On average across all crops, the two organic systems achieved 85% of the yields of the conventional systems, with about half the energy and nutrients, and only a very small amount of biocompatible pesticides. On average across the crops, there were no significant differences in yield between biodynamic (D) and bioorganic (O) crops.
In comparison to the O system, the D wheat yields were around 20% higher in the last two rotations.
Conversely, the O system achieved around 15% higher yields than system D in potatoes thanks to the permitted use of copper against late blight.
‘Maximum yields at any price’ versus ‘Less is more’
Text: Dr Paul Mäder, Dr Andreas Fliessbach, Dr Hans-Martin Krause, all FiBL
Over the last four decades, lower yields have been measured in organic systems compared to conventional ones in the DOK trial, in line with global research results. These were particularly pronounced in non-legumes such as potatoes (34%) and wheat (20%) and moderate in maize (12%). The yield gap for grass clover was 10 percent, while there was no difference in yield between the two systems for soya.
The differences in yield levels can be attributed primarily to mineral nitrogen fertilisation, such as ammonium nitrate. In particular, a strong correlation between nitrogen input and yield was observed for wheat and potatoes. A limitation of yield by other nutrients such as potassium, phosphorus or sulphur has not been observed so far. Crop protection has had a significant influence on yield stability.
Increased yield also in organic systems, but the gap remains
It is particularly noteworthy that it was possible to increase the yield level of the organically grown wheat in the last two crop rotation periods. This may well be attributable to new breeding successes. With the Wiwa variety of the Getreidezüchtung Peter Kunz gzpk cereal breeding programme, a variety optimised for organic systems has been cultivated since the fifth crop rotation period.
The higher yields in conventional systems are mainly achieved through the use of external inputs such as pesticides and fertilisers – with negative environmental impacts. Calculations of the nitrogen balance show unavoidable nitrogen losses due to nitrate leaching and ammonia degasification, for example, of around 45kg of nitrogen per hectare per year in the conventional systems.
Society pays the environmental costs
In organic systems, these nitrogen losses are significantly lower, at around 20 to 25kg nitrogen per hectare per year. This comparison shows that maximum yields come at an environmental cost. Ultimately, society bears the environmental costs arising from the high usage of fertilisers, pesticides and energy in conventional systems. The consequences of conventional farming are a loss of biodiversity and soil fertility, increased greenhouse gas formation and contamination of food and drinking water.
