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Soil salinization is a global environmental concern due to its great restriction on land use efficiencies and crop production. Rhamnolipids demonstrate great potential in ameliorating soils and improving plant growth. However, the exact performance and underlying mechanisms still remain unclear. Herein, a field-scale study was conducted to investigate the effect of rhamnolipids addition on cotton growth in soils with different degrees of salinization (i.e., slightly, moderately, and highly salinized soils). The drip-irrigated rhamnolipids solution (300 mg/L) effectively reduced the salinity in rhizosphere soils, with desalination rates of 9.7 %, 4.5 %, and 2.5 % in slightly, moderately, and highly salinized soils, respectively, and mitigated the salt stress on cotton plants. The analysis of microbial community in highly salinized soils showed that the rhizosphere community was modified by the rhamnolipids, with enriched populations of plant growth-promoting fungi and decreased abundance of plant pathogens. Further investigation of functional genes related to carbon, nitrogen, sulfur, and phosphorus cycling suggested that the rhamnolipids efficiently drove the nutrient cycling and promoted the interconnection of functional microorganisms. The ameliorated soil environment and strengthened microecological functions led to the enhanced photosynthetic process and improved cotton growth and yield (up to 24.4 %). Our study is the first to demonstrate the feasibility of applying rhamnolipids to improve cotton growth in salinized areas and disclose the underlying mechanisms. [Display omitted] • Rhamnolipids supplement improved the growth and yield of cotton in salinized soils. • Rhamnolipids mitigated the salt stress in rhizosphere soils of cotton plants. • Rhamnolipids modified the rhizosphere community, especially the fungal community. • Rhamnolipids drove the nutrient cycles and improved microbial cooperation. • A feasible strategy for raising the cotton yield in salinized areas was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The BCOR can effectively remove pollutants from the oilfield produced water. • The first BCOR stage played a major role in pollutants removal. • The functional genera in pollutants removal were disclosed by correlation analysis. • Non-random co-occurrence and function-driven modular patterns were exhibited. The multistage bio-contact oxidation reactor (BCOR) is a widely used biological strategy to treat wastewater, however, little is known about the performance and microbial community information of BCOR during the treatment of low-COD and high-salinity oilfield produced water. In this study, the performance of a multistage BCOR in treating produced water was investigated. The result suggested the BCOR could efficiently remove COD, BOD 5 , NH 4 +-N, and oil pollutants. Besides, high-throughput sequencing analysis revealed that oil content was the main variable in shaping the community structure. The highest total relative abundance of potential pollutants degraders in first BCOR stage suggested significant role of this stage in pollutants removal. In addition, the correlation analysis disclosed the key functional genera during the degradation process, including Rhodobacter , Citreibacter , and Roseovarius. Moreover, network analysis revealed that the microbial taxa within same module had strong ecological linkages and specific functions. [ABSTRACT FROM AUTHOR]

Coastal regions face significant challenges in crop production due to soil salinization. Rhamnolipids and sophorolipids are prototypical glycolipid biosurfactants that exhibit considerable promise in soil amelioration and crop growth regulation. Nevertheless, the efficacy and mechanisms of these glycolipids in coastal saline-alkali soils remain poorly understood. In this study, a pot experiment was carried out to examine the impact of rhamnolipids and sophorolipid supplementation at different doses (i.e., 50, 100, and 200 mg/kg) on oleic sunflower growth. Both biosurfactants at appropriate doses effectively reduced the soil alkalinity, elevated the levels and bioavailability of soil nutrients (i.e., available nitrogen, phosphorus, and organic matter), and improved enzyme activities (i.e., catalase, urease, β-glucosidase, and alkaline phosphatase). Notably, the application of medium-dose rhamnolipids resulted in the most substantial enhancement of crop growth (up to 117 % increase in fresh weight). Besides, an appropriate dose of rhamnolipids enriched the beneficial microbiota (e.g., Glycomyces , Stachybotrys , and Mortierella) while inhibiting the growth of pathogens (e.g., Fusarium) in rhizosphere zones. Conversely, a high dose of sophorolipids accumulated plant pathogens in both the rhizosphere and bulk soils. Correlation-based network analysis and microbial function predictions revealed that the intervention of medium-dosed rhamnolipids enhanced the cooperation within bacterial and fungal communities and activated the community functions related to carbon and nitrogen cycling. Moreover, the increased soil enzyme activity was the main driver for improved crop growth in rhamnolipids-supplemented treatments. The findings provide new insights into the underlying mechanisms of glycolipids-assisted improvement of crop growth in coastal saline-alkali regions. [Display omitted] • The dose-effect relationship of typical glycolipids on crop growth was clarified. • Rhamnolipid more effectively improved crop growth in saline soils than sophorolipid. • Rhamnolipid mitigated alkali stress and increased nutrient availability. • Rhamnolipid modified rhizosphere community and improved microbial cooperation. • Increased soil enzyme activity was the key driver for improved plant growth. [ABSTRACT FROM AUTHOR]