Impact of Biochar and Bioorganic Fertilizer on Rhizosphere Bacteria in Saline–Alkali Soil

Biochar and bioorganic fertilizers (BOF) that are used in agriculture can, both directly and indirectly, impact rhizosphere soil microorganisms. However, changes to the halophyte rhizosphere bacterial community after applying biochar and BOF to saline–alkali soil have not been thoroughly described. This study has investigated the bacterial communities of halophytes in saline–alkali soil through the addition of different biochar and BOF formulas using Illumina-based sequencing of the 16S rRNA gene fragment. B_BOF (biochar and BOF combined application) had the best effect, either by promoting the plant growth or by improving the physical and chemical properties of the soil. The concentration of the rhizosphere bacterial communities correlated with the changes in soil organic matter (OM) and organic carbon (OC). Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteria accounted for >80% of the total bacteria in each treatment. In addition, the abundance of Micromonospora was much higher in response to B_BOF than to the other treatments. BOF, with or without biochar, significantly influenced the bacterial community composition in the saline–alkali soil. The OC, OM, total nitrogen, and the available phosphorus had significant effects on the bacterial structure of this soil. The complex correlation of the bacterial communities between CK and B_BOF was higher compared to that between CK and FB or between CK and BOF. These findings suggested that the plant growth, the soil characteristics, and the diversity or community composition of the rhizosphere bacteria in saline–alkali soil were significantly influenced by B_BOF, followed by BOF, and then biochar; fine biochar had a stronger effect than medium or coarse biochar. This study provides an insight into the complex microbial compositions that emerge in response to biochar and BOF.