functional soil mapping: soil texture

Functional soil mapping concerning soil texture

The granulometric composition is one of the most important factors for classifying soil characteristics. Hydrological processes and factors (surface flow, perculation, ground moisture, ground water, plant avaiability, capillary flow, ...) and the soil erosion are dependend on this composition. .

The following maps being done by n-dimensional kriging are examples of "functional soil maps". They contain regionalized soil textures of the upper part of the soil horizon (point data) and local terrain factors "altitude above stream line" (area data). The soil profiles being descriptions of the land-evaluation exist for the entire farm land in Germany. The profile-descriptions were transformed into modern pedological language (usage) by the "Niedersächsisches Landesamt für Bodenforschung (NLfB)". Subsequently the soil types were calculated out of the percentage of sand, tilt and clay (granulometric composition -on an average) and seperately regionalized.

Although the distribute of space of the granulometric composition is dependent on many factors (bedrock, lateral translocation of the material) it is possible to gain plausibly regionalization results based on simple terrain factors. Evidently being an average when using digital terrain modells as resource of area data. It is planned to use further geo factors which are relevant for granulometric compositions (see above). This will also improve the results of the regionalization.

Unlike the usual soil maps our functional maps model the grain texture as a continuum which means the metric factors are calculated in every grid cell (with given cell size). Being closer to reality this clearly shows the advantage over the usual maps. Classification can process these factors without loss. Any classification of soil types (vary in different countries) can be done any time (easily).

Preview/ download	title/ explanation

	1) Regionalized sand-share of the uppermost (top) soil horizon The illustration shows the result of the regionalization which was done by n-dimensional kriging based on the profiles of the land-evaluation together with the complexe terrain-factor "altitude above streamline". Extremely plausible seems the big share of sand in the area of the bunter sandstone (geological epoch within the series of the German Triassic 232 - 225 * 10⁶ years before present) which decreasing downslope as well as the sandy spots in the eastern part of the map-section (compare with (2) silt-share). It is easy to overestimate the sand-share in the areal around the Papierberg (red areas) which are caused by the high sand-fill of the valley below this mountain and its high altitude above streamline. Whereas the underestimation of the sand-shares in the slope of the escarpment (cuesta) of the Göttinger Wald is due to the lacking profiles of the soil-eluviation in the Göttinger Wald (wooded or forested).
Use: in combination with the silt- and clay-shares (see below) this is the most important factor to estimate the soil erosion, the soil water balance, the yielding ability, etc.

	2) Regionalized tilt-shares of the uppermost soil horizon The distribution of the (mostly loess-derivable) tilt-shares show small spots of greater tilt-shares in the higher areas of the western map-section. In the eastern part there is a distinct increase of the tilt-shares down the valleys which are distributed to the different deposits and the dislocation during the loess-deposit.
Use: in combination with the sand- (see above) and clay-shares (see below) this is the most important factor to estimate the soil erosion, the soil water balance, the yielding ability, etc.

	3) Regionalized clay- shares of the uppermost soil horizon The comment will be complete with the clay-shares to be regionalized. Beside the explanations of (1) and (2) the following is worth mentioning. In the overflow of the "Röt" (clay) in the lower slope of the escarpment (cuesta) there are spots with grater clay-shares. This is due to the mingle with loess-derivable tilt-component and the heap of debris (shell lime stone) because of the (partly recent) solifluction in the area of the "Röt"-clay.
Use: in combination with the sand- and tilt-shares (see above) this is the most important factor to estimate the soil erosion, the soil water balance, the yielding ability, etc.

	4) Soil texture classes of the uppermost soil horizon out of the regionalized sand-tilt- and clay-shares Adding the shares of sand (1), tilt (2) and clay (3) can for instance produce a map with soil texture classes. The classification of the soil texture was done with the class-limits of the "Bodenkundliche Kartieranleitung" of the "Geologischen Landesämter der BRD" (4th edition, 1994) (instructions for pedological mapping). Only very few additions of the sand-, clay and tilt-shares show <90 % or > 110 % (declared as "not classified" in the map) which indicates the high quality of the regionalization.
Use: important factor to estimate the soil erosion, the soil water balance, the yielding ability, etc.

Functional soil mapping of the scilands GmbH are different to usual soil maps. Opposite to those our maps consider the functions and attributes of the soil being important with regard to the using. These informations are difficult to get out of usual soil maps. With the help of geostatistics we take the basic data (soil eluviation, DGM, ...) to produce unclassified data which are highly accurate. For detailled information please see the document "Functional mapping".