plowpan

   [ soil survey ]

   A relatively thin, but highly compressed soil layer at the depth of tillage (e.g., 8-25 cm), largely the result of driving tractor wheels in a furrow while plowing. A plowpan can dramatically reduce vertical root penetration, water percolation, internal gas exchange and subsequent crop growth; sandy loam soil textures are particularly susceptible.

   SW & GSST