Optimising Cropping Techniques for Nutrient and Environmental Management in Organic Agriculture.

Recent research results and methodological progress have increased our insights and understanding of root growth and soil-root interactions. Depth and architecture of root systems play a prominent role in crop productivity under conditions of low water and nutrient availability. The subsoil provides supply with finite resources such as phosphorus that have to be stretched through moderate use thereby delaying exhaustion. For instance between 25 and 70 % of total soil P may be allocated in subsoil layers. As a function of time taproot systems especially those of perennial legumes can unlock soil nutrients from the solid phase and increase the density of vertical biopores in the subsoil thus making subsoil layers accessible for succeeding crops.Biopore density is further enhanced by increased abundance and activity of anecic earthworms resulting from soil rest and provided feed. Nutrient rich drilospheres can further provide a favorable environment for roots and nutrient uptake of following crops. Future efficient nutrient management and crop rotation design in Organic Agriculture should entail these strategies of soil fertility building and biopore services in subsoil layers site specifically. Elements of these concepts may be used also in mainstream agriculture headlands in order to establish a web of biodiversity while avoiding constraints for agricultural production. Beyond this, suggestions of future opportunistic cropping and opportunistic tillage entail intensive mouldboard ploughing as well as occasional direct seeding of grain legumes. The latter was shown a suitable, labor and fuel saving cropping technique in Organic Agriculture. Both, introducing perennials into crop rotations and occasional direct seeding are easier realized under mixed farm systems providing per se higher planned as well as associated diversity and enhanced ecosystem services.