World Soil Museum adds 12 Dutch soil profiles to its collection

'Geestgrond' Sassenheim

A beautiful Podzol beneath an impoverished wood of pines and the soil profile of a bulb field form part of the World Soil Museum’s new collection, which comprises 12 typical Dutch soil profiles.

The ground beneath an impoverished wood of pines near Blitterswijck is a perfect example of an Albic Placic Podzol. And the soil profile of a bulb field near Voorhout shows what a major impact tulip growers have had on groundwater levels. These two soils form part of the World Soil Museum’s new collection, which comprises 12 typical Dutch soil profiles. After preparing to monolith they will further enrich the existing collection.

‘This is really a very exciting soil profile’, says Bas Kempen, researcher at ISRIC. He points to the  soil profile excavated last year from a river dune near Blitterswijck in the province of Limburg. ‘A Podzol with such a thick white layer is very rare.’ However, this soil type, formed on  dispersed river sand, is far from fertile. It only sustains a few miserable pine trees.

Haarpodzolgrond Blitterswijck

The World Soil Museum sought to augment its collection of 25 soil profiles from the Netherlands with this Albic Placic Podzol from Blitterswijck because it didn’t yet have such a fine example of this soil type. Albic Placic Podzols are mainly found in nature reserves such as the Veluwe, and in the provinces of Drenthe and North Brabant. They are characterized by an ash grey – in this case white – layer (Podzol translates as ‘ash’ in Russian). In this layer the dark, organic material has been washed away, along with minerals such as iron and aluminium. That is caused by the extreme acid formation in this soil type. The acid dissolves the minerals, which go on to form aggregates with the organic matter that can easily be washed away.

The museum already has several Dutch Gleyic Podzols profiles on display. In these, the organic material is not so much washed away by rain as by fluctuations in groundwater levels. The museum’s digital map table shows the distribution of Podzols throughout the world. They commonly occur beneath pine forests in Northern Russia or  Canada. And they also occur in the tropics. But if you look at the podzol profiles in the museum, from as far as Sweden, Zambia and Indonesia, then you will see that they can differ significantly from one another.

Terric Fluvic Anthrosol

The ISRIC  soil scientists also wanted to include an example of so-called Terric FluvicA anthrosol, a soil type formed in dune and beach sand and influenced in part by human activity. One such example of Terric Fluvic Anthrosol was excavated near Voorhout in the province of South Holland.At first sight the profile resembles a dull, grey mass. A closer look reveals that it is comprised of several distinct layers. At a depth of 55 centimetres one can discern a narrow, rust-brown streak caused by iron oxidation.

There are also soils, such as the recently prepared Umbric Gleysol near Wageningen, where the groundwater level fluctuates more. Such soils are characterised by a thick rusty layer because oxidation occurs particularly when water levels fluctuate. But in Voorhout, the bulb growers keep groundwater levels at a steady 55 centimetres -- the reason for the narrow rust-brown streak.

It’s a textbook example of a ‘man-made’ soil. For sand extraction the natural top layer is first excavated to a depth of half a metre above the level of the groundwater. That guarantees that the bulbs aren’t nestled in water. Subsequently the growers have fertilized and worked the remaining dune sand to create a topsoil that is ideal for cultivating world famous bulbs.

The deeper sea sand layer, characterized by narrow, dark layers, is still as it was. Those layers have been created by tidal flows, explains Bas Kempen. Spring tides and floods used to wash clay or peat onto the sea sand, and they have remained behind as black ribbons in the soil.

Calcaric Cambisol

A third newly-excavated Dutch soil type is the Calcaric Cambisol near Aalst. Calcaric Cambisols are rated among the best soils in the world. Such soil sustains the fruit orchards of the Betuwe region. Calcaric Cambisols are formed in river sediment and are made up of a mix of river sand and clay (sandy clay). Such soils have a high natural fertility and are well drained, while the sandy clay enables groundwater to inch up to a height of a metre and a half during the summer so minimising the risk of  desiccation.

Over the coming months the new profiles will be prepared and made into monoliths, fort display in the museum. Still on the museum’s wish list is a so-called ‘terp’ profile, a soil profile from one of the regions where buildings in low-lying areas were constructed on raised mounds or ‘terps’ to protect them from flooding. And the museum  would like  a ‘koopveengrond’, a soil type rich in organic material that is widespread in the western Netherlands. ‘Once we have a monolith of these, we’ll have the ten most common soil Dutch profiles in the collection,’ explains Bas Kempen.