The National Soil Monitoring Network NABO assesses and documents the soil quality at about 100 sites. The long-term monitoring facilitates an early detection of undesirable developments. Since 1985, this reference network has served the impact assessment in environmental protection. It focuses specifically on substance accumulation in the soil, soil compaction and soil biology.

Figure: Distribution of NABO sites according to use category.

Roughly half of the sites under long-term monitoring are used for intensive agriculture, including arable farming, vegetable farming, fruit farming and viticulture, or as intensively used grassland. One-fifth is located in extensively used areas such as pastures and alpine pastures, and about one-third in forests. In addition, two sites have been established in city parks.

The selected NABO sites represent a combination of land use, soil type, geology, altitude and other site properties that are typical of Switzerland. The monitored areas are neither marked nor closed off or otherwise protected so that the assessed conditions of agricultural or silvicultural use are as close to the actual situation as possible. Buried magnets allow an exact localisation of the 10 m x 10 m sites, guaranteeing the continuous sampling in the same areas.




Sampling with Reference Standards

During each sampling for the National Soil Monitoring Network, relevant physical parameters are also recorded. Thus, the current conditions can be compared with those from previous samplings. The current soil condition directly influences properties of the soil samples. Thus, systematic errors can be avoided and unusual conditions detected.


Localisation of Compaction Zones

Soil consists of a solid structure and a cavity system: The solid material is composed of large and small minerals and organic substances. Inappropriate management destroys the soil’s three-dimensional integrity and leads to compaction, with negative impacts on the ecological properties. The National Soil Monitoring Network NABO thus intends to determine the extent of compacted zones and the degree of compaction.


Organic matter: Soil Data from over 30 Years

Numerous soil functions are significantly characterised through soil organic matter: It is a central regulating parameter for soil-dwelling organisms, plants and farmers. Furthermore, soils as a whole store almost as much CO2 as the oceans. The National Soil Monitoring Network NABO now extends the sampling of organic content from the topsoil to the deeper soil layers.


Nutrient Content in Agricultural Soils

The input of nutrients via fertilisation of agricultural soils ensures high crop yields. It is the only way to produce the calories required for human and animal nutrition. The National Soil Monitoring Network ensures that the nutrient availability in the soil remains at a balanced, sustainable level, not too high and not too low.


How the Monitoring Began: Heavy Metal Contents

Heavy metals were among the first substance groups identified as pollutants that can impact soil fertility. Thus, the assessment of heavy metal contents in soils is the first item in the statutory mandate of the National Soil Monitoring Network NABO. The results from the last 30 years confirm that today far fewer heavy metals are introduced into the environment than in the past.


PAH, PCB and PPP as NABO Priorities

Since its foundation, the National Soil Monitoring Network has had the statutory duty to estimate the risk that organic pollutants pose to soils. Therefore, from the beginning, polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) have been assessed. Today, the assessment programme also includes plant protection products (PPP).