Objective The high-throughput absolute quantitative method was used to explore the effect of modified materials on the bacterial community structure of saline-alkali soil, which could make up for the deficiency of relative quantification in studying the changes of bacterial community in saline-alkali soil.

Method A field experiment was conducted with maize as the test crop, five treatments were set up: CK (blank control), T1 (desulfurization gypsum 15 t hm⁻²), T2 (soil amendment 15 t hm⁻²), T3 (organic fertilizer 7.5 t hm⁻²) and T4 (desulfurization gypsum 7.5 t hm⁻² + soil amendment 7.5 t hm⁻² + organic fertilizer 3.75 t hm⁻²). After 84 days of maize planting, the absolute abundance, diversity and community structure of soil bacteria were determined by high-throughput absolute quantitative technique.

Result The application of modified materials could reduce soil pH and salt content. Among them, T4 treatment had the most significant effect on reducing pH, which was 0.44 units lower than CK (P < 0.05). The application of modified materials increased the contents of soil available phosphorus (AP), available potassium (AK), soil organic matter (SOM) and alkaline hydrolysis nitrogen (AN). The contents of AP, AK, SOM and AN in T4 treatment increased by 59%, 41.59%, 25.44% and 47.51%, respectively, compared with CK (P < 0.05). The results of absolute quantitative analysis showed that Proteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria and Chloroflexi were the dominant bacteria. The application of modified materials increased the richness and diversity of soil bacterial community. The copy number of bacterial 16S rRNA gene was significantly higher than that of CK, and T4 treatment was better than other modified treatments in increasing the copy number of bacterial 16S rRNA gene. The results of correlation analysis showed that the dominant groups of soil bacteria (phylum level and genus level) were positively or significantly positively correlated with AP, AK, SOM and AN, but negatively correlated with pH and salt content.

Conclusion The application of modified materials reduced the pH and salt content of saline-alkali soil, and increased the soil nutrient content, bacterial diversity and absolute number. The introduction of high-throughput absolute quantitative methods to carry out research can make up for the defects of relative abundance in characterizing microbial communities. Therefore, it has certain potential in elucidating many outstanding problems in micro-ecology, and this technology can be introduced into the study of soil microbial communities.