Microbial Biomass Carbon in Different Sugarcane Cultivation Systems

Sugarcane is an economically important crop in Brazil and is widely cultivated in the Cerrado. This study aimed to evaluate microbial biomass carbon (MBC) in soils under different sugarcane cultivation systems in the Goianésia region, Goiás, Brazil. Conventional and organic systems were compared, with and without vinasse application, at three cutting ages (2nd, 4th, and 6th cuts).

Soil samples were collected at depths of 0–10 cm and 10–20 cm and analyzed in the laboratory using the irradiation-extraction method proposed by Islam & Weil (1998). Overall, the organic system presented higher MBC values at both depths, with averages of 356 mg C/kg soil (0–10 cm) and 278 mg C/kg soil (10–20 cm), compared to 241 mg C/kg and 198 mg C/kg in the conventional system, respectively.

The application of vinasse significantly increased MBC levels regardless of the evaluated depth. Soils receiving vinasse showed averages of 384 mg C/kg soil (0–10 cm) and 312 mg C/kg soil (10–20 cm), in contrast to 229 mg C/kg and 185 mg C/kg in plots without vinasse. This effect is attributed to the higher input of organic matter provided by vinasse, which stimulates microbial activity.

No statistically significant differences in MBC were observed among the different cutting ages at the 0–10 cm depth, likely due to the time required for changes in organic matter to be reflected in microbial biomass. However, at the 10–20 cm depth, the 6th cut showed lower MBC values (224 mg C/kg) compared to the 2nd and 4th cuts (289 mg C/kg and 298 mg C/kg, respectively), suggesting a potential depletion of organic resources with the advancement of cultivation cycles.

These results reinforce the importance of organic management and vinasse application in maintaining soil microbial biomass, contributing to the sustainability and health of sugarcane production systems in the Cerrado.