Preferential Flow and Nutrient Transport in Structured Agricultural Soils: A Systematic Review of Experimental Evidence and Modelling Approaches

Abstract

Understanding water dynamics and nutrient transport in structured soils remains a critical challenge in hydrology, particularly due to the influence of preferential flow pathways. This systematic literature review synthesises evidence from 47 studies identified through screening 770 papers by title, abstract, and full text using a PRISMA-based workflow. This review only focused on eligible studies investigating water flow, solute transport, or modelling approaches in structured soil, while studies without an experimental or modelling component were excluded. This review included 39 studies, coupled with 25 and 28 studies using field, laboratory, and modelling approaches, to analyse preferential flow and nutrient transport. The most common method for field experiments is soil physical measurement (42%), whereas HYDRUS (28%) is the primary tool used in modelling approaches. Despite advances in physically based modelling, accurately representing preferential flow remains challenging due to limitations in model conceptualisation, parameterisation, and the representation of spatial and temporal soil heterogeneity. Modelling strategies such as dual-domain formulations and inverse modelling improve representation but introduce additional complexity and uncertainty. The synthesis highlights a critical gap between experimental evidence and model representation, emphasising the need for improved integration of soil structural dynamics and non-equilibrium transport processes in hydrological modelling.