Biological soil quality as a factor of efficient resource utilization in organic farming systems

Summary

In 1978 the DOK long-term field experiment was installed at Therwil close to Basel comparing the farming systems „bio-Dynamic“, „bio-Organic“ and „(K)conventional“. In the first years of the trial, crop yield and feasibility of organic farming were investigated. Soils were analysed with respect to long-term effects on fertility and were evaluated in the view of farming effects on the environment. Today the interrelation of diversity and efficiency and the quality of organic products is the research focus. Long-term trials like the DOK-trial offer unique opportunities for this kind of research.
The DOK-trial compares the three systems mentioned above on the basis of the same intensity of organic fertilization (i.e. the same number of animals per area), the same crop rotation and the same soil tillage. Fertilization and plant protection are different and done according to the farming system. A minerally fertilized conventional treatment is mimicking stockless farming and unfertilized plots serve as controls.
Crop yields of the organic systems averaged over 21 experimental years at 80% of the conventional ones. The fertilizer input, however, was 34 – 51% lower, indicating an efficient production. The organic farming systems used 20 – 56% less energy to produce a crop unit and per land area this difference was 36 – 53%.
Maintenance of soil fertility is important for a sustainable land use. In DOK field plots the organically treated soils were biologically more active than conventional, whereas chemical and physical soil parameters differed less significantly. Soil organic matter after 21 years shows substantially higher values in farming systems with manure fertilization and especially in biodynamic field plots fertilized with composted farmyard manure. Organic farming systems are suggested to utilize non-renewable resources more efficiently due to a higher inherent soil fertility.