Aim of Soil³ is to provide scientific knowledge for practitioners. The coupling of strategies of research and production, services, arable management strategies, and providing of software tools are main bricks. Indicator systems of the acquisition of water and nutrients from the subsoil are applicable for monitoring success. Different technical means and manipulation options of the subsoil are tools for economic utilization. Identifying of genotypes could be coupled with commercial plant breeding industry.
Project results from phase 1 and 2
Subsoil is more heterogeneous in its physico-chemical properties than topsoil. Root access to subsoil resources is site-specific but can be enhanced by topsoil management, particularly N fertilization and liming, as well as by biopores and loosening, with greatest yield effects under seasonal drought. For specific subsoil management we developed a tool for strip-wise compost injection into subsoil. This stabilizes or even increases crop yields by 20%, depending on weather conditions and topsoil management. Subsoil management is most promising and sustainable in well-drained sandy soils, regions with layers restricting root growth, and regions facing extreme climatic events. Implementation of subsoil management might be best feasible under clear ownership conditions combined with organic farming.
Positive effects of stripwise subsoil melioration with compost with respect to crop yields and soil quality, e.g. microbial community, nutrient status and carbon storage, last for min. 4 years. Moreover, no enhanced nitrate leaching was found. With costs of 800 €/ha and yield increases of 23-55%, the technique becomes profitable after 4 years. Subsoil melioration could give access to 45-60% of nutrient and water resources in German farmland, with most promising success in Northeastern Germany characterized by summer drought. Acceptance of subsoil melioration by farmers varies among regions and is generally higher for biological measures (biopore formation via precrops) than for more invasive mechanical treatments.
Expected results phase 3
We aim at i) determining longevity of yield gains and soil quality (carbon, water and nutrient storage) via both technical and biological subsoil melioration also in lower-value soils, ii) evaluating water and nutrient use efficiencies against conventional soil management techniques, iii) providing a systematic tool for selection of organic amendments, iv) monitoring the performance of various crops under subsoil melioration and v) regionalization of costs, risks and benefits. This will enable us to provide implementation advice and outreach materials for the public, farmers, industry and science.