Dissolved Nutrient Losses in Storm Runoff from Five Southern Pine Watersheds

Abstract

AbstractStorm runoff from five reforested eroded watersheds in northern Mississippi (1.5 to 2.8 ha) was analyzed during the 1973 water year to determine the concentrations of soluble NO3‐N, NH4‐N, PO4‐P, Ca, Mg, and K. Storm runoff was measured with 0.91‐m H‐flumes and samples collected with a Coshocton wheel sampler. Analysis of precipitation which totaled 189 cm for the year, 40% above average, revealed that inputs of NO3‐N, NH4‐N, PO4‐P, Ca, Mg, and K for the year were 3.12, 5.73, 0.07, 7.72, 3.03, and 4.98 kg/ha, respectively. Soluble nutrient losses in the storm runoff on a unit area basis were similar for the five watersheds. Average losses in storm runoff of soluble NO3‐N, NH4‐N, PO4‐P, Ca, Mg, and K for the year were 0.32, 3.35, 0.04, 6.21, 3.05, and 3.31 kg/ha, respectively. As the annual storm runoff among the watersheds increased, the NO3‐N losses also increased linearly. Data for individual storms indicated that a critical storm runoff value must be exceeded before the watersheds would exhibit a net loss of each nutrient.