Co-inoculation of compost with arbuscular mycorrhizal fungi and endophytic bacteria to alleviate the adverse impact of drought stress in maize

<p>Drought is a major abiotic factor limiting agricultural ecosystem productivity in arid and semi-arid areas. This study aims to evaluate the role of biostimulants in mitigating the adverse effect of water stress (well-watered (WW): 75% field capacity (FC) and drought-stressed (DS): 25% FC) through the application of single or combined biostimulants based on two microbial consortia (P: <em>Bacillus subtilis</em> and <em>Bacillus</em> sp., M: native arbuscular mycorrhizal fungi) and organic amendment (C) to <em>Zea mays</em> L. The metabolism of exposed plants to DS was negatively modified, affecting growth, mycorrhizal symbiosis, biochemistry, physiology, and mineral nutrition of the maize plants and also generated changes in the soil properties. Furthermore, biostimulants, particularly CM, improved shoot and root dry biomass by 179 and 275%, respectively, compared with control plants under DS. However, under 25% FC, shoot height and root length were stimulated by PC (68%) and P (37%) compared with the controls. Root mycorrhization was more intense when soil contained P and inhibited when it was amended with C under DS. The single/combined application of biofertilizers enhanced stomatal conductance, osmolytes (proline and total soluble sugars), antioxidant system (Polyphenol oxidase), and leaf mineral composition (K, Fe, S, Ca, Mn, and Zn) compared with untreated plants. On the other hand, stress markers content (malondialdehyde and hydrogen peroxide) were reduced by CMP treatment (67% and 18%, respectively). Biostimulants (C and/or P and/or M) modified soil quality by improving total organic matter, available phosphorus, nitrogen, K, Si, Ca, Fe, S, Mn, and Zn. In conclusion, the strategy of combining biostimulants could be an ecological solution in degraded agricultural soils in arid and semi-arid regions to protect maize crops against drought.</p>