The biodynamic D (Demeter) system builds up substantial amounts of humus over the entire duration of the experiment. The bioorganic O (Bio Suisse) system and, to a lesser extent, the conventional K system also show a slight increase in humus. The M system loses humus. The quantity of microorganisms and their activity in the soil, as well as their ability to mobilise nutrients, are on average 44% higher in the organic systems than in the conventional systems. In summary, the greenhouse gas emissions of the biodynamic areas D were 63%lower and the bioorganic areas O 44% lower than those of the conventional system K.
If the change in humus is taken into account, the O system emits 45% fewer CO2 equivalents, and the D system as much as 74% fewer.
Ecological engineers make the difference
Dr Andreas Fliessbach, Dr Paul Mäder and Dr Hans-Martin Krause (all FiBL)
The loss of soil fertility and biodiversity, as well as the effects of climate change, are the greatest challenges facing agriculture.
Humus formation and reduced nitrogen fertilisation against climate change
By building up humus and thus storing CO2 in organic matter (humus), organic farming helps to alleviate the current global problems of soil fertility loss and climate change. Greenhouse gases such as CO2, methane and nitrous oxide, which originate in the soil, have a very significant impact on the climate. Reducing their use is therefore a central concern of sustainable agriculture.
In the DOK trial, soil fertility was measured over more than 40 years, and it was found that the most sensitive indicators of soil fertility are soil organisms and what they do.
In addition, greenhouse gases were measured at more than 80 points in time in the DOC trial across a section of crop rotation. The measurements covered a grass clover-maize-green manure crop rotation sequence for 571 days and were usually taken once a week, with additional measurements after tilling and fertilisation.
The biodynamic soils with high structural stability
Soil fertility and soil quality are often used synonymously, but soil fertility has the goal of producing fruit – so it has an agricultural context.
It can be recognised by undisturbed plant growth, site-typical soil structure, active biological communities and undisturbed decomposition of plant residues. It takes years of observation by farmers or much more complicated analysis to assess soil fertility well.
While the pH value remained constant in the bioorganic soils O (Bio Suisse) and even increased in the biodynamic system D (Demeter), massive liming was necessary after 21 years of conventional cultivation. Without liming, plant growth and soil fertility would have been reduced. The loess soil at the research site, with its high silt content, is very fertile but tends to silt up and, on slopes, to erode. The organically farmed soils, and in particular the biodynamic D soil, showed a lower tendency to silting and better structural stability than those of the conventional systems as a result of a higher humus content and higher biological activity.
The importance of animal husbandry for soil fertility
In all systems that were supplied with manure and slurry, the humus content and stocks could be maintained or slightly increased. However, with the biodynamic manure compost, the D system achieved statistically verifiably higher humus levels than all the other systems. In the conventional system M with exclusively mineral fertilisation, the soils lost humus. This shows how important animal husbandry and the circular concept of organic farming are.
An important indicator of fertile soil is the quantity and activity of soil organisms. The quantity of microorganisms and their activity indicates the soil's ability to transform substances. It was 83 percent higher in the organic systems than in the conventional ones.
Microorganisms are crucial for the soil to function properly. FiBL studies have shown that microorganisms are important for numerous soil functions: nutrient cycling, erosion control, climate regulation and the regulation of diseases and pests. The biodynamic system is also better than the other systems at mobilising nutrients such as phosphorus from the soil's organic reserves, which is indicated by what is known as phosphatase activity.
A higher diversity of microflora and soil animals in organic soils also indicates higher soil fertility. Recent studies in the DOK trial show that the application of manure and slurry has the greatest impact on soil organisms compared to the application of mineral fertilisers alone. But the form of the farmyard manure (manure compost versus rotted manure or stacked manure) and the pesticides also influence the soil organisms.
CO2 sequestration and greenhouse gas emissions
Scientists attribute current climate change to the accumulation of greenhouse gases (GHG) in the atmosphere, which cause solar radiation to pass through the atmosphere from the outside, but inhibit the reflection of heat from the earth into space. The three most important GHGs – also in terms of agriculture – are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).
Climate protection means reducing the concentration of GHGs in the atmosphere – in other words, reducing emissions and/or increasing the sequestration of GHGs, especially CO2. The political goal of the COP (United Nations Framework Convention on Climate Change) to limit the global temperature increase to 1.5°C is rooted here. Climate change adaptation involves measures to mitigate the consequences of climate change. Adaptation strategies in agriculture help to reduce the risks associated with the expected extreme weather events (heat, flooding, drought, erosion).
Root penetration stabilises the soil
Many of the proposed measures are already practised in organic farming. More humus in the soil can help to reduce soil loss through erosion and to store more water in the soil. Diversifying crops can reduce economic risks. Cultivation systems with permanent ground cover make full use of the photosynthetic capacity of plants to bind CO2. Intensive root penetration stabilises the soil. Biodynamic agriculture D (Demeter) is the only DOK system that stores substantial amounts of organic carbon in the humus with normal fertilisation, probably by stabilising the organic components when composting manure with biodynamic preparations.
Furthermore, the lowest nitrous oxide emissions were measured here, while the high nitrogen fertilisation in the conventional systems K and M lead to increased GHG emission rates. CO2 sequestration through humus formation and greenhouse gas reduction in the biodynamic system D results in a 74 percent lower climate impact compared to the conventional system K with manure. The climate impact of the two organic systems together is 55 percent lower than that of the two conventional systems.
It is also noteworthy that when the plant is cultivated organically, it transports more carbon compounds from photosynthesis into the underground part, i.e. into the roots and root exudates, than into the above-ground part. These results are central to model calculations of the climate impact of agricultural systems.
