This is also shown by the "Soil Condition Survey Agriculture" from 2018. According to it, an average of 0.21 tons of organic carbon per hectare of arable land topsoil will be lost in Germany over the next 10 years if nothing changes in the management of the land. Topsoil is the mixture and combination of humus, i.e. organic substances with mineral components.

Humus as a carbon store

For this soil condition survey, the scientists took more than 12,000 soil samples across Germany between 2012 and 2018 and analyzed them.

Both oxygen supply, humus formation and carbon stocks were measured at the sites. The results clearly showed that a total of around 2.5 billion metric tons of carbon is stored in the uppermost meter of agricultural soils. This means that almost twice as much carbon is stored by humus than by trees in German forests.

Threat of humus depletion

But humus stocks are in danger of dwindling, the Soil Condition Survey found. "For a ten-year period and assuming long-term constant management and climate conditions," they predict a loss of organic carbon amounting to -0.21 tons of organic carbon per hectare per year. Since humus is formed by biomass, such as straw or organic manure, which are rarely available on agricultural land today, less and less humus is formed.

At the same time, fewer deep-rooted plants, such as clover grass or alfalfa, are cultivated, which are usually only found on organic farms. Yet alfalfa is one of the crops that are extremely important for humus formation.

Measures of the report

The report also lists measures to store existing humus reserves sustainably in order to promote humus growth. One of these is the preservation and development of green spaces, as these can serve not only to protect water and erosion, but also to build up humus, as you can read here.

At the same time, fertilization with organic means should be promoted, with e.g. manure, slurry or digestate. Organic fertilization can contribute significantly to the build-up of humus with 2 to 22 tons per hectare more carbon in the long term compared to arable soils without organic fertilization. This can be implemented, for example, by supporting animals on the land, as here with the help of a cattle farm on the land. The report particularly emphasizes the benefits of organic farming. 

Here, not only organic fertilizers are used, but also humus-increasing crops are cultivated.

Use of synthetic chemical crop protection products 

Sales of synthetic chemical crop protection products have remained stable for years. But to date, there are hardly any accurate statements on the current consumption of chemical-synthetic crop protection products in fields. On the one hand, this is due to the difficulty of precise investigation. Up to now, samples have increasingly been taken only at random and at irregular intervals. On the other hand, only approximate consumption can be inferred from sales, since crop protection products are often used and stored over several years. In addition, agricultural locations in Germany are subject to different conditions and have different needs, which means that protective agents are also used in a wide variety of ways. On average, the Federal Environment Agency calculates that 8.8 kilograms of crop protection products or 2.8 kilograms of active ingredient are used annually per hectare of cultivated land. 

The Report also took a closer look at the use of crop protection products. To date, only a few scientific studies have examined the impact of their use in organic and conventional agriculture, mainly due to the extensive ban on plant protection products in organic farming. Special focus was placed on the occurrence of earthworms, as they indicate a fertile and biologically active soil. The observations clearly showed that conventionally farmed areas had low earthworm abundance, as pesticides can have negative impacts on ecosystems or even be toxic. At the same time, when pesticides were not used, there was a direct positive influence on animal and plant diversity.

Source: (in German) 

Thünen Institute for Agricultural Climate Protection