Soil value (German:Bodenwertzahl) orBWZ is a comparative assessment ofsoil quality used inGermany. It is determined fromsoil sampling data and ranges from 0 (very low) to 100 (very high).
According to the Geological Service of the state ofNorth Rhine-Westphalia, the soil value ofarable land is based on a field assessment framework which combines an assessment of soil type, soil condition (soil development) and the parent material of which the soil is composed. The result, the soil value, expresses the relative net income that, under normal and proper management, is determined only by the profitability of the soil. Additions or deductions in this value to take account of variations in yield due to terrain and climate (e.g. average annual temperature) give the field value (Ackerzahl).[1]
The following colour scheme is used referring to the soil quality for certain ranges of values:[1]
| Soil quality | Range of values | Color |
| Very poor | 0–18 | brown |
| Poor | 18–35 | red |
| Medium | 35–55 | orange |
| High | 55–75 | yellow |
| Very High | 75–100 | green |
The values exhibited by different types of soil are:[2]
| Type of soil | Range of values |
| Sand | 0–11 |
| Sandyloam | 11–30 |
| Heavy toclayey loam | 31–50 |
| Loam, partly with loess covering | 51–70 |
| Loam with loess covering | 71–90 |
| Loess | 91–100 |
As a yardstick for soil quality, a "Reich Standard Farm" was set up during theThird Reich in the parish ofEickendorf in theMagdeburger Börde, an exceptionally rich arable region. During the Reich Soil Assessment (Reichsbodenschätzung) following the Soil Assessment Act in 1934 a soil value of 100 was established in the leading Reich farm ofHaberhauffe/Jäger. It was the basis of comparison for the tax rating of farms in Germany. Since this farm was no longer available for comparisons withinWest Germany after theSecond World War, a farm inMachtsum nearHarsum in theHildesheim Börde was designated as the Federal Standard Farm. During later measurements, an even higher value of BWZ – 102.8 – was measured in Mölme, about 20 km east of Hildesheim within the municipality ofSöhlde. It is the highest value ever recorded in Germany.
Another measure, the field value (Ackerzahl), is derived from the soil value, taking account of other factors such as climate and location e.g. along the edge of woodland.
