Co-application of wood ash and Paenibacillus mucilaginosus to soil: the effect on maize nutritional status, root exudation and composition of soil solution

Abstract

Improvement in nutrient efficiency of recycled fertiliser products represents a crucial step for sustainable agriculture. In this context, ash from biomass combustion belongs to the materials of interest. Novel strain of potential plant growth-promoting bacterium (Paenibacillus mucilaginosus ABi13) was tested for its ability to increase the plant availability of nutrients from wood ash (WA) in P-deficient soil-plant systems. Maize plants were grown in soil microcosms in semi-natural conditions, enabling rhizospheric- and bulk-soil solution analysis with special emphasis on low-molecular-mass organic acids (LMMOA). Wood ash, as a sole fertiliser, increased biomass yield and improved nutritional status of maize plants. Concomitantly, application of WA led to lower root exudation rates of malate and isocitrate likely due to improved P status of plants. P. mucilaginosus ABi13 was inefficient in mobilising P from plain, acidic soil, but increased P solubility in ash-amended soil. However, P. mucilaginosus ABi13 consequently decreased NO3− concentrations in soil solution and induced N deficiency in maize, which led to decreased biomass yield and LMMOA exudation rates. This study demonstrated the importance of plant nutritional status on the final outcome of PGPR inoculation and contributes to our understanding of interactions between introduced PGPR, soil microbiome and plants.