Linkages between soil nutrient turnover and above‐ground crop nutrient metabolism: The role of soil microbes

With global agricultural practices increasingly focused on sustainability and efficiency, deciphering the complex relationship between soil nutrient turnover and crop nutrient uptake is critical for advancing crop productivity and environmental resilience. This study focuses on the nitrogen transformation process following dazomet soil fumigation and examines how soil microorganisms influence both soil nitrogen cycling and above-ground crop nitrogen metabolism. Fumigation led to significant changes, with ammonium nitrogen increasing by 18.89%-94.82% and nitrate nitrogen decreasing by 30.20%-90.21% in tobacco roots, stems, and leaves. Fumigation also caused a notable shift in the soil microbial community, inhibiting ammonium-oxidizing microorganisms while stimulating denitrifying microbes. These changes not only disrupted the nitrogen balance-reducing soil nitrification by 72.91%-86.51% and increasing denitrification by 197%-324% but also had a cascading effect on above-ground crop nitrogen metabolism. By altering the composition of microbial communities, the process directly influenced soil nutrient turnover, subsequently impacting nutrient availability and distribution in crop. The disruption in nitrogen balance further led to changes in the expression of key nitrogen metabolism enzymes and transporter genes. Specifically, genes related to nitrate and ammonium transporters, as well as amino acid and nitrogen metabolism enzymes, were upregulated. Structural equation modeling confirmed that the shifts in the microbial community were central to driving changes in both soil nutrient turnover and nitrogen distribution in the crop. These findings underscore the critical role of soil microbial communities as a link between soil nutrient cycling and above-ground nutrient metabolism, highlighting their importance in regulating plant nutrient absorption and utilization. This suggests that optimizing microbial management strategies could lead to significant improvements in crop nutrient efficiency.