Combined application of microalgae and plant growth-promoting rhizobacteria improves Lactuca sativa growth

The extensive use of chemical fertilizers causes a detrimental effect on crop yields and soil crust. A potential alternative to chemical fertilizers is the use of plant beneficial microbes to manage nutrients and preserve soil function. In this study, pot experiments were conducted to assess the effects of the green algae Scenedesmus sp. SD07, the bacterium Pantoea agglomerans CAH6 and their combined application on the growth of Lactuca sativa and soil properties. The SD07, CAH6 and SD07 + CAH6 treatments significantly increased lettuce plant shoot length, shoot-fresh weight, shoot-dry weight, root length, root-fresh weight, root-dry weight, and photosynthetic pigments as compared to the control plants. Similarly, these biofertilizer treatments enhanced the uptake of essential nutrients by plant leaves, including N 64–145%, P 35–90%, K 30–78%, Mg 25–74%, Fe 48–91%, and Zn 44–89%, as compared to the control. In comparison to the control, the plants inoculated with SD07, CAH6 and SD07 + CAH6 increased the level of soluble sugar, protein and phenolic content in their leaves by 44–91%, 59–104%, and 50–86%, respectively. Furthermore, in lettuce cultivation the soil inoculated with SD07, CAH6 and SD07 + CAH6 significantly increased the soil available nutrients of N (33–48%), P (47–106%) and K (19–38%), as well as acid phosphatase (32–65%), urease (19–56%) and β-glucosidase (23–52%) compared to the control treatment. Nevertheless, the results showed that the SD07 + CAH6 combined inoculation treatment had the most beneficial effects on increasing lettuce plant biomass, nutrient uptake and soil fertility. Thus, our study highlighted the potential of SD07 + CAH6 as an eco-friendly biofertilizer to promote sustainable agriculture.