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Berlin Environmental Atlas

01.12 Soil Functions (Edition 2002)

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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 the soils for silvicultural use is not evaluated 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 basic nutrients (Ca, K, Mg) and of carbon, 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 the Nutrient Storage Capacity/ Pollutant Binding Capacity (01.11.6). The evaluation of the site, broken down into "low", "medium" and "high" in levels 1 -3, can be seen in Table 1.

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Figure 1: Plan for the evaluation of the yield function for cultivated plants

Table 1: Evaluation of the yield function for cultivated plants due to the sum of the evaluations of the criteria Water Supply and Nutrient Storage Capacity / Pollutant Binding Capacity
Sum of the evaluation of the criteria Water Supply and Nutrient Storage Capacity / Pollutant Binding Capacity Yield function for cultivated plants
  Evaluation Designation
2 1 low
3 1 low
4 2 medium
5 3 high
6 3 high
Table 1: Evaluation of the yield function for cultivated plants due to the sum of the evaluations of the criteria Water Supply and Nutrient Storage Capacity / Pollutant Binding Capacity (Lahmeyer 2000 and Gerstenberg/Smettan 2001)

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 gley-bog associations with a high content of organic substance and good water and nutrient supply. In addition, there are limey gyttja soils and, on the plateaus, pale leached soils and sandy-wedge rusty soils from glacial till with inlayed sand. However, no large coherent areas are formed.
Small-scale nutrient-rich alluvial bogs in glacial-stream channels and a few calcareous and nutrient-rich gley associations in valley-sand sections attain a medium evaluation. On the glacial till plateaus with near-natural uses, the bulk of this evaluation class is para-braunerde and pale leached soils, associated with sandy-wedge braunerde, sand wedge rusty and rusty soils.

The reason for the high share of sections with a low yield functions is the nutrient-poverty and frequently bad water supply of the sandy soils and the restricted water supply for the groundwater-remote loamy plateau soils. Thus, sections with silvicultural use are for example frequently characterized by sandy and low-nutrient sites. They are large coherent complexes concentrated in the outlying areas.
The soil associations of the center are usually characterized by anthropogenic deposits. They are also characterized by a low yield potential.

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