Nitrogen balances of ecosystems, landscapes, and watersheds

Abstract

The dynamics of different quantities of nitrogen cycling on the scale of a typical agricultural ecosystem in North Germany (Schleswig-Holstein) were investigated. With special reference to microbial transformations, a process-orientated model was applied to simulate the inorganic (Nmin), the dissolved nitrogen content of the soil and leaching. The use of deduced and statistical data permits scaling nitrogen cycling up from a specific point up to a complete catchment area, in this case the watershed of Lake Belau because of the spatial reference of the model. Therefore, nitrogen cycling of a forest ecosystem belonging to the area was also considered. While measurements generally represent single points at selected times, simulations permit a continuous and extensive description of nitrogen cycling on any scale. Thus, simulation makes it easier to forecast the effects of agricultural management and supports the development of basic principles in order to plan a more efficient use of nitrogen. This use of nitrogen was observed to be very poor when the exports in agricultural products were related to the total level of imports in the area.