Business Model Climate Farming ...
is the headline of the trade press. Of course, we don't begrudge any farmer expanded sources of financial income. And maybe it also helps to polish up the bad image of agriculture, which is mostly created by the media. On closer inspection, however, one realises that an expectation is being raised here that cannot be anchored in reality. It is to be expected that resourceful businessmen want to establish a flourishing business as free riders with the certificate trade.

My recommendation: Hands off!

Prof. Körschens, together with the Förderverband Humus e.V. (Humus Promotion Association), takes a stand on this from an arable farming perspective. This group of scientists has devoted almost their entire life's work to the establishment, investigation and evaluation of long-term experiments on humus. See also www.agrarfakten.de
Peer Leithold

Prof. Dr. habil. Dr. h. c. Martin Körschens,
Förderverband Humus e. V.
Goethestadt Bad Lauchstädt
e-mail: m.koerschens@t-online.de

No one doubts that the climate is changing, and it has changed several times over the past millennia (cf. DAHM et al, 2015, et al.).  For example, less than a thousand years ago Greenland was still a "green country".

There are different opinions about the causes of climate change. The IPCC assumes that a man-made increase in the atmospheric
CO2 concentration in the atmosphere is the cause. There is obviously insufficient evidence for this. Irrespective of these different opinions, scientists, politicians and business people see the soil, i.e. humus, as a carbon sink and thus the possibility of simply storing the excess CO2 from the atmosphere in the soil.

Numerous speculations and misconceptions surround this problem. For example, the EU (in a Communication from the Commission of the European Communities to the Council, the European Parliament, the Economic and Social Committee and the Committee of the Regions, 2003) claimed that "soils with an organic matter content of less than 3.6% are in the preliminary stages of desertification." According to this view, Europe is already a desert. Yet in this "desert", yields have multiplied over the past hundred years. Thanks to the successful work of farmers and agricultural research, today more than 10 t/ha of winter wheat are harvested annually in some places, and soil fertility has increased significantly in this "desert".

The possibilities for increasing the humus content are very limited. The differentiation of humus into nutritive humus and permanent humus has been known since time immemorial, but today it is ignored and almost exclusively the total humus content is evaluated, which inevitably leads to irritations and misinterpretations. Only the nutrient humus can be influenced in measurable periods of time. The content of permanent humus-C (arable land) is predominantly between 0.3 and 1.5 % Corg. The nutrient humus-C that can be influenced by management measures in the tillage horizon is on average 0.3 % and often accounts for less than 0.2 % Corg, i.e. about 10 t/ha (in 32 of 68 Daufeld trials, mainly on sandy soils) and rarely exceeds 0.5 % Corg. (only in 11 of a total of 68 permanent field trials).

Excessive humus contents reduce the utilisation of soil N and increase atmospheric pollution with CO2, N2O and CH4.

90 % of the organic primary substance (OPS) added to the soil, based on the initial substance of plant biomass, is re-mineralised and returned to the atmosphere (HAIDER, 1997, KÖRSCHENS, 2017 et al.), i.e. for an increase of the Corg content in the soil by only 0.1 %, an application rate of >100 t/ha plant dry matter is necessary in the long term (cf. www.agrarfakten.de).

The French government's initiative "4 0/00 annual growth of the C stock" has no chance, because with a C accumulation of only 10 % annually, utopian amounts of additional plant dry matter would have to be applied to the soil. If we assume the figure of 1.2 billion t C given in the initiative, this would be at least about 500 kg C/ha annually x 10 = 5 t OPS-C = 12.5 t/ha plant dry matter (40 % C in the dry matter), i.e. a complete harvest.

This largely eliminates the discussion about "carbon sequestration", possibilities for which are limited to a few exceptions. Moreover, an increase is neither beneficial for yield formation nor for the environment.

In the media, simple ways of saving the climate are presented, mostly by laymen. For example, SCHEUB/SCHWARZER (2018) formulate in the book "The humus revolution": "A global humus increase of just one percentage point could take 500 gigatonnes of CO2 out of the atmosphere. This would bring the current CO2 content of the air to a largely harmless level".

The amount stated here is roughly a hundred times what the French government's initiative proposes. Such ideas about saving the climate, as also advocated by RAGGAM (2008) in Austria and disseminated on television, belong to the realm of fantasy, lack any expertise and only serve to attract attention. That everything is done to maintain and increase soil fertility and thus to increase yields is self-evident and has always been done by farmers. But one should not be under the illusion that a significant increase in the carbon content and thus a reduction in the CO2 concentration of the atmosphere can be achieved and thus that the future of our planet is in the hands of the farmers. Being a farmer is a demanding and multifaceted profession. But no farmer would think of advising a doctor how to perform a heart valve operation. No doctor would think of suggesting to an engineer how to build a spaceship. Only some politicians or unskilled workers are so presumptuous as to want to tell a farmer how to cultivate his land.