Balancing fertilizer application and nitrate leaching in agricultural management : a multiobjective analysis

To cope with the sharp increase of the population that has characterized the last century, and in order to meet the ever increasing demand for food, agriculture was forced to an increasingly exploitation of natural resources. To enhance the productivity of the land, over the past decades farmers used an always growing amount of fertilizers of mineral type. Yet, this has generated envi- ronmental concerns, as nitrates are drained in the shallow aquifer. The phenomenon of percolation from agricultural soils is related to a concurrence of two causes: the large amount of nitrates that are found in the soil during the growing period and the nitrate residue, namely the percentage of nitrogen that, entered in excess in the soil to maximize the productivity, remains on the ground even after the harvest . To better understand the causes and the impacts of these two factors, this thesis aims to develop a model which combines the simulation of the nitrogen cycle in soil and of the crop growth, in order to provide farmers with the set of information necessary to decide the timing and the magnitude of fertilizer interventions. Due to the presence of multiple, con icting interests (e.g., increase crop productivity to maximize the farmers pro t, minimize expenses for fertilizers and minimize environ- mental impacts), the analysis is performed according to a multi-objective perspective to eventually aid the identi cation of one (or few) compromise alternative. The potential of the proposed methodology has been tested on a realistic case study derived from the Muzza - Bassa Lodigiana irrigation district (Italy). Numerical results show that it is possible to reduce the expenses for fertilization and the envi- ronmental impacts of fertilizers application by adopting the combined simulation of the soil nitrogen cycle and of the grop growth.