Preferential transport of phosphorus from surface-applied poultry litter in soils from karst and non-karst landscapes

Authors: KATUWAL, SHEELA - University Of Arkansas; Ashworth, Amanda; Moore, Philip; BRYE, KRIS - University Of Arkansas; Schmidt, Michael; Vanotti, Matias; Owens, Phillip

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2022
Publication Date: 4/26/2022
Citation: Katuwal, S., Ashworth, A.J., Moore Jr, P.A., Brye, K., Schmidt, M.D., Vanotti, M.B., Owens, P.R. 2022. Preferential transport of phosphorus from surface-applied poultry litter in soils from karst and non-karst landscapes. Soil Science Society of America Journal. 86:1002-1014. https://doi.org/10.1002/saj2.20424.
DOI: https://doi.org/10.1002/saj2.20424

Interpretive Summary: Karst landscapes are formed by natural dissolution of soluble rocks and cover approximately 25% of the continental U.S. landmass. Current nutrient management plans do not consider leaching losses in karst landscapes. However, these geologic landscapes can transport contaminants and nutrients rapidly through soils to drainages systems. This information is particularly needed in sensitive areas with highly permeable bedrock, such as in karst topographies. These areas likely have direct soil surface to groundwater drainage although the extent of this is unknown. A team of ARS scientists extracted large (0.5 x 1.5 m), intact natural soil ‘columns’, which are among the largest to-date for determining actual leaching in soil profiles of karst and non-karst landscapes. In this study, researchers applied phosphorus-rich poultry litter in a rainfall simulation experiment and measured nutrients in the leachate. This study found that soils from karst landscapes had 8 times greater nutrients in leachate, particularly phosphorus, which causes algal blooms and water quality concerns. Results indicate that karst landscapes are very vulnerable to phosphorus transport into deeper soil layers; therefore, soils overlying karst systems have the potential to pose a threat to surface and groundwater quality over time.

Technical Abstract: Preferential transport of phosphorus (P) in manure-amended soils through soil macropores can be a significant source of diffuse-P pollution, although studies quantifying P losses are lacking. Intact soil columns (40 diameter × 100 cm tall) collected from a karst and non-karst landscape (three replicates per soil landscape) were used to evaluate the role of preferential flow on P transport from surface-applied poultry litter. Losses of P in leachate in dissolved (DP) and particulate (PP) forms, as well as total P (TP), were quantified after poultry litter application (5.6 Mg ha-1) following three successive irrigation events (3.9 cm h-1 for 2 h). Dissolved P constituted the major fraction of leachate-P loss as more than 80% of the total P, which peaked (5.61 mg L-1) following the first irrigation event after litter application and decreased to about half (2.88 mg L-1) by the third irrigation event. Soils from karst landscapes had greater (P < 0.05) leachate volume and total P, with approximately eight times greater losses than from non-karst soils. Results indicate that the top 1 m of soil in a karst landscape is vulnerable to vertical P transport into deeper soil layers; therefore, soils overlying karst systems have the potential to increase legacy P and pose a threat to surface and groundwater over time.