Plaggen soils in the Netherlands

Abstract

In the Pleistocene sandy areas of The Netherlands, Germany and Belgium there are soils which, for centuries, have been fertilized with a mixture of manure and sods, litter or sand. In this way the original soil has been buried under a humose sand cover of varying thickness. In The Netherlands there are more than 221,000 ha of land with a humose sand cover thicker than 50 cm, and more than 196,000 ha with a cover from 30 to 50 cm thick. Many of these so-called plaggen soils are very old; exactly how old, it is impossible to say, as the methods of investigation applied (calculation of the age from the thickness of the cover, and determining the age by the 14C- method) do not permit precise conclusions. However, with the aid of archeological, historical and toponymical data, it can be assumed that the building-up of many soils began more than a thousand years ago. The oldest plaggen soils are found on moderpodzol soils. These are soils in the sandy areas with a relatively high content of easily weatherable minerals. Plaggen soils are particularly found in those places where the ground water is within the reach of man, but where the chance of a too-high ground water level is slight. When the choice became more restricted, due to the increasing acreage of cultivated land, the reclamation of humuspodzol soils and hydromorphic sandy soils was undertaken in the same way. The specific demands made on the place of reclamation result in a fairly close relation between the places where plaggen soils occur and the geomorphology of the area. Plaggen soils have, of old, been mainly used as arable land. The degree to which they are suitable for this purpose depends on their chemical and physical properties. Prior to the introduction of commercial fertilizers, their chemical properties often left a lot to be desired. Particularly because of their favourable physical properties, they belong among the good arable soils of the West European sandy areas. According to the System of Soil Classification for The Netherlands, they are classified as “enk” earth soils if the humose topsoil is thicker than 50 cm. The “enk” earth soils are classified further into brown and black. Soils with a plaggen cover of 30–50 cm thick are classified according to the buried soil profile (e.g., a podzol). In the 7th Approximation, plaggen soils with a humose topsoil of at least 50 cm are classed as plaggepts, in the order of the inceptisols. The soils with a humose topsoil of less than 50 cm could under this system be classified as plaggic intergrades.