Effect of micro–nano bubbles on the remediation of saline–alkali soil with microbial agent

The widespread distribution of saline–alkali soil around the world affects the health of ecological systems and the development of the national economy by limiting the growth of plants. However, the commonly used remediation technologies have the drawbacks of low efficiency, high cost, and secondary pollution. This study investigated the feasibility and efficacy of novel combined micro–nanobubbles (MNBs) and microbial agent (MA) technology for the remediation of saline–alkali soil. The results demonstrated that the combined MA–MNBs method greatly renovated the properties of saline–alkali soil compared with the technologies of single utilization of MA or MNBs process in the laboratory. The method resulted in a reduction of soil electrical conductivity and pH levels, an improvement in soil fertility, and the formation of soil aggregates. Moreover, the method significantly impacted the growth of plants, particularly in plant length, dry weight, and rhizome elongation. Further high–throughput sequencing and gene expression analysis revealed that the MA–MNBs method enhanced the abundance of soil microbial community compared with single MA and MNBs treatment. Gene enrichment analysis revealed that the MA–MNBs method could compensate for the shortcomings of single MA treatment and enhance the expression of energy metabolism and salt stress–related genes attributed to MNBs treatment, thereby significantly improving the growth and development of plants. Consistently, 6115 kg/ha of rice was yielded in the field for the saline–alkali soils using this MA–MNBs method, with zero crops before remediation. This study provided a novel, efficient, and green strategy for the remediation of saline–alkali soil without adding any chemicals.