Excessive fertilizer use in agriculture leads to nutrient imbalances, which are the cause of detrimental nutrient losses leading to surface and groundwater pollution as well as increased greenhouse gas emissions. A sustainable agriculture has to find ways to minimize this nutrient inefficiency, while
maintaining or even increasing crop productivity and quality as fundamental criteria of a bio-based economy. This project is motivated by the central hypothesis that novel plant cultivation strategies directed towards “engineering” the complex nutrient cycling interactions between plants and soil
microorganisms, combined with improved timing of fertilizer and soil amendment applications, are the key to optimizing nutrient use efficiency of crop production.

The overall objective of this project is to (a) elucidate the key processes governing nutrient turnover and fluxes in the plant–soil-microbial system, (b) assess their importance for nutrient-efficient agricultural biomass production, (c) concurrently optimize the combined use and timing of the main
nutrients N, P and K, and (d) derive suitable management options for optimizing nutrient-use efficiency in agricultural biomass production for different soil conditions and different climate change scenarios.

The project work will be conducted in three different phases of three years each. In the first threeyear phase, the basic mechanisms of plant–soil-microorganism interactions as a function of crop rotation, soil type, fertilization and soil amendment regime as well as temperature and moisture will be investigated. Research will concentrate on: (1) characterization of the soil microbiome as a function of long-term nitrogen fertilization with different substrates (mineral, manure, crop residues) and of time since soil recultivation; (2) investigating the effect of different fertilization and soil amendment regimes,
varying in amount, timing and substrate stoichiometry, on nutrient dynamics in the plant–soil-microbial system; (3) developing novel management options on the basis of substrate-induced microbial N immobilization for buffering excess N after harvest; (4) assessment of environmental and socioeconomic effects and screening assessment of novel management options.