Effect of Tillage and Nutrient Source On Runoff and Leaching Losses of Phosphorus.

Phosphorus is essential for the growth of plants and is commonly a limiting nutrient in aquatic ecosystems.  Excess phosphorus losses from agricultural systems have been linked to eutrophication and water quality degradation.  Although phosphorus is relatively immobile in soil, phosphorus leaching has been documented where phosphorus loading has exceeded adsorption capacity of the soil, sandy soils, soils with high organic matter contents, and soils with macropores and preferential flow pathways.  The objective of this field study was to quantify the effects of tillage and nutrient source on both runoff and leaching losses of total and dissolved phosphorus. The study site was located at the University of Wisconsin Agricultural Research Station near Lancaster, WI.  Tillage plots at the site included chisel plow and no-tillage. These tillage treatments have been in operation since 1993 and the study was conducted from 2003 to 2007.  The nutrient sources were two types of manure (hog and beef manure) and urea fertilizer (control treatment- no phosphorus addition).  Leahate samples were collected from a series of pan and wick lysimeters located at 0.6 and 1.2 m below the soil surface, while surface runoff from each plot was collected by isolating plots with galvanized sheet metal and collecting water in 1.7 m wide runoff collectors. In this presentation, we summarize total and dissolved phosphorus concentrations and loads over the study period.