Nitrate, Phosphate, and Potassium Movement into Drainage Lines Under Three Soil Management Systems

Abstract

AbstractNitrate, orthophosphate, and potassium concentrations in drainage water were determined from subsurface drains installed in shallow‐tilled (ST), (15 cm); deep‐tilled (DT), (107 cm); and deep‐tilled and limed (DTL) Florida Oldsmar sand planted to citrus (Citrus sp.). The drainage water samples were collected during the period May 1971 through July 1972. Total discharge of NO3‐N was significantly greater from ST plots than either DT or DTL plots. The NO3‐N in the drainage water from all treatments ranged from < 1 – 8 mg/liter during the period of study. Concentrations <1 mg PO4‐P/liter were common in the drainage water from all plots during this period while K concentrations varied between 1 and 12 mg/liter. Peak concentrations and discharge of fertilizer nutrients were shown to be a function of rainfall, irrigation, and timing of fertilizations. Deeply incorporated limestone applications into the subsoil tended to increase the NO3‐N and decrease PO4‐P discharged over that from deep tillage alone.