Model-based life cycle assessment of nitrogen fertilization in a cauliflower-leek rotation system

Current horticultural practices in Belgium use large amounts of inorganic fertilizers to attain high yields and quality. This practice results in an exceedance of the legally imposed residual soil nitrate threshold value of 90 kg N-NO3 ha-1 at the end of the growing season. An experiment was been set up to monitor and evaluate the influence of two nitrogen fertilizer application rates (high-low) and two strategies (broadcast-fertigation) on the growth, yield and quality of a cauliflower-leek crop rotation. Their respective impacts on the environment were investigated in a life cycle assessment considering fertilizer production and application, plus the auxiliary equipment and energy use. The nitrogen processes in soil inducing field emissions were estimated either by commonly used empirical models or by a mechanistic approach. A soil transport model adapted from WAVE, focusing on mineralization and nitrate leaching, was linked to a generic crop model, including transpiration and water-demand, N-demand and -uptake. A Life Cycle Assessment focused for each fertilization treatment on the differences in input loads and their corresponding environmental impacts in terms of different categories: global warming, cumulative energy demand, human toxicity, acidification and eutrophication. A higher nitrogen application rate resulted in an overall higher impact in all categories. Fertilizer production has a high impact on human toxicity, global warming potential, acidification and cumulative energy demand. While fertilizer application increases eutrophication, acidification and global warming potential, fertigation dramatically increases the cumulative energy impact. With the model based approach environmental impact over different cropping years can be evaluated and compared.status: publishe