Northill village lies mainly on Oxford clay overlying Kellaways beds. Patches of glacial gravel (till) and boulder clay are to the west of the village. The eastern and northern parts of the parish lie on glacial gravel, and alongside the Ivel are superficial deposits of first and second terrace river gravel and alluvium. Ickwell lies on Ampthill Clay. Around the village the soil is highly fertile, lime-rich, loamy and clayey with impeded drainage. The eastern area of the parish has soil of low fertility, which is freely draining and slightly acid with a loamy texture.