The loess soil - fertile and fragile

Important reasons for the high fertility of a loess soil are the good rootability of the loose rock and the favorable mineral composition for plant nutrition. In addition, loess soils have coarse pores for sufficient aeration of plant roots in the event of excess water. At the same time, they have medium pores for storing a large water supply. Both are important properties of agricultural soils during extreme precipitation and long dry periods. The fine loess material can be very easily eroded by wind or water in the absence of protective vegetation. On slopes, loess soils are therefore particularly vulnerable to erosion. Due to the soil properties, they are also sensitive to compaction.

Where do loess soils occur?

In Switzerland, loess soils occur mainly in the flat-wavy landscapes in the north around Basel, Baden and Schaffhausen. Loess forms the parent material for particularly fertile soils. When dry, loess feels like flour and appears visually light yellow. It consists of silt, carbonates, clay minerals and very fine sand. During and after the last ice ages, loess was blown out of areas with little vegetation, transported by the wind and deposited as loose rock. Such loess deposits can range in thickness from a few decimeters to several 100 meters. They extend in Eurasia from France over the northern edge of the Central European low mountain ranges to the Ukraine and China.

Multifunctional floor

Soil fertility for food production is only one aspect of the multifunctionality of soils. In addition to the production function, they fulfill other important services for humans and the environment. This is assessed through various "soil functions". In May 2020, the Federal Council issued the "Soil Strategy Switzerland". In it, the vision is formulated "to shape the use of soil in such a way that the functions of soil are preserved in the long term, so that future generations can also benefit from the diverse services". With several Projects and measures such as the Cantonal Soil Monitoring Office (KABO), the Canton of St.Gallen contributes to this vision and is actively committed to preserving the functions of the diverse soil types.

Source: Canton St.Gallen

What is the function of the soil?

Soils fulfill other important services for humans and the environment in addition to their production function. This is expressed and evaluated by different "soil functions".

• Habitat function: Soil is a habitat for soil organisms and plants and maintains biodiversity.
• Regulatory function: Soil regulates water, material and energy cycles by storing and transforming.
• Production function: Soil produces biomass, which is used for the production of food for humans or as fodder for animals. Likewise, soil provides renewable raw materials such as wood or fibers.
• Carrier function: Soil is building ground.
• Raw material function: soil contains raw materials, water and geothermal energy.
• Archive function: Soil preserves information of natural and cultural history.

Source: Soil Science Society of Switzerland