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

Abstract

This study focused on the effects of organic and inorganic amendments and straw retention on the microbial biomass (MB) and taxonomic groups of bacteria in sugarcane-cultivated soils in a greenhouse mesocosm experiment monitored for gas emissions and chemical factors. The experiment consisted of combinations of synthetic nitrogen (N), vinasse (V; a liquid waste from ethanol production), and sugarcane-straw blankets. Increases in CO2-C and N2O-N emissions were identified shortly after the addition of both N and V to the soils, thus increasing MB nitrogen (MB-N) and decreasing MB carbon (MB-C) in the N+V-amended soils and altering soil chemical factors that were correlated with the MB. Across 57 soil metagenomic datasets, Actinobacteria (31.5%), Planctomycetes (12.3%), Deltaproteobacteria (12.3%), Alphaproteobacteria (12.0%) and Betaproteobacteria (11.1%) were the most dominant bacterial groups during the experiment. Differences in relative abundance of metagenomic sequences were mainly revealed for Acidobacteria, Actinobacteria, Gammaproteobacteria and Verrucomicrobia with regard to N+V fertilization and straw retention. Differential abundances in bacterial groups were confirmed using 16S rRNA gene-targeted phylum-specific primers for real-time PCR analysis in all soil samples, whose results were in accordance with sequence data, except for Gammaproteobacteria. Actinobacteria were more responsive to straw retention with Rubrobacterales, Bifidobacteriales and Actinomycetales related to the chemical factors of N+V-amended soils. Acidobacteria subgroup 7 and Opitutae, a verrucomicrobial class, were related to the chemical factors of soils without straw retention as a surface blanket. Taken together, the results showed that MB-C and MB-N responded to changes in soil chemical factors and CO2-C and N2O-N emissions, especially for N+V-amended soils. The results also indicated that several taxonomic groups of bacteria, such as Acidobacteria, Actinobacteria and Verrucomicrobia, and their subgroups acted as early-warning indicators of N+V amendments and straw retention in sugarcane-cultivated soils, which can alter the soil chemical factors.

Dominance of bacterial ammonium oxidizers and fungal denitrifiers in the complex nitrogen cycle pathways related to nitrous oxide emission

“…This cascade is further reinforced by N fertilization, especially when N is applied with a rich carbon source, such as vinasse (Di et al., ). Previous studies of sugarcane fields have shown that high N 2 O fluxes occur immediately after N fertilization (Carmo et al., ; Navarrete et al., ; Pitombo et al., ; Soares et al., , ). However, denitrification appears to be less important than AOB for N 2 O emissions under our experimental field conditions.…”

Disentangling the influence of earthworms in sugarcane rhizosphere

“…The samples were taken all in the morning around 10:00 h, and the time in between the samplings were as follows: the first 16 samplings were taken using an interval of ~7 days, after that, 3 samplings used an interval of ~10 days, and the following 2 samplings used an interval of ~15 days with the last one taken using an interval of ~30 days. N 2 O and CO 2 were determined using gas chromatography (SRI 8610 C Model, Torrance, CA, USA) configured with the same analytical conditions as described elsewhere65 (HayeSep-D and N- packed columns at 81 °C). Average of concentrations was calculated as follows: the values of concentrations measured along the experiment were summed and divided by the number of samplings (Figs 2a and 3a).…”

Agronomic and environmental implications of sugarcane straw removal: a major review

“…Recently, there have been efforts to characterize the microbial groups responsible for the soil activities under various management practices in sugarcane cropping areas (Navarrete et al ., ; Pitombo et al ., ; Rachid et al ., ). Rachid et al .…”