Insights into the effect of cyanobacterial inoculations on the microbial dynamics of an arable soil under simulated rain.

The effects of inoculations with a N2-fixing cyanobacterium (Anabaena cylindrica) on nutrient and microbial dynamics of an arable Mollisol were studied under simulated high intensity rainfall. Inoculated and non-inoculated pots (controls) were incubated for 14 days and then subjected to three rain events in 1 week, followed by three weekly events for a total of six events. Soil samples at three depth layers (0–1, 5–6, and 10–11 cm) were taken at four time points: 1 day after inoculation, 14 days after inoculation, after rain 1, and after rain 6. Soil chlorophyll a (Chla), soluble fractions of N (SolN) and organic C (SolC), microbial biomass C (MBC) and N (MBN), microbial activity (FDA hydrolysis), and soil respiration (CO2 efflux) were determined. Results revealed depth-related changes in Chla, SolC, SolN, MBC, MBN, and FDA hydrolysis with greater effects at the surface layer (0–1 cm). Soil respiration varied with soil moisture and increased in inoculated treatments. After all rain simulations (49 days after inoculation), higher SolC, MBC, MBN, and FDA hydrolysis in surface soil of inoculated treatments indicated positive changes that persisted after consecutive rains. These findings suggest that cyanobacterial soil amendments might enhance soil quality and resiliency in agricultural soils exposed to high intensity rainfall. [ABSTRACT FROM AUTHOR]