Current agricultural practices are a major cause of environmental degradation. Consequently, the development of sustainable agricultural practices is one of the greatest challenges for the agricultural sector. This especially applies to tropical climates where agroecosystem functions are threatened by human-induced climate change. Intensive fertilization in conventional agricultural practices fosters excess soil nitrogen, which is related to a range of environmental issues like greenhouse gas emissions, loss of biodiversity or water pollution. Organic farming systems aim to close nutrient cycles and are proposed as a viable option to reduce the impact of agriculture on ecosystem health. Although soil microbial communities play a vital role for soil fertility and agricultural production, we still have a limited understanding of their functional role in organic and conventional farming systems. The project aims to conduct a systematic assessment of the functional potential of soils in nitrogen cycling under organic and conventional farming systems across climatic conditions. To this aim, stable isotope tracing, quantification of functional marker genes and amplicon sequencing technologies will be used to characterize soils from organic and conventional farming systems. System comparison trials in Kenya, India and Bolivia will serve as a research platform for the tropical climates. For the temperate climate, the DOK system comparison trial in Therwil (Switzerland) will be used to characterize not only shifts in diversity but also in the metabolic potential of the soil microbiome during the vegetation phase. In this field trial, shotgun metagenomics and metatranscriptomics will be employed to identify key species for agricultural production in organic and conventional farming systems. By linking results of molecular biological methods to soil functions and plant nitrogen uptake, we will obtain new insights into the drivers of agricultural production. In turn, the outcomes will assist the future development of environmental and climate-smart agricultural practices in the temperate and tropical climate.
