What nutrients are missing in acidic soil?

Bavarian State Office for
environment

Soils are acid buffers. This is due to buffer substances such as carbonates, which keep the pH value almost constant in the case of acidic inputs. Why is Bavarian soils endangered by acidification?

causes

In Central Europe, most soils experience one weakness,natural acidification during soil formation. This happens through carbon dioxide (CO2) in precipitation, excretions from roots and leaching of buffer substances with the seepage water.

Industry, transport, agriculture and household fireplaces come across sour lookingNitrogen and sulfur compounds (SO2, NHx, NOx) in the air. The combustion of sulfur-containing energy sources such as lignite, for example, produces sulfur dioxide (SO2). The abrasion of car tires can also contain sulfur compounds. Nitrogen compounds such as ammonia (NH3) mainly get through intensive animal husbandry and Spreading of manure in the air.

Wherever in Bavaria low-base parent rocks like mica slate, granite and gneiss, so are the floors particularly sensitive against acidification and pollutants such as acidic nitrogen and sulfur compounds (SO2, NHx, NOx) endangered.

Forest with conifers; Photo: C. Bremer
Undergrowth of blueberries; Photo: C. Bremer

Conifers like spruce grow relatively quickly and provide regular, straight lumber. But: especially those Litter from conifers forms acidic support horizonswhich can only degrade soil life with great difficulty, which is why monocultures from conifers in particular intensify acidification.

consequences

Binding nutrients for plants and immobilizing heavy metals - clay minerals in particular do this in soils. But: Acidification destroys clay minerals. And with the clay minerals, the nutrients are also lost, many heavy metals become mobile and pass into the soil solution. The toxic effect can then be transferred to plants, soil life and groundwater, for example.

If there is a lack of nutrients, plants lose vitality on acidic soils. In addition, the Resistance to drought stress or pests.

The species composition can change in acidic soils: for example, earthworms cannot survive in soils with pH values ​​below 4. If there is a permanent lack of soil life, no more humus is incorporated into the soil or crumb structures - typical for humus topsoil horizons - are lost.

Soils can store rainwater in the pores for long periods of time. Without the binding clay minerals they disintegrate Aggregates the structure. Therefore dry acidified soils with destroyed clay minerals easily.

Scheme: Pathways in the acidification of soils

Protective measures

  • Calcium carbonates such as calcite (CaCO3) artificially brought to the fields. Such Limescale compensate for the loss of carbonates through seepage water and keep the pH value constant.
  • For ecological and economic reasons, amelioration is usually not done on forestry areas. But: a higher one Proportion of deciduous trees can, for example, deliver bases to the upper floor areas via the litter.

Spessart, Franconian Forest and Bavarian Forest: Risk from acidification

Examples of acidic soils in the Spessart, Franconian Forest and Bavarian Forest

In the Spessart, Franconian Forest and the Bavarian Forest, base rocks such as sandstone, mica schist, granite and gneiss are poor in base. The soils there tend to naturally acidify and are particularly drained sour lookingNitrogen and sulfur compounds (SO2, NHx, NOx) endangered.

In addition, parts of the Franconian Forest and Bavarian Forest record high annual rainfall, which accelerates the leaching of buffer substances with the seepage water. Some places look back on intensive, historical forestry for glassworks, charcoal burning and forest pasture.

In the Bavarian Border area with the Czech Republic Soil scientists at the LfU have investigated the acidification of soils under forests and forests in two cross-border areas EU projects examined.

Additional information

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