Microbial biomass, metabolic functional diversity, and activity are affected differently by tillage disturbance and maize planting in a typical karst calcareous soil

Abstract

Cultivation can affect soil microbial activities, with consequences for microorganisms that metabolize soil organic carbon and release CO2 to the atmosphere. Nevertheless, there is limited understanding of the short-term effects that tillage disturbance, maize planting, or their interactions exert on microbial biomass and metabolic function in a typical karst calcareous soil. A 1-year simulation experiment quantified the impacts of tillage disturbance and maize planting on soil microorganisms. Four treatments (2 × 2 m plot size), comprising conventional tillage with (CTM) and without maize (CT), and non-tillage with (NTM) and without (NT) maize, were conducted. Microbial biomass carbon (MBC), carbon metabolic function (Biolog profiles), CO2 flux, soil organic carbon (SOC), and dissolved organic carbon (DOC) were measured after 1-year tillage disturbance and maize planting. DOC was significantly lower in CTM, NTM, and CT than in NT, but SOC was slightly higher in NTM than in CTM and NT. Annual cumulative CO2 fluxes were significantly higher in CTM and NTM than in CT, which in turn was significantly higher than NT. Principal component analysis (PCA) suggests microbial community catabolic function differs in all treatments. CT showed significantly decreased MBC compared with NT, but significantly increased microbial metabolic activity and Simpson index (D). Compared with NT, NTM showed significantly increased microorganism metabolic activity, Shannon index (H), and D, but no significant difference in MBC. The interactions between maize planting and tillage disturbance had no significant effect on MBC or metabolic function diversity. Microbial biomass appears sensitive to tillage disturbance, while microbial metabolic activity is sensitive to maize planting. Maize planting with no tillage would increase CO2 emissions through enhanced microbial activity, but, at the same time, mitigate SOC loss due to an increase in C input by crop residues and roots left in the soil.