact on water quality. The predicted average runoff was 4,374 m3/ha/yr, and agreed with the observed average runoff of 4,267 m3/ha/yr. This gives an annual runoff of 74.6 million m3 for the two watersheds. The average P loss by runoff was 0.57, 1.98, and 5.51 kg/ha/yr from soils under forest, pasture, and crop, respectively. The high P loss by runoff was probably associated with application of P fertilizer or poultry manure to cropped soils. The total annual loss of P from soils by runoff was estimated at 16,435 kg. The predicted P concentration varied widely in runoff water generated from different soils and land covers. The average P concentration in runoff water was 133, 432, and 1,146 µg/L for forestland, pastureland, and cropland, respectively. The predicted average P concentration in runoff was 224 µg/L for the two watersheds. However, the observed P concentration was very low (1.3 to 13.3 µg/L) in the monthly water samples (Jan. to Dec., 2006) collected from the Lost River where the pH ranged between 7.6 and 8.4. The average pH in soils was 4.22, 5.42, and 6.15 for forestland, pastureland, and cropland, respectively. Changing the pH of runoff water from acidic (soils) to the alkaline range in the Lost River could precipitate calcium phosphates and decrease P concentration in water. The technique predicted P concentration in runoff at the edge of field. The increase in water pH as well as P removal by aquatic weeds and algae could be the cause of the low P concentration observed in the Lost River.