The European Union is in the process of financing two research programs with public funds developing a new tillage tool intended, according to its designers, to “store atmospheric CO₂ in the form of organic carbon in the soil”. The industry funded project recently appeared in the journal The Furrow (1) promoting deep tillage to fight climate change.
Agriculture specialists reading the article wonder about the ability of the “super-plough” to meet the ambition of carbon sequestration. We will try to answer this question by recalling the principles of this theory, and then by describing the effects of tillage tools on the soil.
The “4 per 1000” initiative: a consensus from COP 2015.
According to the International 4 per 1000 Initiative resulting from the 2015 Paris Climate Conference (2), the principles of carbon storage and release in agricultural soils are the subject of a very broad consensus in the international scientific community.
Photosynthesis allows chlorophyll in green plants to capture CO₂ from the atmosphere and integrate carbon with hydrogen, oxygen and nitrogen and other elements to form both above and below ground tissues.
Their dead tissues and the exudates of living roots are transformed, by chemical reactions in interaction with mineral substrates, and countless soil organisms that feed on them, from the most visible (small animals, insects, earthworms) to the most microscopic (fungi, bacteria, protozoa) into an organic complex, the Organic Matter or Humus of the soil, essentially composed of carbon and nitrogen, in a C/N ratio characteristic of the ecosystem (ratio decreases with more decomposition).
In an undisturbed soil the atmosphere is higher in CO₂ because the living organisms respire as they break down the organic matter. If soils are disturbed (tillage), oxygen is added to the system as well as the mixing of organic matter with organisms, which makes it easier for them to find new food. Tillage accelerates destruction of organic matter much like opening the door on a furnace.
Tillage also destroys the fungal hyphae that are both the early consumer of coarse organic matter as well as providing a nutrient rich, distributed network of hairs that act like a slow-release fertilizer. Tilled systems are predominantly bacteria populations and lose the benefits of diversity and nested nutrient cycles.
Soil is therefore a complex living ecosystem. It functions optimally when all its organisms find optimal stable conditions of food and habitat, first and foremost without exposure or mechanical disturbance, or at least as little as possible.
Modern 4 per 1000 agronomy employing sustainable practices disturbs the soil as little as possible to preserve its structural integrity, organic matter, biodiversity, and thus avoid tillage damage and degradation that enables processes such as water erosion and nitrate movement as well as greenhouse gas emissions (e.g. loss of nitrous oxide from heavily fertilized conventional tillage).
SCA (Soil Conservation Agriculture) vs Tillage Tools
Soil Conservation Agriculture (SCA) fulfills the specifications of the 4 per 1000 initiative combining, according to the FAO definition, the elimination of tillage tools (No-Till, Direct Seeding Systems, SD), the complete and permanent coverage of the soil and a diversity of plants in a mixture or successively in rotations.
On the contrary, tillage tools, plough or other, opens the soil and mixes it, adds oxygen and thus quickly oxidizes the organic matter releasing CO₂ and likely some nitrous oxide contributing to greenhouse gas emissions. The tillage will also mineralize nitrogen and other nutrients bound in the organic matter which can be washed away easily from the bare soil to add nitrates and other nutrients to water bodies.
Many studies around the world have shown the long- and short-term detrimental impacts of tillage on soil. Some studies have shown that complete inversion of crop residue by ploughs can store some organic matter at depth in specific geographies of cool temperatures and wet soils. The net effect on GHG emissions, biodiversity and ecosystems remains detrimental.
This is why the use of tillage tools is now recognized by the soil science community of the United Nations FAO Global Soil Partnership as the main factor in the degradation of agricultural soils, combining the effects of the decreased organic matter, loss of surface soil structure, loss of biodiversity, increased compaction and increased rainfall or wind erosion. According to the World Food Programme, this continued degradation of agricultural soils by out-of-date techniques is a threat to global food security.
It is only in the last sixty years or so that this thousand-year-old phenomenon of degradation of agricultural land by being exposed by tools of fire and iron has begun to be curbed by the implementation of Soil Conservation Agriculture. While it represents 12% of the world’s annual crops, SCA exceeds 50% and is growing rapidly on the South and North American continents and Australia regions that contribute the most to global food production. It remains below 5% on the other continents, with the exception of some African countries where it is developing rapidly, and Europe stands out as the region of stagnation.
The effects of the EU’s “Super-Plough”
According to the The Furrow article, the ‘new’ plough combines the characteristics of an old plough, turning the soil 25 cm deep, with a subsoil digging up the soil to 55 cm, with the aim of stirring up even more soil. The oxidation of soil organic matter can only be expected to be catalyzed throughout the profile. The implement also requires increased tractive power (and fossil fuel emissions), and the heavy equipment results in compaction for which the manufacturer even recommends equipping tractors with tracks. Large investments and high operating costs, not what a farmer is looking for.
Nevertheless, this extraordinary plough still has arguments for German farmers and other Europeans who are used to following the instructions of the “good practices” of the Common Agricultural Policy (CAP) in exchange for the subsidies that make up their income. If the greening of CAP proceeds as some pace, as expected, some farmers reluctant to change from historic practices may find they have painted themselves into a corner.
Farmer unions may use this project to present themselves to the arena of public opinion with a green image on a narrow component of the climate issue. The project may also enable the tillage needed for Organic certification to obtain a shade of a green image. Proponents should hope the public or policy makers do not ask for the whole life-cycle or footprint of the practice in terms of carbon or ecosystem services. The DG Environment should be transparent and accountable for public funds supporting universities and institutes for all projects that profess green outcomes.
The article further claims a yield increase of the crop may be realized due to an increased loosening of the soil at depth. This is an example of the known relationship of tillage cutting and mixed organic material to enhance mineralization of nutrients as the organic matter speeds up decomposition (eg. a single ploughing of an old meadow very quickly releases more than 400 kg of Nitrogen / hectare (Source INRAE) in the form of plant-available nitrate). The nutrients are available for the crop that follows, perhaps even before the crop needs it, and since nitrate is very soluble it can easily move downward or overland, polluting aquifers, rivers and lakes.
A question of coherence of EU agricultural policies
What is the coherence of the EU, at the same time advocating “Soil Health” through its new eponymous Directive, and at the same time using public funds for land degrading tools that would degrade soil health and the larger environment?
How can EU policy nudge equipment manufacturers caught in old paradigms of equipment and agriculture practice become innovative and address the challenges of the future with new technology and innovative tools for sustainable practices that increase soil health and ecosystem services?
Rather than varying degrees of polemical exchanges from university studies or press articles between stakeholders and advocates of the various interests and disciplines, would not a tour of the fields allow farmers, industry, scientists, bureaucrats to see first-hand the results of the methods described, to share a common repository of knowledge, and to reach a consensus on a coherent Agricultural Policy?
2. cf. the work of D. Reicosky, R. Lal, INRAE, CIRAD, IRD and many research centres from all over the world.
Non-contractual illustration made with an AI from a prompt
Image by jacqueline macou from Pixabay
L’Agriculture de Conservation des Sols sème ses graines à la FAO
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