In comparison to the conventional systems, the organic systems D (Demeter) and O (Bio Suisse) received – exclusively through natural fertilisation – on average over the rotations:
55% of total nitrogen
25% of soluble nitrogen (exclusively in the form of manure and slurry)
65% of the amount of potassium
73% of the amount of phosphorus
Averaged over the six crop rotation periods and all crops, the following quantities of pesticides were used compared to the two conventional systems:
In the biodynamic system D (Demeter):
3% of the total quantity of conventional systems (Bacillus thuringiensis ssp tenebrionis in potatoes)
In the bioorganic system O (Bio Suisse):
13% (Bacillus thuringiensis plus copper preparations to combat late blight in potatoes)
Calculations with newer standard values show that the organic systems require about 30% less energy per unit area than the conventional (German: konventionell) system K and 60% less than the mineral system M. The differences are smaller per unit of yield. They are mainly caused by the high energy consumption for synthetic fertilisers and pesticides in conventional systems.
A mirror of Swiss agriculture
Text: Dr Paul Mäder, Dr Andreas Fliessbach, Dr Hans-Martin Krause, all FiBL
The mixed-type enterprise
In Switzerland, mixed farming, combining arable and livestock farming, is still relatively widespread. This operational system enables a circular economy in terms of feed and nutrients. The animals eat clover and grass, known as roughage, and produce milk and meat. Their excrement is used as valuable fertiliser on the farm in the form of manure and slurry to fertilise arable land and grassland. This type of farming offers many advantages in terms of both soil fertility and the efficient use of nutrients such as nitrogen. The DOK trial therefore reflects a mixed type of farming, both in terms of the choice of crops and the use of the farm's own fertilisers.
Crop rotation as the cornerstone of sustainable agriculture
The sequence of crops is called the ‘crop rotation’. In arable farming, a balanced crop rotation is the key to sustainable agriculture, which must largely manage without pesticides and synthetic fertilisers. In the DOK trial, the spread of crops in the Leimental (Basel-Landschaft), where the field trial is located, is taken into account, and the crop rotation has been continuously optimised in terms of nutrient utilisation, diseases and pests, as well as weeds.
So far, the trial has spanned six seven-year crop rotation cycles. The current crop rotation in the DOK trial is silage maize – soya – winter wheat – potatoes – winter wheat and two years of grass clover. Maize and soya were added to the crop rotation in 2000 to reflect the increasing cultivation of these crops. Wheat, soya and potatoes are used for direct human nutrition, while grass clover and silage maize are used as animal feed. Grass clover mixtures and soya fix nitrogen from the air with the help of nodule bacteria, making mineral nitrogen fertilisation unnecessary in organic systems. The same varieties are grown in all systems – when selecting varieties, we make sure that they are suitable for organic and conventional farming systems. The climate at the test site is mild, with an average annual temperature of 11.2°C and 872mm of precipitation per year. From 1978 to 2010, the temperature has already increased by 1.5°C, and dry spells and heavy rainfall are occurring distinctly more frequently.
As mentioned above, the fertiliser basis for the main cultivation systems in the DOK trial is cattle manure and slurry. While manure in the biodynamic system D (Demeter) is composted under addition of medicinal plant preparations and exposure to air, the stable manure in the bioorganic system O (Bio Suisse) is only rotted. During composting, the manure is converted into an earthy, pleasant-smelling fertiliser, while the straw-like structure of rotted manure remains largely intact. In the conventional (German: konventionell) system (K), the manure is stacked tightly as a classic manure stack, preferably under airtight conditions. In addition, mineral fertilisers are used in the K-system in accordance with the official growing recommendations. In an additional conventional system, which mimics a livestock-free operation (M), only mineral fertiliser is applied.
Plant protection through variety selection and cultivation
As mentioned at the beginning, crop protection in the biodynamic system D is based on Demeter guidelines, in the bioorganic system O on Bio Suisse guidelines, and in the conventional system K on the regulations of the so-called Proof of Ecological Performance (PEP). In both organic farming systems, pests and diseases are primarily controlled by variety selection and cultivation techniques such as crop rotation and weeds, as well as mechanically with tractor-drawn hoeing equipment.
A special feature of conventional systems is that, in addition to pesticides, chemical growth regulators are also added to wheat to keep the stalks short and prevent them from falling over when nitrogen fertilisation is increased. In the biodynamic system D, we use the field preparations horn manure and horn silica in addition to the compost preparations mentioned. Horn manure is spread over all biodynamic plots in early spring and late autumn, and once or twice over the young crops. Horn silica is used two to three times in ripening plants.
Thirty to sixty percent less energy
The most important driver of plant growth is solar energy, which turns CO2 into sugar through the process of photosynthesis in green plants. But agriculture also consumes energy in the form of fuel and lubricants for tractors and other machinery. Moreover, there is so-called grey energy in the inputs such as fertilisers and pesticides, but also in the seed.
Until now, this energy has come almost exclusively from fossil sources, which ultimately come from plants and animals that have been transformed into oil, gas and coal over very long periods of time under pressure and anoxic conditions. In a comprehensive life cycle assessment, the total direct and indirect (grey) energy demand was calculated that would be consumed on a field with standard plot sizes and standard machinery.
Despite these huge savings in resources, the organic systems achieve 85 percent of the conventional yields on average across all crops and over the entire duration of the trial, compared to conventional systems. See also next page.
The figure on page 5 [next article] shows the use of pesticides, fertilisers and energy, as well as examples of the yields of wheat, soya and potatoes.
