Microbial consortia inoculants stimulate early growth of maize depending on nitrogen and phosphorus supply

Abstract

Adoption of microbial consortia as plant growth-promoting microorganisms (PGPMs) instead of single-strain inoculants is discussed as an approach to increase the efficiency and flexibility of PGPM-assisted production strategies. This study provides the functional characterisation of a commercial microbial consortia product (MCP) in a series of greenhouse experiments with maize on a silty-loam field soil (pH 5.9). A 60%-increased abundance of bacteria that could be cultivated after rhizosphere extraction was measured after MCP inoculation at the end of the 42-days culture period. MCP inoculation did not stimulate shoot biomass production of maize fertilised with nitrate, but growth improvement was recorded in combination with stabilised ammonium, especially with reduced phosphorus (P) supply. The MCP inoculant improved the acquisition of ammonium-N but also increased shoot-P. MCP inoculation stimulated root length development under reduced P supply with stabilised ammonium by 52%. This was accompanied by the increased auxin production capacity of rhizosphere bacteria. C-, N-, and P-turnover in the rhizosphere were little affected by the MCP inoculation, as deduced from the analysis of activities of extracellular soil enzymes. The findings suggest that the form of N supply is crucial for the efficiency of plant-MCP interactions.