The mineral and organic materials in drainage ditches, when stable, may form soils as defined as materials that can support rooted vegetation or form horizons through processes of soil formation. Vegetation in ditches increases sediment retention, cycles nutrients, and promotes the development of soil structure. Soil-forming processes such as horizon formation, biogeochemical cycling, structure formation, and faunal activity may affect the environmental quality of a ditch and its role in mediating the quality of overlying waters. In this paper we provide an overview of soil formation and biogeochemical processes that operate in ditches and discuss the role that these processes have in the mitigation of nutrient and pollutant losses from agriculture. We propose that ditch soil formation is a function of climatic temperature regime, organisms, topography (including the topography of the ditch and the surrounding landscape), bathymetry, flow regime, parent material, time, water column attributes, and catastrophic events. Management procedures that encourage ditch vegetation, such as targeted clean-outs and gradual inundation, may increase the stability and ecosystem services of ditch soils. Site assessment and modeling of ditches may be improved by integrating information about ditch soils.