Potential application of Bacillus amyloliquefaciens EB13 inoculant for improving soil fertility and Citrus sinensis growth

The application of bacterial inoculants to suppress crop diseases and boost crop yields supports sustainable agriculture by reducing the use of chemical fertilizers and pesticides. Bacillus amyloliquefaciens EB13 inoculant was applied to citrus plants (Citrus sinensis) in the field to investigate the effect of strain EB13 treatment on soil fertility and citrus growth in non-sterile conditions. Two years old citrus tree transplanted into the polybag containing 10 kg soil was inoculated with EB13 culture and placed in the open field for six months. Soil enzyme activities were increased significantly (P<0.05) by EB13 inoculation, they are acid phosphatase activity (1848.82 to 2450.50 μg p-NP/g dry soil h), alkaline phosphatase activity (475.15 to 640.98 μg p-NP/g dry soil h), urease activity (147.89 to 306.55 μgNH4-N/g dry soil h), and total soil microbial activity (1.85 to 2.77 μg fluorescein/g h). Furthermore, the population of bacteria and fungi in the rhizosphere significantly (P<0.05) was increased by the EB13 inoculation. These improvements supported citrus growth by increasing fruit yield approximately threefold (5.33 to 18.33 fruits/plant). Our finding indicated that Bacillus amyloliquefaciens EB13 was able to associate well with citrus in the non-sterile condition and has a long-term positive effect on soil fertility and citrus growth.