Aggregation of activity data on crop management can induce large uncertainties in estimates of regional nitrogen budgets

This study quantitatively inter-compares three approaches to drive the process-based model LandscapeDNDC on a regional scale using data from the Danish Agricultural Watershed Monitoring Program (LOOP). The aim is to assess how assumptions and simplifications about farm management activities at a regional scale affect the simulation of yields and the nitrogen budget (NB) of cropping systems. Findings reveal that the detailed field-level management data approach (A) best simulates yield (r² = 0.93), while aggregated approaches (B and C) show lower but significant correlations. Significant differences arise in NB simulations, especially concerning N losses. Approaches B and C overestimate gaseous N fluxes and nitrate leaching compared to approach A, highlighting the importance of careful management representation in large-scale NB simulations and environmental impact assessments.

Jaber Rahimi, Edwin Haas, Clemens Scheer, Diego Grados, Diego Abalos, Meshach Ojo Aderele, Gitte Blicher-Mathiesen, Klaus Butterbach-Bahl