Preferential flow under high-intensity short-duration irrigation events in soil columns from a karst and nonkarst landscape

Authors: KATUWAL, SHEELA - University Of Arkansas; Ashworth, Amanda; Owens, Phillip

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2021
Publication Date: 9/22/2021
Citation: Katuwal, S., Ashworth, A.J., Owens, P.R. 2021. Preferential flow under high-intensity short-duration irrigation events in soil columns from a karst and nonkarst landscape. Vadose Zone Journal. 20(6). Article e20160. https://doi.org/10.1002/vzj2.20160.
DOI: https://doi.org/10.1002/vzj2.20160

Interpretive Summary: Preferential flow of water through soil macropores, also known as macropore flow, can transport contaminants rapidly through soils to drainages systems. Karst landscapes are formed by natural dissolution of soluble rocks and cover approximately 25% of the continental U.S. landmass and are characterized by high levels of macropore flow. Knowledge of the extent of macropore flow in different topographies is crucial for the effective implementation of nutrient management plans. Researchers investigated the prevalence of macropore flow in soil columns obtained from karst and non-karst soils using a Bromide (Br¯) tracer. A tracer solution was applied on the soil surface and then the soil columns irrigated. Effluent drained from the soil column was measured for water and Br¯ losses. Soil from the karst landscape drained five times greater volume of water and Br¯ tracer compared to soil from non-karst landscape. Thus, it is suggested that management plans for nutrient loss reduction in karst landscapes should also consider reducing nutrient leaching losses in macropore flow.

Technical Abstract: Preferential flow through soil macropores is a major cause of rapid transport of contaminants through soils to drainages systems. Knowledge of the extent of macropore flow in different topographies is crucial for the effective implementation of nutrient management plans. The objective of this study was to determine the extent of preferential flow in karst and non-karst soils using a Bromide (Br¯) tracer. Intact soil columns (40 × 100 cm) collected from karst and non-karst systems (two replicates per treatment) were subjected to two rainfall simulation events which included application of Br¯ tracer solution at concentrations of 3.02 and 1.15 g L-1 during simulation 1 and 2, respectively, each followed by irrigation events repeated five successive times (5.67 mm min-1 for 2 min in 30 min intervals). Soil columns rested on a stainless-steel grid (consisting of 100 cells, each measuring 3.81 × 3.81 cm) which facilitated column partitioning and drainage collection from each grid. Results indicate soil treatment (kart and non-karst) largely drives drainage losses (water and Br¯) through 1 m deep soil profiles, with soils from karst landscapes draining approximately five times greater than soils from non-karst landscapes. Consequently, soils from karst landscapes are more susceptible to leaching losses compared to soils from non-karst landscapes. Further studies under different flow regimes and encompassing different soil units may be beneficial in understanding the potential leaching risk in these areas and for implementing best management practices for landscape-based nutrient management.