Properties and development of soils on reclaimed alluvial sediments of the Humber estuary, eastern England

Sunk Island, an area of reclaimed estuarine alluvial sediments in the lower Humber estuary, provides a series of recent surfaces ranging from around 100 to 260 years old, upon which soil properties associated with soil ripening can be examined free from the disturbance of subsequent flooding and sedimentation. Within the first 100 years of pedogenesis, overall bulk density of the sediment has increased, and profile differentiation has resulted from structural development, organic matter accumulation and tillage. The original sedimentary structures of the soil have gradually become obscured and overprinted by ped and pore patterns related to wetting and drying, burrowing and root development. Aeration has accelerated organic matter decay and accentuated the difference between topsoil and subsoil contents. Variations in aeration and moisture content have resulted in mottling, which has become less prevalent as the soils develop. Properties such as available water content, organic C and cation exchange capacity (CEC) depend upon the grain size characteristics, in particular clay content. Exchangeable bases have been progressively removed, reaching a state of quasi-equilibrium within 150 years of reclamation. Crystallisation of goethite has extended progressively deeper into the profile through time, accompanied by a decrease in amorphous iron compounds.