Science Year of the Bioeconomy
Keeping the nitrogen in the soil
➊ ➋If grains, potatoes and vegetables are to thrive and provide a rich harvest, they need nitrogen in the first place. This is why farmers apply nitrogen fertilisers to the fields – the required amount can be adjusted specifically by measuring the soil and observing the plants.
➌After harvesting, the leaves of the plants remain on the fields, for example in the case of rapeseed and potatoes. The leaves rot over time and release the nitrogen stored in them back into the soil as autumn progresses. There, bacteria convert it into nitrate.
➍Rain washes the nitrate into the ground water and indeed to a considerable extent: in this way, up to 100 kilograms of nitrogen per hectare can find their way into the drinking water per year.
Bacteria store the nutrient
How can drinking water be protected from nitrate, and how can the nitrogen be saved over autumn and winter into spring and summer so that it is then available again for the growing plants?
3a4a Together with partners, IBG-3 researchers have found possible solutions in the Inplamint project. “After the harvest, we put biomaterials such as wheat straw or sawdust on the fields,” says project leader Prof. Nicolas Brüggemann from IBG-3.
5a The biomaterials release carbon, which serves as food for bacteria and fungi. Due to the good feed supply, the bacteria and fungi – in short, microorganisms – proliferate. The trick: besides carbon, they also absorb nitrogen from the soil.
6a What sounds simple has a great effect: with four to five tons of wheat straw per hectare, between 40 and 70 kilograms of nitrogen can be stored in the microbial biomass per hectare. Over the months, the carbon release of the wheat straw declines, the bacteria die, the nitrogen is released and is available to the plants again.
Janine van Ackeren
Illustrations: Forschungszentrum Jülich/Barbara Schunk