Excessive fertilizer use in agriculture leads to nutrient imbalances, which are the cause of 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. Motivation is the development of 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. 

This interdisciplinary project supports the knowledge-based evaluation of potentials to optimize plant-microbial interactions and to improve the nutrient-use efficiency in agricultural crop production. The evaluation and characterization of these interactions directly supports the development of new agricultural management strategies to reduce nutrient losses and environmental pollution.

The synthesized knowledge helps to maintain and improve the soil functions and services of agricultural cropping systems even at regional scale.

Results from phase 1

The first phase showed that agricultural management has a decisive influence on the composition and functionality of the soil microbiome.

Furthermore, it could be shown that C:N:P stoichiometry plays an important role for N-binding and N-turnover in soil, and thus could play an important role in plant-microbial competition for nutrients.

The field trial demonstrated that N surpluses after winter oilseed rape and faba bean can be effectively bound with wheat straw and sawdust with a high C:N ratio, but that this bound nitrogen is not completely available in the following year, but predominantly only in the year after.

The socio-economic analysis showed that a widespread use of wheat straw and sawdust to bind N surpluses in agriculture would compete with alternative utilisation paths, in particular bioenergetic use.

Expected results from phase 2

The focus of the second phase is on studies on the stoichiometric nutrient relationships between plants, soil and microorganisms. The following aspects will be investigated in more detail:

(1) Effect of timing of fertilizer application and of high C soil amendments on nutrient use efficiency;

(2) Analysis of functional/ effect traits of microorganisms in response to different treatments;

(3) Direct effects of crops on the activity of the soil microbiome;

(4) Plant legacy effects on the soil microbiome;

(5) Deepen our understanding of C:N:P stoichiometry effects, with a focus on N:P ratios;

(6) Nutrient re-release from soil amendments.