Synergistic effects of PGPR and organic fertilizer on soil fertility, enzyme activities, and microbial community composition in saline-alkali rice systems

Soil salinization presents a significant global challenge to agricultural productivity and food security. This study explores the synergistic effects of plant growth-promoting rhizobacteria (PGPR) and organic fertilizer in remediating saline-alkali soils for rice cultivation. Four salt-tolerant PGPR strains—Bacillus sp. RM-1/RM-2, Aspergillus sp. SV-1, and Penicillium sp. SV-2—were isolated from the rice rhizosphere in saline-alkali soils and combined with either sterilized (SOF) or unsterilized (UOF) cow manure compost. Rice cultivation experiments under mild (1.0 % Na₂CO₃) and moderate (1.5 % Na₂CO₃) salinity stress demonstrated that the UOF + PGPR treatment significantly improved soil fertility and enzyme activities during the grain-filling stage. Compared to the control, UOF + PGPR increased soil organic matter by 218.99 %, available potassium by 1036.20 %, available phosphorus by 563.13 %, catalase activity by 100.00 %, urease activity by 340.98 %, and sucrase activity by 251.03 % under moderate salinity conditions. Microbial community analysis revealed that PGPR combined with organic fertilizer reduced the abundance of Acidobacterium while increasing the relative abundance of Firmicutes, Bacteroidetes, and Ascomycota, leading to decreased soil salinity and enhanced soil nutrient content, ultimately improving rice productivity. This study introduces an innovative PGPR-organic fertilizer formulation that not only enhances native microbial functions but also reduces soil pH and soluble salt accumulation. However, the findings are currently limited to controlled pot experiments. Further research is necessary to validate these results in field conditions and assess long-term ecological impacts. We recommend large-scale field trials of the UOF + PGPR combination in salinized areas, the development of crop-specific PGPR consortia with drought resistance and heavy metal remediation properties, and the establishment of soil health monitoring protocols to track carbon sequestration and salt reaccumulation over time.