Nitrogen balance of arable soils
Investigations on the nitrogen balance in arable soils include the processes of N-mineralisation and mineral-N-displacement prevailing during the winter half-year and the N-dynamics during the vegetation period (here mainly ammonium fixation and defixation; dynamics of microbial biomass). A part of these investigations is carried out using labelled nitrogen (15 N).
Long-term C- and N-dynamics of different ecosystems
For quite some time, studies have been carried out on long-term C- and N-dynamics in agricultural systems (e.g. C- and N-accumulation in soil organic matter after crumb deepening, N-release after grassland ploughing, C- and N-dynamics after compost application and in different tillage systems, stabilisation of soil organic matter). The activities in forest ecosystems focus on the long-term source and sink functions of forest soils, the effects of increased N-inputs on humus morphology and quality, and mineral N-development under anthropogenic influence.
Nutrient balances in German agriculture
Long-term balances (1950 to the present day) for nitrogen, phosphorus and potassium in agriculture are drawn up both at regional (countries) and national level. The nutrient surpluses calculated from these balances are evaluated from an ecological and economic point of view.
International cooperation
There is intensive cooperation on questions of the carbon and nutrient balance of soils with research groups in Great Britain, Italy, Spain, Russia, Rwanda and India, among others. Benbi (Indian cooperation partner) has resulted in the textbooks "Handbook of Processes and Modeling in the Soil-Plant System" (Haworth Press, New York) [http://www.soil.tu-bs.de/etc/handbook.pdf] and "Carbon and Nitrogen in the Terrestrial Environment" (http://www.springer.com/978-1-4020-8432-4). In addition, the working group has been conducting studies on the N balance in China for many years.