Organic Phosphorus Can Make an Important Contribution to Phosphorus Loss from Riparian Buffers

Abstract

Preferential flow has different agronomic and environmental effects in various soils. The objectives of this study were (i) to quantify matrix and preferential flow and (ii) to assess the effect of organic amendments on flow dynamics in agricultural Vertisols. Dye tracing and isotopic analysis were used to infer soil water infiltration and mixing on two plots: one treatment (with liquid hog manure) and one control. Results showed infiltration depths reaching 64 cm for the treatment plot and 45 cm for the control. For both plots, matrix flow was only observed in the top 10 cm, whereas preferential flow extended beyond the tillage depth. Dye traces provided evidence of lateral infiltration across macropore–matrix boundaries, while post-experiment soil water averaged δ2H = -15.1‰ and δ18O = -118.9‰, hinting at old water mobilization via macropore flow. The potential impacts of these results on chemical transport should be validated across different soils and environmental conditions.