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Berlin Environmental Atlas

01.12 Soil Functions (Edition 2006)

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01.12.2 Yield Function for Cultivated Plants

Description

The yield function and efficiency of the soils for cultivated plants describes the potential of the soils for suitability for agricultural and/or horticultural use and production. The suitability of soils for forestry use is not assessed here.

The yield function depends on the respective site conditions of a soil. These are essentially determined by the soil qualities, especially by the local water and nutrient balance. The water supply is determined by the storage capacity of the soils and any additional water supply for the plants from the groundwater, due to capillary rise. Loamy and/or groundwater-proximate sites are therefore considerably better supplied with water than sandy and/or groundwater-remote sites. The nutrient supply is closely connected with the thickness of the humus layer, the content of organic substance and the type of soil.
A well-developed humus cover constitutes a considerable nutrient reservoir, both of alkaline nutrients (Ca, K, Mg) and of nitrogen and phosphorus. Loamy soils are better provided with minerals than sandy soils, and can moreover hold and store the nutrients. This quality is taken into account in the evaluation by the consideration of the cation exchange capacity (KAKeff) of the soils which, however, reflects only the supply of basic cations. No restriction of rooting capacity by hardened horizons and adjoining solid rock occurs in the Berlin area. Nor is any distinction by relief required, since it does not vary strongly in the Berlin area, even over large expanses.

Methodology

The evaluation as a habitat for cultivated plants is accomplished on the basis of the sum of the point count achieved for Water Supply ascertained at the site, and for the Nutrient Supply of the topsoil (cf. Map 01.11.7). The evaluation of the site, broken down into levels 1-3 for "low", "medium" and "high," is shown in Table 1.

Diagram for the evaluation of the yield function of cultivated plants
Fig. 1: Diagram for the evaluation of the yield function of cultivated plants

Tab. 1: Evaluation of the yield function for cultivated plants, based on the sum of the evaluation of the criteria water supply and nutrient supply
Sum of the evaluations of the criteria water supply and nutrient supply Yield function for cultivated plants
  Evaluation Designation
2 1 low
3 1 low
4 2 medium
5 3 high
6 3 high
Tab. 1: Evaluation of the yield function for cultivated plants, based on the sum of the evaluation of the criteria water supply and nutrient supply (Lahmeyer 2000 and Gerstenberg/Smettan 2005)

Map Description

The yield function of the Berlin soils attains an evaluation of "high" in only a few cases. These are primarily groundwater-proximate sites with gleyic bog associations with a high content of organic substance and good water and nutrient supply. In addition, there are lime-mud soils and, on the plateaus, luvisol and arenic cambisol from boulder marl with inlayed sand, provided that they show high humus content. Since the humus contents vary depending on use, the yield function for cultivated plants also depends greatly on the use form (cf. Figure 2); also, no major coherent areas are formed.

Evaluation of the yield function for cultivated plants per use class (incl. impervious sections without streets and waters, not all uses, are represented)
Fig. 2: Evaluation of the yield function for cultivated plants per use class (incl. impervious sections without streets and waters, not all uses, are represented)

Excel
[Statistical base of Figure 2 is also available as Excel-File (MS-Excel is required).]

Small-scale nutrient-rich alluvial bogs in glacial-stream channels and a few calcareous and nutrient-rich gley associations in valley-sand sections receive a medium evaluation. On the boulder marl plateaus with near-natural uses, the bulk of this evaluation class is luvisol and podzoluvisol, associated with arenic cambisol, dystric cambisol and cambisol.

The reason for the high share of sections with a low yield functions is the nutrient-poverty and frequently poor water supply of the sandy soils, and the restricted water supply for the groundwater-remote loamy plateau soils. Thus, sections with forestry use are for example frequently characterized by sandy and low-nutrient sites. They are large coherent complexes concentrated in the outlying areas of the city.

The inner-city soil associations are usually characterized by anthropogenic deposits. They are also characterized by their low yield potentials.

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