Sustainable agriculture

Depot fertilization releases significantly less greenhouse gases

Although nitrogen fertilizers help farmers to achieve high yields, these good harvests come at a cost. Nitrogen fertilization produces ammonia (NH3), which is harmful to both health and the environment, as well as the greenhouse gas nitrous oxide (N₂O). On top of that, increasing energy and raw material prices are driving up the cost of fertilizers. This means that in the future fertilizers should be applied specifically near the roots instead of being poured out indiscriminately as they are currently.

Gas concentration measurements enable efficient use of fertilizer

Specialist companies like RAUCH Landmaschinenfabrik GmbH, our partner in the ESKILA project, are working on techniques for a fertilization method known as depot fertilization, where long-term nitrogen fertilizers are injected into deeper layers of soil selectively or via trenches in the soil. This method releases significantly fewer greenhouse gas emissions than the extensive spreading of fertilizer. A mobile photoacoustic spectrometer that we are developing as part of the ESKILA project is particularly suitable for measuring the concentration of nitrous oxide released during depot fertilization and therefore helps fertilizer to be applied efficiently. A series of field tests were performed to compare various fertilization strategies on different parcels of land being used to grow typical varieties of crop. Data will be collected and evaluated at up to 60 measuring sites per fertilization period until the end of the project in fall 2025.

Mobile low-energy system – for use directly in the field

The laser-based gas measurement system measures the N₂O concentration using photoacoustic spectroscopy in the ppb range directly in the field without the need for any samples to be prepared and within a matter of seconds. Building on a demonstrator designed during Fraunhofer’s »Cognitive Agriculture« lighthouse project, the team developed a cost-effective and robust measurement system, which – thanks to its novel interband cascade laser – has very low power requirements so it can be used as a mobile device when operated in battery mode. Measuring chambers have been placed in specific locations in the test areas and the mobile gas measurement system is gathering data from each of these sites multiple times in accordance with a predetermined plan. The increase in the concentration of N₂O over a few minutes is recorded each time measurements are taken and the gas flow at the site is then calculated over the course of the measurement.