Bio-based fertilizers can reach agronomic performance of synthetic fertilizer in broccoli production under two climate scenarios

Bio-based fertilizers (BBFs) are part of the circular economy model for Europe to achieve climate neutrality by 2050, decoupling economic growth from resource exhaustion and maintain agronomic production within planetary boundaries. Here, an Ecotron experiment evaluated agronomic performance and greenhouse gas (GHG) emissions (N2O, CO2) of four BBFs compared to a synthetic fertilizer (SYN) in broccoli production under a historic reference and a future RCP8.5 climate scenario for Belgium. Crop production parameters such as element use efficiencies and yield were similar or lower for plants receiving BBFs compared to SYN in the reference climate, but similar or higher for BBFs compared to SYN in the future climate. Mechanistically, cropping systems with BBFs benefited from enhanced soil microbial activity compared to SYN in both climates (measured as hydrolysis of fluorescein diacetate), but concurrently also had higher GHG emissions. The risk of nitrate leaching was indifferent amongst fertilizers but globally increased in the future climate with more intense dry-rain shifts. While these results support BBFs as agronomic alternatives to SYN, further research is needed to address climate-induced yield penalties which were observed for all fertilizers (BBFs & SYN) in the future climate.