| Summary: | Arable land covers approximately one fourth of the global land area, but only half of it can be used efficiently for cultivation to feed the growing population. Modern agriculture has developed highly productive food and biomass-producing systems based on industrial principles, which has lead to a considerable environmental burden. Organic agriculture has expanded as a movement towards more sustainable food production, which aims to maintain the key functions and ecosystems services of soils. At present, approximately 0.7% of global and 4% of European agricultural lands are managed organically (Willer and Youssefi, 2007). Soil organic matter (SOM) and its turnover play a pivotal role in the biogeochemical cycling of nutrients and in the response of terrestrial carbon to future climate scenarios. Its fate and dynamics are mainly governed and understood by its properties and physiology of the soil organisms (von Lützow and Kögel-Knabler, 2009). A key to understand and define a sustainable agricultural soil system is to quantify the impact of different land use on soil structure and biogeochemistry, with emphasis on nutrient turnover. The goal of our future research is to evaluate SOM pools in different soil aggregate sizes under different farming systems (organic vs. conventional) and link them to soil biodiversity. Soils were selected along cultivation age gradients under subarctic (Iceland, Andosols) and continental climate (Austria, Chernozems). The further outcome of this research is to identify quantifiable natural indicators for farm sustainability assessments. Gained data will also be linked to energy balance and food productivity in order to get more insights in benefits of different farming practices.
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