Agronomic performance, energy analysis, and carbon balance comparing different fertilization strategies in horticulture under Mediterranean conditions

Production capacity evaluation and environmental sustainability assessment allow defining both the most appropriate fertilization strategies and the agricultural systems management. The aims of this study were to investigate the following, in a cauliflower-lettuce rotation: (i) agricultural system agronomic performance, (ii) fertilization treatments environmental sustainability through the energy inputs/outputs analysis, and (iii) carbon footprint through the GHG emissions and carbon sequestration analyses. Three fertilization strategies were compared: (i) CM, compost from municipal solid waste; ii) MIN, mineral fertilizers; iii) MIX, the CM compost plus a mineral fertilizer. Cauliflower and lettuce responses to fertilization were influenced by climatic conditions from year to year, and among the fertilizer treatments, the CM demonstrated a better resilience to the extreme weather events. It also showed the highest renewable energy (44.3%), suggesting that the substitution of mineral fertilizers with organic ones may help to reduce the non-renewable energy depletion, thus promoting the sustainability in horticultural systems. The CM was the most efficient treatment, since the energy stocked as C in the soil (145,889 MJ ha−1) and the net energy and the energy efficiency for cauliflower and lettuce (113,106 MJ ha−1 and 3.1, respectively) were the highest. Our results suggest that the application of the tested sustainable practices makes the farm a “sink” for the atmospheric CO2.