Soil rating — Nitrate leaching hazard/soil water exchange (NAG), rated nationwide

Soil water exchange is a characteristic for assessing the soil as a filter for non-absorbable substances and identifies the risk of relocation for non-absorbable substances such as nitrate (nitrate leaching risk). The nutrients remain almost completely in dissolved form in the soil water and are relocated with it (soil water exchange). The risk of relocation is high in soils with low water retention, high precipitation and low evapotranspiration. The higher the soil water exchange is the higher the risk of relocation, because the exchanged soil water leaks with the nitrates dissolved in it. Soil water exchange is used to evaluate a natural soil function in accordance with Section 2(2) of the BBodSchG, namely in accordance with point 1.c) as a degradation, balancing and building-up medium for material effects on the basis of the filter, buffer and substance conversion properties, in particular for the protection of groundwater. The criterion chosen for this purpose is the retention capacity of the soil for non-sorbable substances with the characteristic value of soil water exchange. The maps are available for the following scale levels: — 1: 1,000-10 000 for high-resolution or parcel-sharp planning, — 1: 10,001-35,000 for municipal planning, — 1: 35.001-100,000 for planning in larger regions, — 1: 100.001-350,000 for nationally differentiated planning, — 1: 350,001-1000,000 for nationwide to nationwide planning. In this representation, the soil water exchange is classified uniformly throughout the country. Under the title “Soil assessment — Nitrate leaching hazard/soil water exchange (NAG), regionally assessed” there is also a nature-specific classification of soil water exchange, which presents the soil water exchange more regionally differentiated.