Multi-Analytical Approach Reveals Potential Microbial Indicators in Soil for Sugarcane Model Systems

Area of Science:

• Soil Science
• Microbiology
• Environmental Science

Background:

• Sugarcane cultivation generates significant waste, including vinasse and straw, which can be utilized as soil amendments.
• Understanding the impact of organic and inorganic amendments on soil microbial communities and greenhouse gas emissions is crucial for sustainable agriculture.
• Microbial biomass (MB) and specific bacterial taxonomic groups play vital roles in soil health and nutrient cycling.

Purpose of the Study:

• To investigate the effects of synthetic nitrogen (N), vinasse (V), and sugarcane straw on microbial biomass (MB) and bacterial taxonomic groups in sugarcane soils.
• To assess the influence of these amendments on soil chemical factors and greenhouse gas emissions (CO2-C and N2O-N).
• To identify bacterial groups that can serve as early-warning indicators of soil management practices in sugarcane cultivation.

Main Methods:

• Greenhouse mesocosm experiment with sugarcane-cultivated soils.
• Combinations of synthetic nitrogen, vinasse, and sugarcane straw blankets were applied.
• Monitoring of gas emissions (CO2-C, N2O-N), soil chemical factors, microbial biomass carbon (MB-C) and nitrogen (MB-N).
• Metagenomic sequencing (57 datasets) and 16S rRNA gene-targeted real-time PCR were used to analyze bacterial community composition.

Main Results:

• N and V amendments increased CO2-C and N2O-N emissions, elevated MB-N, and decreased MB-C in soils.
• Actinobacteria, Planctomycetes, Deltaproteobacteria, Alphaproteobacteria, and Betaproteobacteria were dominant bacterial groups.
• N+V fertilization and straw retention significantly altered the relative abundance of Acidobacteria, Actinobacteria, Gammaproteobacteria, and Verrucomicrobia.
• Actinobacteria responded strongly to straw retention, while Acidobacteria subgroup 7 and Opitutae (Verrucomicrobia) were linked to soils without straw.

Conclusions:

• Soil microbial biomass (MB-C, MB-N) is sensitive to changes in soil chemical factors and gas emissions induced by N+V amendments.
• Specific bacterial taxa, including Acidobacteria, Actinobacteria, and Verrucomicrobia, act as effective early-warning indicators for N+V amendments and straw retention.
• These findings highlight the potential for using microbial indicators to monitor the impact of soil management practices on sugarcane-cultivated soils.