Preferential transport of phosphorus from surface‐applied poultry litter in soils from karst and nonkarst landscapes

Abstract

Preferential transport of P in manure-amended soils through soil macropores can be a substantial source of nonpoint P pollution, although studies quantifying P losses from intact soil columns are lacking. Large, intact soil columns (45 cm diam. by 100-cm height) collected from karst and nonkarst landscapes (three replicates per soil) were used to evaluate the role of preferential flow in P leaching from surfaceapplied poultry litter. Losses of P in leachate, dissolved P, and total P were quantified following poultry litter application (5.6 Mg ha -1 ) and three successive simulated rain events (3.9 cm h -1 for 2 h). Dissolved P constituted the major fraction of leachate-P loss as more than 80% of TP, which peaked (5.61 mg L -1 ) following the first irrigation event after poultry litter application and decreased to about half (2.88 mg L -1 ) by the third irrigation event. Soils from the karst landscape had greater (p < .05) leachate volume and total leached P, with approximately six times greater losses occurring than nonkarst soils. Results indicate that the top 1 m of soil obtained from karst landscapes is vulnerable to vertical P transport into deeper soil layers. Therefore, soils with substantial preferential flow pathways may increase legacy P in subsurface soil and pose a threat to surface and groundwater over time.