Het Dollardgebied : bodemkundige en landbouwkundige onderzoekingen in het kader van de bodemkartering

The soil survey of the Dollard area was made to solve certain agricultural problems, especially those arising in the older polders. For these studies the value of the soils for different crops was assessed.The region consists of Pleistocene and Holocene sediments. Its geological history could be compared with those of the other marine landscapes. Dating of the Holocene sediments proved that the first incursion was slightly younger than in the west of the Netherlands. In the 15th and 16th century the sea inundated a vast area of peat and two types of sediments were deposited. After the 16th century successive dikings took place, giving the Dollard its final form.Loss of CaCO 3 was 1 % in 100 years, a lower figure than stated by older theories, which supposed a uniform CaCO 3 content for newly reclaimed polders.The suitability of these soils was studied by the 'determination-of-arrangement' method; in this method soils were grouped in sequence according to suitability for a range of crops, allowing also for non-soil factors. Drainability and possibilities of soil improvement were studied and mapped