Sustainable Bioprocessing of Phosphate Sludge With a Plant Growth‐Promoting Rhizobacteria Consortium Enhances Drought Tolerance and Growth of Chia ( Salvia hispanica L.)

Abstract

Valorizing bacterial biomass and phosphate sludge derived from phosphate extraction byproducts supports the circular economy and provides a sustainable strategy for mitigating the growing impact of drought stress, a major constraint on crop productivity under climate change. The present study aimed to assess the potential of a bioformulated consortium of six PGPR to improve drought tolerance in chia ( Salvia hispanica L.) grown in pots containing soil amended with 5% phosphate sludge under semicontrolled greenhouse conditions and exposed to severe drought stress (25% field capacity) for 30 days. The results showed that PGPR inoculation significantly mitigated the adverse effects of drought stress by maintaining plant growth and physiological performance. Compared with noninoculated drought‐stressed seedlings, PGPR‐inoculated seedlings exhibited significant increases in shoot length (32.7%), leaf number (56.9%), and internode distance (31.0%). In parallel, soil bioavailable phosphorus increased by 19.7‐fold following inoculation compared with the noninoculated treatment. Moreover, PGPR‐inoculated seedlings showed significantly increased chlorophyl a and b contents and a decrease in osmolyte accumulation, including proline and soluble sugars, indicating improved photosynthetic performance and reduced osmotic stress. Overall, these findings demonstrate that the PGPR consortium enhances drought tolerance through synergistic effects on nutrient mobilization, plant growth, and stress regulation, supporting its use with phosphate sludge as a sustainable strategy for chia cultivation under arid and semiarid conditions.