Interplay between Biological Nitrification Inhibitors, Nitrogen Cycling, and Agronomic Nitrogen Use Efficiency

Nitrogen is an essential element in terrestrial ecosystems. However, plants cannot directly assimilate atmospheric nitrogen, and therefore nitrogen is often a limiting nutrient for plant growth. Nitrogen cycling processes in soil (i.e., nitrogen fixation, nitrification, and denitrification) are catalyzed by microorganisms and are heavily influenced by plant-microbe interactions. However, the biochemical, physiological, and genetic mechanisms behind this metabolic interplay and the crosstalk between plants and microorganisms remain poorly understood. The process of nitrification within the terrestrial nitrogen cycle is of particular interest as it is responsible for nitrogen loss from fertilized soils, which leads to the eutrophication of aquatic ecosystems and causes devastating ecological damage worldwide. This project focuses on the modulation of soil nitrification by inhibitory compounds naturally produced by plants - biological nitrification inhibitors (BNIs). Currently, the influence of BNIs on nitrogen cycling microorganisms in soil and the soil microbial community is largely unknown. We propose to i) identify novel BNIs from crop plants, ii) characterize the nitrification inhibition potential of BNIs, iii) determine the impact of BNIs on nitrogen cycling and general microbial activity in soil, and iv) investigate the effect of BNIs on soil nitrogen retention and nitrogen transfer from soil to crops. We hypothesize that novel BNIs identified in this study will function as effective nitrification inhibitors while minimally impacting other soil microbial processes, improving soil nitrogen retention, and increasing crop nitrogen use efficiency. We will test these hypotheses using state-of-the-art high-throughput technologies (i.e., metabolomic profiling, metagenomic microbial community analyses, single-cell chemical imaging, and stable isotope tracing) in experimental laboratory-scale plant-soil systems. These techniques enable us to investigate the effect of BNIs on plant-microbe and microbe-microbe interactions, elucidate underlying physiological mechanisms of nitrification inhibition, and identify BNIs suitable for agricultural application.