Nitrogen (N) losses from agroecosystems pose a major challenge for sustainable agriculture and environmental protection. Nitrification, the conversion of ammonium (NH₄⁺) to nitrate (NO₃⁻), is a critical step in the N cycle where N losses can occur. While synthetic nitrification inhibitors are used in conventional farming, organic systems are looking for alternatives, such as plants with biological nitrification inhibition (BNI) capacity. BNI refers to a plant's ability to inhibit nitrification by suppressing nitrifying bacteria, causing a delay in nitrification and therefore can potentially reducing N losses. Plantago lanceolata has shown potential as a BNI-active plant.
In central European organic farming, temporary grass-clover leys play an important role in crop rotations, providing N through legume symbiosis, enhancing soil fertility, and improving soil structure. These leys are usually terminated after 1–2 years to plant succeeding crops. However, during and after ley termination, large amounts of mineralized N are vulnerable to losses via NO₃⁻ leaching and N₂O emissions. To address these issues, incorporating P. lanceolata into ley mixtures could mitigate N losses.
This hypothesis will be tested using large pot experiments in a climate chamber. Different proportions of Plantago lanceolata will be grown together with grass and clover. The aim is to access N cycling dynamics in order to evaluate the potential of P. lanceolata to reduce N losses after ley termination. The study is designed with three phases.
During the Growth Phase (G1: Summer 2025 – Summer 2026), P. lanceolata is cultivated alongside grass and clover in microcosms to evaluate its influence on N cycling dynamics. Key measurements include biomass production, N uptake, N fixation by clover, and soil mineral N concentrations. In the Termination Phase (G2: Autumn 2026), following the final biomass harvest, ley termination is simulated in the same microcosms to assess N losses during this critical transition period. Measurements include NO₃⁻ leaching, gas emissions (N₂O, CH₄, CO₂), and soil mineral N, focusing on the potential of P. lanceolata to mitigate N losses after termination. Finally, in the Succeeding Crop Phase (G3: Autumn 2026 – Spring 2027), a succeeding crop is grown in the microcosms previously used for ley mixtures to determine the residual effects of P. lanceolata on soil nitrogen availability and crop performance. Across all three phases, soil samples are consistently collected to evaluate the impact of P. lanceolata on soil microbial communities.
The master student will perform one part of the microcosm study including measurements, sampling, sample preparation for analysis and statistical analysis and visualization of the data. Basic lab skills and experience in data handling with R Studio are required.
The master thesis work is possible to start at various timepoints / project phases between autumn 2025 and spring 2027 with focus topics adjusted to project phases
