Combined effects of soil amendments and nitrogen fertilizer on rice physiology, nutrient availability, and soil microbial communities under salt stress conditions

Soil salinization poses a major constraint on rice productivity. This study evaluated the integrative effects of three amendments (zeolite, coconut coir, and humic acid) combined with slow-release urea on rice growth, rhizosphere bacterial communities, and soil nitrogen dynamics under salt stress. Results demonstrated that zeolite, particularly when combined with slow-release urea, exhibited the most pronounced benefits. It significantly enhanced soil bacterial diversity and reshaped the community structure by enriching dominant taxa, with Acidobacteria and Gemmatimonadetes abundances increasing by 110–242% and 138–236%, respectively, compared with other treatments. These microbial shifts were strongly correlated with increased soil available nitrogen and total potassium. Functionally, zeolite improved rice photosynthetic rate by 13–67% and panicle K + content by 6–16%, while reducing whole-plant Na + accumulation by 2–20%. Consequently, this treatment consistently produced the highest grain yield. Our findings indicate that zeolite combined with slow-release urea optimizes the rhizosphere microenvironment and nutrient availability, thereby enhancing rice physiological performance and productivity under salt stress. This integrated strategy offers a promising approach for sustainable crop production.