Residual Effects of Compost and Fertilizer Applications on Nutrients in Runoff

The application of compost or fertilizer at rates that exceed crop nutrient requirements can result in phosphorus(P) and nitrogen (N) accumulation in soil. This study was conducted to determine the influence of soil P and N contents onthe concentrations and total amounts of P and N transported in runoff. Composted beef cattle feedlot manure or inorganicfertilizer were added from 1992 to 1995 to a Sharpsburg silty clay loam soil at rates sufficient to meet P or N requirementsfor corn and incorporated following application. After four years of corn production following the last compost application,P concentration, EC, and pH of the surface soils on the Nbased compost treatments were significantly greater than the checkplots. Simulated rainfall was applied to the experimental site in 2000. Concentrations and total amounts of P and N in runoffwere similar on the compost and inorganic fertilizer plots. The application of corn residue at a rate of 6 Mg ha1 did notsignificantly affect the nutrient concentration of runoff or total nutrient transport when compared to a noresidue conditionfor a study site with a slope varying from 0.15% to 2.70%. On an adjoining field, compost or inorganic fertilizer were appliedat rates in excess of crop P and N requirements to increase soil test P levels. For Bray and Kurtz No. 1 soil test P levels rangingfrom 42 to 267 mg kg1 and watersoluble soil test P values varying from 5 to 61 mg kg1, the dissolved P (DP) concentrationof runoff did not correlate well with soil test P. Thus, factors other than soil test P appear to influence P loss in runoff forthe bare soil used in this investigation.