Plant Nutrient Losses from Tile‐Outlet Terraces

Abstract

AbstractPlant nutrient losses in runoff water from four tile‐outlet terrace systems in Iowa and in tile drainage from two of the systems were measured annually from April to November over a 3‐year period. Total P losses in surface runoff varied from 0.44 to 1.06 kg/ha and, at any one location, were highly correlated with sediment losses. Average annual concentrations of total P in surface runoff ranged from 1.01 to 3.60 ppm and in tile drainage from two sites were 0.028 and 0.061 ppm. Soluble P concentrations in surface runoff were related to available P in the surface soils, and concentrations in tile drainage were related to available P in the subsoils. Annual average inorganic P concentrations in surface runoff varied from 0.013 to 0.204 ppm and in tile drainage were 0.004 and 0.018 ppm. Concentrations of inorganic N varied widely among locations, but were relatively constant at a location. Average annual inorganic N concentrations in surface runoff were 4 ppm or less at three of the four sites and 11 ppm at one site. Concentrations of inorganic N and sulfate S were similar and were lower in surface runoff than in tile drainage. There was no relation between the amounts of fertilizer applied and plant nutrient losses or concentrations in runoff or drainage water.