Humus is almost as fossil as brown coal

But we can restore it regeneratively – with many advantages

For over 7000 years, long before the discovery of the brown coal, humans have been exploiting soils and forests non-regeneratively and releasing additional CO₂ as part of the carbonisation strategy. Through ever better and deeper ploughing, the quasi-fossil nutrients (especially nitrogen) in the humus were released and the humus content in many soils was reduced from an average of 3 % to around 1.5 %. For a long time, this provided a lot of fertiliser to feed mankind, but is now reaching its limits. Many soils have already been irreversibly damaged, but even more soils are now in great need of regenerative cultivation.

At 2.1 billion tonnes of CO₂ per year, agricultural soils are the second largest source of CO₂ emissions from agriculture, just behind deforestation.

As part of the generally necessary decarbonisation of all sectors, not only must nitrogenous fertilisers now be produced from green electricity/hydrogen instead of coal and natural gas, but the soil must also be rebuilt and at least partially fertilised with regeneratively produced humus. This is exactly what regenerative agriculture does with cover crops and usually greatly reduced tillage.

Soils are a wealth and must be cared for. However, they also offer a great opportunity to make an important positive contribution to the regenerative storage of CO₂. This is because we can no longer get the burnt brown coal back into the open-cast mines.

Arable land stores over 140 billion tonnes of carbon in the top 30 cm of soil. Through practices such as tillage, an estimated 78 billion tonnes of soil organic carbon (SOC) have been lost since the industrial revolution, equivalent to 286 billion tonnes of CO₂. (Carbon in Cropland Soils) For comparison, annual global CO₂ emissions 38 billion tonnes of CO₂ (Broken Record Temperatures hit new highs, yet world fails to cut emissions (again))

Studies show that consistent cultivation of cover crops, where feasible in combination with direct sowing, can turn the soils of CO₂ emitters into carbon sinks. CO₂ is then additionally removed from the atmosphere using regenerative energy from sunlight. (When does soil carbon contribute to climate change mitigation?)

Increasing the organic carbon content in soils by 0.27% to 0.54% in the top 30 cm of the world’s cultivated areas could sequester 0.90 to 1.85 billion tonnes of carbon annually for at least 20 years. This corresponds to 3.3 to 6.8 billion tonnes of CO₂ per year. (The international “4 per 1000” Initiative)

The intensive use of green manure and direct sowing plays an important role here. It can bind 0.7 to 1.6 billion tonnes of CO₂ per year on up to 25 % of the world’s cultivated areas. (Climate Change and Land) For comparison: Emissions from road transport in Europe in 2022 0.74 billion tonnes of CO₂ (Straßenverkehr: EU-weite CO₂-Emissionen seit 1990 um 21 % gestiegen)

However, like any investment in the future, the soil and the humus in it must be well cared for. That is why a return to the plough is not an option. Depending on soil type and cultivation, soils have a binding potential of 1 to 4 tonnes of CO₂/ha per year. However, a single ploughing of a no-till field can release up to 10 t CO₂/ha and thus destroy the storage effort of many years. (Loss of soil organic matter upon ploughing under a loess soil after several years of conservation tillage)

This example shows the importance of efficient plant control without ploughing and with minimised soil movement. Furthermore, ploughing/tillage is the most energy-intensive agricultural practice (with the exception of flaming in organic farming).

In order to decarbonise agriculture and make it an active climate improver in cultivated landscapes, some major changes will be necessary, but many farmers have already begun to make them. The side effects not only of ploughing but also of glyphosate for soil life, biodiversity and general health will always have to be considered.

Farmers need new methods to meet the rapidly growing demands of climate protection and biodiversity. At the same time, they must always provide the world’s food supply, regenerative organic raw materials and also some fun with the luxury foods and drinks. As part of sustainable agricultural technology innovation, crop.zone supports farmers with food production as well as the Green Deal with society. Because we need both – without compromise.