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

Authors: ALVAREZ, ADRIANA - University Of Minnesota; Weyers, Sharon; GARDNER, ROBERT - University Of Minnesota

Submitted to: Biology and Fertility of Soils
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2022
Publication Date: 1/1/2023
Citation: Alvarez, A.L., Weyers, S.L., Gardner, R.D. 2023. Insights into the effect of cyanobacterial inoculations on the microbial dynamics of an arable soil under simulated rain. Biology and Fertility of Soils. 59:103-116. https://doi.org/10.1007/s00374-022-01686-1.
DOI: https://doi.org/10.1007/s00374-022-01686-1

Interpretive Summary: Cyanobacteria are potential biofertilizers. Fundamental knowledge gaps including effects on different types of soil and agroecological regions still limit their application. Researchers from Morris, MN, along with the University of Minnesota studied the effects of cyanobacterial inoculation to a nutrient-rich arable soil from the US Upper Midwest on soluble nutrients and microbial dynamics when subjected to repeated high intensity rainfall simulations. Increased soluble nutrient availability with cyanobacterial inoculations was linked to improved microbial biomass and activity. These findings demonstrate the potential of using cyanobacteria to improve soil fertility and resiliency of arable soil exposed to extreme weather conditions. This research is useful for researchers and land managers seeking to use renewable resources to enhance agricultural sustainability.

Technical Abstract: Intensive agriculture leads to deterioration of soil quality and strategies that improve soil function are a critical need. Projected increase of heavy rainfall with climate change might impact agricultural activity. Cyanobacteria are renewable resources for agriculture that provide organic matter to soil and enhance soil quality indicators. This study evaluated effects of inoculations with a N2-fixing cyanobacterium (Anabaena cylindrica) on nutrient and microbial dynamics of an arable Mollisol under simulated high intensity rainfall. Inoculated and non-inoculated pots (controls) were incubated for 14 days and then subjected to three rain events in one 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 nitrogen (SolN) and organic carbon (SolC), microbial biomass carbon (MBC) and nitrogen (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.