De bodemgesteldheid van de Haarlemmermeer

The Atlantic marine incursion (5000-2300 B.C.) deposited sands and clays in the western Netherlands at a level about 4 metres below mean sea-level which could be easily studied in the Haarlemmermeer Polder. Some incursions and their sediments were traced in the terrain (Old Holocene sand, Hoofddorp deposits, Old Marine clay and Beinsdorp deposits); a small regression period allowed soil formation (decalcification on the Hoofddorp deposits). In the Subboreal and Subatlantic period, peat started to grow on top of the marine deposits, interrupted by marine incursions; in Medieval times the peat was eroded and three lakes were formed, which afterwards coalesced into one great lake. This lake threatened to destroy the central part of Holland together with the town of Amsterdam and was finally pumped out and reclaimed in 1853. Granular composition and CaCO ₃ content determined suitability for crop production.The eroded peat was deposited as peat detritus in many places. There the topsoils were black and N manuring was not necessary, because of good nitrification. Sugarbeet produced less sugar on these soils.Apart from this, cat clay formation (causing low pH values) and seepage (mainly saline) were studied.Often deep trenching or deep ploughing was necessary to get a calcareous topsoil.