Field Assessment of Biochar Interactions With Chemical and Biological N Fertilization in Pointed White Cabbage

ABSTRACT The interaction of biochar with mineral fertilization has attracted attention as a strategy to reduce N losses and enhance nitrogen use efficiency. In this study, we investigated the coapplication of biochar with two optimized fertilization strategies based on split urea and a microbial inoculant (Azospirillum brasilense) in a commercial pointed white cabbage crop. Additionally, we evaluated a third optimized N fertilization alternative, a biochar‐based fertilizer (BBF) enriched in plant‐available N, which was developed from the same biochar. We assessed environmental impacts such as greenhouse gasses (GHG) and NH3 emissions, yield‐scaled N2O emissions, and global warming potential (GWP). Additionally, we evaluated agronomical outcomes such as crop yield, plant N, and chlorophyll concentration. Moreover, we examined the N‐fixing gene's total and relative abundance (nifH and nifH/16S). Biochar and BBF exhibited similar crop yield, GHG, and NH3 emissions compared to split applications of the synthetic fertilizer. The main difference was associated with the higher soil C sequestration in biochar and BBF treatments that reduced the associated GWP of these fertilization strategies. Finally, biochar favored the activity of the N‐fixing bacteria spread, compared to the sole application of bacteria and BBF demonstrated a promoting effect in the soil's total abundance of natural N‐fixing bacteria.