Degradation of Complex Carbon Sources in Organic Fertilizers Facilitates Nitrogen Fixation

Biological nitrogen fixation is crucial for agriculture
and improving
fertilizer efficiency, but organic fertilizers in enhancing this process
remain debated. Here, we investigate the impact of organic fertilizers
on biological nitrogen fixation through experiments and propose a
new model where bacterial interactions with complex carbon sources
enhance nitrogen fixation. Field experiments showed that adding organic
fertilizers increased the nitrogenase activity by 57.85%. Subculture
experiments revealed that organic fertilizer addition enriched genes
corresponding to complex carbon and energy metabolism, as well as nifJ involved in electron transfer for nitrogenase. It also
enhanced bacterial interactions and enhanced connectors associated
with complex carbon degradation. Validation experiments demonstrated
that combinations increased nitrogenase activity by 2.98 times compared
to the single. Our findings suggest that organic fertilizers promoted
nitrogen fixation by enhancing microbial cooperation, improved the
degradation of complex carbon sources, and thereby provided utilizable
carbon sources, energy, and electrons to N-fixers, thus increasing
nitrogenase activity and nitrogen fixation.