Effects of inoculation with Bacillus strains and their synthetic microbial communities on the growth and nitrogen and phosphorus uptake of soybean under low phosphorus stress

【Objective】 This study aimed to evaluate phosphate-solubilizing ability and growth-promoting effects of 3Bacillus strains and their synthetic microbial communities,and thereby provide theoretical basis for developing microbial fertilizers to alleviate low phosphorus stress and increase yield in soybean. 【Method】 Three Bacillus strains B1（Bacillus aerophilus）,B2（Priestia aryabhattai）,B3（Bacillus velezensis） and their synthetic microbial communities（B1 + B2,B1 + B3,B2 + B3,or B1 + B2 + B3） were firstly used as the tested strains to assess phosphate-solubilizing ability. Pot culture with low phosphorus stress was further conducted with 8 inoculation treatments, which were the non-inoculation control（CK）, 3 treatments of single inoculation with Bacillus strains（B1,B2,B3）, and 4 treatments of inoculation with synthetic microbial communities of Bacillus strains（B1 + B2,B1 + B3,B2 + B3,B1 + B2 + B3）,to determine plant height,plant dry weight,nitrogen and phosphorus uptake,leaf SPAD value,root traits（total root length,root surface area,average root diameter,root volume）,and the abundance of Bacillus strains in the rhizosphere. 【Result】 Three Bacillus strains and their synthetic microbial communities exhibited strong phosphate-solubilizing ability. Among them,the B1 + B3 combination exhibited the strongest phosphate-solubilizing ability. The results from pot culture showed that under low phosphorus stress conditions,inoculation with 3 different Bacillus strains and their synthetic microbial communities all significantly increased plant height,shoot and root dry weight,shoot and root nitrogen and phosphorus uptake（P＜0.05, the same below）, and improved root traits in soybean. Among them,the B1 + B3 combination exhibited the most pronounced growth-promoting effect. Compared with CK,soybean plant height significantly increased by 64.42%, shoot and root dry weights significantly increased by 208.08% and 209.68%,total root length,root surface area,average root diameter and root volume of soybean significantly increased by 110.97%,284.93%,40.39% and 361.69% respectively. Meanwhile,shoot and root nitrogen uptake significantly increased by 94.41% and 248.24%,and shoot and root phosphorus uptake significantly increased by 391.55% and 436.04% respectively. However,the inoculation with B1 + B2 + B3 combination did not exhibit growth-promoting effects compared with co-inoculation of 2 strains. Additionally, the inoculation of Bacillus strains also accordingly promoted its colonization in the rhizosphere of soybean.【Conclusion】 Inoculation with 3 Bacillus strains and their synthetic microbial communities all promotes soybean growth,and increases nitrogen and phosphorus uptake under low phosphorus stress. The B1 + B3 combination demonstrates fine inoculation effects,indicating the possible potential for developing synthetic microbial fertilizers.