Soil map of Lower Saxony 1: 50 000 — Local relocation potential — Soil water exchange frequency (1991-2020) (WMS Service)

The map shows the average local relocation potential for non-absorbable substances (also exchange frequency of soil water per year) for the 30-year period 1991-2020. With the help of the exchange frequency (AH) of soil water, the local relocation potential for non- or weakly absorbable substances can be described. This includes nitrate, among other things. The AH describes how often the soil solution is exchanged in the effective root zone in the course of leachate displacement. The lower the water storage and retention capacity of a soil, the greater its frequency of exchange of soil water. The variables of the soil water balance describing the exchange frequency, i.e. the “field capacity in the effective root space” and the “leach water rate”, form the characteristic values for the water storage capacity of a soil. Statements on the concentration and cargo of non-sorbable substances cannot be mapped with the method. For nitrate, deposition, denitrification and mineralisation are not taken into account. Depending on the location, they can have a significant impact on nitrate availability and concentration in leachate. For example, in marches, the denitrification performance is particularly high due to the high proportion of organic matter. Since the validity ranges of the calculation formulas are restricted by the slope inclination, no results are provided for arable areas > 3.5 % slope inclination, nor for grassland and forest > 18 % slope inclination. The exchange frequency per year is shown in classified form. This parameter describes the local risk of relocation.