Podzolization is a process of accumulation in soil

Podsolization is a complex soil formation process by which dissolved organic matter like silica and ions of iron and aluminium, released through weathering of various minerals, form organo-mineral complexes and are moved from the upper parts of the soil profile and deposit in the deeper parts of soil.
The surface soils have relatively infertile and high in silica because of the process of podsolization.