Effect And Mechanism Of Bacteria-microalgae Collaboration On The Improvement Of The Yellow River Delta Soil

Saline-alkali soil seriously affects crop growth due to problems such as high salinity,high p H,and imbalanced proportions of essential plant nutrients.Using microorganisms to improve saline-alkali soil and promote crop growth is an environmentally friendly and effective method,but there is also the problem of single microbial functions and poor effects.The synergy of bacteria and microalgae can fully exert the synergistic effect of bacteria and algae and improve their effects on soil and crops,but the effect of bacteria-microalgae synergy on saline-alkali soil improvement and crop promotion is currently unclear.In this study,one inorganic phosphate solubilizing fungus(Aspergillus niger),one organic phosphate solubilizing bacterium(Paenibacillus xylanexedens),one potassium solubilizing bacterium(Paenibacillus sabinae),and one salt tolerant microalga(Leptolyngbya sp.RBD05)were selected from the coastal saline-alkali soil in the Yellow River Delta,and applied them to saline-alkali soil to investigate the effects of different fungus-microalga or bacteria-microalgae synergies on soil properties,microbial communities,wheat growth,and wheat stress tolerance.(1)Single strain of fungus,bacteria,or microalga,as well as combinations of different fungus-microalga and bacteria-microalga,were applied to saline-alkaline soils without wheat cultivation,and the changes in soil quality and microbial communities were investigated.The results showed that the groups with the best effects on soil available nitrogen,available phosphorus,organic carbon,sucrase activity,urease activity,and alkaline phosphatase activity were Paenibacillus xylanexedens(P.xylanexedens)+ Leptolyngbya sp.RBD05,Aspergillus niger(A.niger),Paenibacillus sabinae(P.sabinae)+ Leptolyngbya sp.RBD05,Leptolyngbya sp.RBD05,P.sabinae,and P.sabinae + Leptolyngbya sp.RBD05,respectively.These groups exhibited a significant increase of 24%,58%,46%,25%,25%,and 23%respectively,compared to the control group.The groups with the best effects on reducing soil p H and electrical conductivity(EC)were the A.niger group and A.niger+ Leptolyngbya sp.RBD05,which showed a significant decrease of 4% and 68%,respectively,compared to the control group.The synergy on the improving soil available nitrogen,organic carbon,alkaline phosphatase activity,and soil electrical conductivity was more significant.Compared to the control group,both the combinations of A.niger and Leptolyngbya sp.RBD05 and P.sabinae and Leptolyngbya sp.RBD05 decreased the diversity and abundance of soil microbial communities.The combinations of P.xylanexedens and Leptolyngbya sp.RBD05 reduced the diversity of soil microbial communities,but increased their abundance.(2)Single strain of fungus,bacteria,or microalga,as well as combinations of different fungus-microalga and bacteria-microalga,were applied to wheat pot experiment,and the changes of saline-alkali soil properties under the interaction of microbe,soil and plant were investigated.The results showed that the groups with the best effects on soil available nitrogen,available phosphorus,and available potassium were A.niger + Leptolyngbya sp.RBD05,P.xylanexedens + Leptolyngbya sp.RBD05,and P.xylanexedens + Leptolyngbya sp.RBD05,respectively.The synergy on the improving soil available nitrogen,available phosphorus,and available potassium in wheat pot experiment was more significant.(3)Single strain of fungus,bacteria,or microalga,as well as combinations of different fungus-microalga and bacteria-microalga,were applied to wheat pot experiment,and the changes of wheat growth indexes under the interaction of microbe,soil and plant were investigated.The results showed that the groups with the best effects on stem length,root length,fresh weight and dry weight of wheat were Leptolyngbya sp.RBD05,P.sabinae + Leptolyngbya sp.RBD05,P.xylanexedens +Leptolyngbya sp.RBD05,and P.sabinae + Leptolyngbya sp.RBD05,respectively.These groups exhibited a significant increase of 24%,70%,131%,and 85%respectively,compared to the control group.The groups with the best effects on increasing wheat nitrogen and phosphorus content and N:P ratio were P.xylanexedens,A.niger,and P.sabinae,respectively.A.niger + Leptolyngbya sp.RBD05.group had the best increasing effect on potassium content and K:Na ratio of wheat.P.xylanexedens group had the best effect on reducing wheat sodium content.The synergy of bacteria and microalgae on the improving stem length,root length,fresh weight,dry weight,potassium content,and K:Na ratio of wheat was more significant.Promoted by fungus,bacteria,microalga,and their synergistic effects,proline content and superoxide dismutase activity in wheat had significant changes,which had positive effects on improving wheat stress resistance.The changes in wheat malondialdehyde content further indicated that fungus,bacteria,microalga,and their synergistic effects could alleviate wheat stress.The synergistic effect of fungus-microalgae or bacteria-microalgae can fully leverage their respective advantages and have better effects on saline-alkali soil improvement and crop growth.This study provides a new method for using microbial technology to ecologically improve saline-alkali soil,promote crop growth in saline-alkali land,and enhance crop stress tolerance.