Biofertilizers can enhance nitrogen use efficiency of sugarcane

Fertilizers are costly inputs into crop systems. To compensate for inefficiencies and losses from soil, farmers apply on average double the amount of nitrogen (N) fertilizer acquired by crops. We explored if N efficiency improves with biofertilizers formulated with organic waste, mineral N or plant growth-promoting rhizobacteria (PGPR). We compared treatments receiving mineral N fertilizer or biofertilizers at industry-recommended (100%) or lower (60%) N rates at two commercial sugarcane farms. Biofertilizer at the 60% N-rate generated promising results at one farm with significantly higher biomass and sugar yield than the no-N control, which matched the 100% mineral N treatment. This yield difference was accompanied by a shift in microbial diversity and composition. Correlation analysis confirmed that shifts in microbial communities were strongly linked to soil mineral N levels, as well as crop productivity and yield. Microbial co-occurrence networks further revealed that biofertilizer, including treatments with an added PGPR, can enhance bacterial associations, especially in the context of complex fungal networks. Collectively, the results confirm that biofertilizers have quantifiable effects on soil microbial communities in a crop system setting, which underscores the opportunities for biofertilizers to promote N use efficiency and the circular N economy.