Site matters: site-specific factors control phosphorus retention in buffer strip soils under concentrated field runoff

Soil erosion from agricultural fields is a persistent ecological problem, potentially leading to eutrophication of aquatic habitats in the catchment area. Often used and recommended mitigation measures are vegetated filter strips (VFS) as buffer zones between arable land and water bodies. However, if they are designed and managed poorly, nutrients — especially phosphorus (P) — may accumulate in the soil. Ultimately, VFS can switch from being a nutrient sink to a source. This problem is further aggravated if the field runoff does not occur as uniform sheet flow, but rather in concentrated form, as is usually the case. To assess the impact of concentrated flow on VFS performance, we have taken soil core samples from field-VFS transition zones at six sites in Lower Austria. We determined a multitude of physical and chemical soil parameters, focusing on P fractions and indices. Our results revealed that concentrated flow can lead to an accumulation of P in the VFS. P levels in the VFS inside the area of concentrated runoff can be equal to or higher than in the field, even though they receive no direct fertilization. However, the concentration and distribution of nutrients in the fields and VFSs were also site-specific and affected by local factors such as the age of the VFS, cropping, and fertilization. Accordingly, there is a need for more sophisticated, bespoke VFS designs that can cope with site-specific runoff volumes and movements of nutrients that occur. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-024-34383-7.


Fig. A1
Fig. A1 Site SB. [A] Situation after a heavy rainfall event (July 2021).[B] Orthophoto of the VFS and the contributing agricultural area (2020).Green dots indicate the sampling poi nts; red dots the actual field/VFS border.[C+D] Detailed view of deposited sediment in the VFS and at the field/VFS transistion (July 2021).[E] overview of site SB (June 2020).
Fig. A2 Site AM. [A] Situation after a heavy rainfall event (July 2021).[B] Orthophoto of the VFS and the contributing agricultural area (2019).Green dots indicate the sampling points; red dots the actual field/VFS border.[C+D] Detailed view of deposited sediment in the VFS (July 2021).[E] View from the field into the VFS during sampling (November 2021).
Fig. A4 Site PL. [A] Situation after a heavy rainfall event (July 2021).[B] Orthophoto of the VFS and the contributing agricultural area (2017).Green dots indicate the sampling points; red dots the actual field/VFS border.[C] View from the field into the VFS during sampling (November 2021).[D] Detailed view of the erosion pathway and deposited sediment.[E] Overview of site PL (November 2021).
Fig. A6 Site ME4.[A] Situation after a heavy rainfall event (July 2021).[B] Orthophoto of the VFS and the contributing agricultural area (2017).Green dots indicate the sampling points; red dots the actual field/VFS border.[C] Detailed view from the field edge into the VFS showing the erosion and runoff pathway (July 2021).[D] Detailed view from the VFS into the field showing the runoff pathway (November 2021).[E] Orthophoto of site ME4 with visible erosion pathway (October 2019; © Google Earth).Note, that the VFS used as an agricultural field until approximately one year before sampling.
Fig. B1 Site SB.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).

Fig. C1
Fig. C1 Site AM.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).

Fig. D1
Fig. D1 Site HO.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).

Fig. E1
Fig. E1 Site PL.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).

Fig.F1
Fig. F1 Site ME3.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).

Fig. G1
Fig. G1 Site ME4.Distribution and concentration of all analyzed physical and chemical soil parameters.Boxplots integrate over all depth classes.Brown -Field, Green -VFS.White dots indicate the mean, black lines the median, the boxes the 25 and 75-percentiles, the whiskers the 5 and 95-percentiles, and the diamonds outliers.For details about parameters see the main text and Ramler & Strauss (2023).