BayCEER Workshop 2023

N-Fertilization of Grasslands: Estimate on a field level by an Agent-based Model

Agricultural landscapes provide multiple important ecosystem services such as fodder production, erosion regulation, carbon storage or recreation for people. These services are under risk due to intensification of land-use and climate change. Consequently, a sustainable management system including the distribution of fertilizer is very important as nitrate leakage can cause drinking water contamination. Therefore, nitrogen content is a fundamental input factor for agricultural and biophysical models. So far, there is not enough data to pre-estimate the N-deposition on a regional scale. We developed an Agent-based model in NetLogo to simulate the load of nitrogen deposition and its changes with new regulations based on land use and livestock data on a farm level for the catchment of the Ammer lake. The agents are represented by farmers. The model considers factors like cost benefit expectancies, subjective norms and environmental constrains (Theory of Planned Behaviour). For the Ammer region, we found, that the N-demand was smaller than the maximum amount of organic fertilizer (170 kgN/ha) allowed to apply. However, this region is mostly grassland dominated. To extrapolate the results on other regions of Bavaria, an application of the model on the Roter Main/Weißer Main catchment area (mixed land use of grass- and cropland) is necessary. The ABM will need certain modifications to estimate valuable results for croplands as well as grasslands. This model approach helps to observe and model effects of different land use management systems and their resilience towards provisioning ecosystem services including the farmers individual perspective. It offers the opportunity to develop schemes for a sustainable agricultural system.