Note 118 — Chapter IV · NITRIFICATION.
Reading edition
In sixty-nine trials no failure to produce nitrification by seeding with soil from a depth, of 2 feet was experienced. Similarly in eleven trials only one failure took place with soil from a depth of 3 feet. With clay soil from a depth of 6 feet success took place to the extent of 50 per cent. No nitrification was obtained with clay from a depth of 8 feet. Entire failure was experienced with chalk subsoil. The process thus diminishes in activity the lower down we go.