Use and cycling of reactive nitrogen (N) in agricultural ecosystems is on the one hand of pivotal importance to sustain productivity and thus, food security. On the other hand, the inefficient use of fertilizer nitrogen by plants results in detrimental effects on soil quality as well as in undesired reactive nitrogen losses along hydrological and gaseous pathways that compromise air, soil and water quality, including adjacent natural ecosystems.
On 19 and 20 April 2023, 30 scientists from eight BonaRes Module A projects, the BonaRes Centre and external guests from Norway and Sweden, among others, met in Garmisch-Partenkirchen to discuss current understanding, knowledge gaps, and ways towards better mitigation of detrimental impacts of nitrogen cycling in agricultural ecosystems. Central topics were i) biotic and abiotic drivers of nitrogen turnover and nitrogen losses in agricultural soils, ii) nitrogen management, iii) modelling of nitrogen fluxes and turnover as well as iv) possibilities to transfer the new findings to practice.
The presentations and the lively discussions clearly emphasized the need of a systems perspective that considers the interplay of physical, chemical and biological processes to adequately address nitrogen turnover and retention in agroecosystems. In addition, it became obvious, that more knowledge about plants and their particular uptake mechanisms for N are needed to improve nutrient use efficiency. In this, also stoichiometric considerations are needed taking ratios of different nutrients and carbon into account to predict biological processes and their kinetics. To support this development, field experiments are needed to measure all relevant N fluxes (including dinitrogen) also via isotope tracing techniques in order to compile full ecosystem N balances with well constrained N inputs, internal gross N turnover processes and N losses. This comprehensive information is of uppermost importance to better inform and constrain simulation models used for assessing the environmental footprint of agricultural production systems from site to farm to regional scales.
Finally, it was discussed which research results are relevant for practice and in which form they can be passed on to the users. Ideas for first fact sheets were generated, further products will follow.