The role of phytolith formation and dissolution in controlling concentrations of silica in soil solutions and streams

This work accounts for the plateau concentrations of Si observed in laboratory equilibrations of Bs horizon soils, for the maximum Si concentration reported for B horizons in the field, for a deep sink for Si in Bs horizons, and for the fact that the concentrations of Si in soil drainage water and in streams all fall in, or below, the range expected for phytolith solubility. Concentrations of Si in surface horizons can exceed these levels during droughts. The common assumption that the concentration of Si in soil solution is a result of a dynamic balance between Si released by mineral weathering and that lost by leaching is untenable for Bs horizons.