Rhamnolipids amendment improves soil properties and enhances microecological functions in the saline-alkali soil

Abstract

A laboratory-scale study was conducted to investigate the effect of rhamnolipids (RLs) supplement on the amelioration of saline-alkali soils. The RLs supplement improved the soil aggregates stability and promoted the formation of macro-aggregates which increased by up to 10.84% and 15.92% in alkaline soil and saline soil, respectively. In addition, RLs amendment led to a pH reduction from initial 8.87 to 7.80–7.84 in alkaline soil, and a salt rejection up to 20.72% in saline soil, remarkably alleviating the saline-alkali stress on microorganisms and plants. Meanwhile, microbial growth and activity as well as the seed germination performance were greatly improved in both types of soil. Furthermore, RLs addition greatly altered the microbial community structure and supported the proliferation of bacterial species (e.g., <i>Pseudomonas oleovorans</i>, <i>Pseudomonas stutzeri</i>, and <i>Alcanivorax dieselolei</i>) that favored the improvement of soil properties and nutrients circulation, thus markedly enhancing the microecological functions including carbon and nitrogen metabolisms. Further supplement of γ-PGA only exhibited promoting effect on aggregates formation and microbial growth and activity. The findings obtained in this study prove the application of RLs as a promising approach for saline-alkali soil amelioration.