A three-dimensional perspective of phosphorus retention across a field-buffer strip transition

• Published in: Environmental research Vol. 233; p. 116434
• Main Authors: Ramler, David, Inselsbacher, Erich, Strauss, Peter
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 15.09.2023
• Subjects: Degree of phosphorus saturation (DPS); Phosphorus sorption index (PSI); Riparian buffer strip; Soil core sampling; Surface water protection; Vegetated filter strip; Riparian buffer strip; Vegetated filter strip; Phosphorus sorption index (PSI); Soil core sampling; Surface water protection; Degree of phosphorus saturation (DPS)
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.116434

Vegetated filter strips (VFS) act as buffer zones between fields and water bodies that are supposed to retain incoming runoff, sediment, and nutrients. The factors that govern nutrient retention and cycling in VFS are complex and act in all three dimensions. A key element that determines VFS effectivity is flow type, e.g., sheet vs. concentrated flow. These aspects are, however, often insufficiently accounted for in VFS research and design recommendations. In this study, we attempt to tackle these shortcomings by examining the nutrient distribution in detail at two field-VFS transitions, applying a three-dimensional sampling array together with extensive laboratory analyses. Concentrated runoff was the dominant type we found and we argue that flow convergence is the norm rather than the exception. Further complicating this issue is that entry locations of runoff may vary, calling for more sophisticated sampling designs. Overall trends were similar across the analyzed nutrient fractions (different K- and P-pools) and there were distinct trends of decreasing nutrients along the longitudinal (from the field to the VFS) and vertical planes. The horizontal plane (from outside to inside the area of concentrated flow) showed mostly inconclusive or U-shaped gradients. Both sites were similar and close to each other, nevertheless, there were significant differences that affected nutrient retention in the VFS which were linked to site-specific factors. The spatial extent (i.e., width) is often considered the main variable in VFS designs. However, other VFS traits such as vegetation type and structure, as well as external factors such as field topography and the severity of erosive events are equally important and should be attributed more significance. •Vegetated filter strips (VFS) protect surface waters from sediment and nutrient input.•VFS design and research is often oversimplified, e.g., not viewed in 3D.•Nutrient distribution in the soil shows distinct gradients along all spatial planes.•Differences in nutrient retention are caused by site-specific factors.•An elaborate 3D approach is indispensable for a holistic VFS assessment.