Drainage Ditch Soil Morphology and Mineralogy Influenced by Hydrologic and Soil Treatments

Abstract

Drainage ditch soils mediate nutrient and sediment cycling and transport from ditch-drained agroecosystems. Ditch management may influence the hydromorphology and mineralogy of ditch soils, which in turn may affect their capacity to serve as a nutrient sink. We assessed the effects of hydrologic and soil treatments on ditch soil morphology using mesocosms (15-cm inner diameter, 20–40 cm length) gathered before and after a dredging event. Hydrologic treatments were continuous saturation, continuous field capacity, and an alternating treatment. Soil treatments were organic soil addition, soil removal, and a control. Mesocosms that experienced continuous saturation developed yellower soil matrices and redox concentrations than other experimental mesocosms; this yellowing was interpreted as a loss of paracrystalline ferrihydrite and a retention of goethite. Iron-monosulfides and depletions were more abundant in mesocosms experiencing greater degrees of saturation. The loss of ferrihydrite may indicate reduced P sorption capacity. Colluvial or alluvial materials observed in post-dredged mesocosms indicate the potential of high sediment loss in periods following dredging before vegetation and soil structure establishment.