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

Abstract

AbstractPreferential 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 surface‐applied 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.