Effects of microalgal biomass as biofertilizer on the growth of cucumber and microbial communities in the cucumber rhizosphere

In the present study, microalgal biomass (Anabeana circinalis and Scenedesmus quadricauda) was used as biofertilizer in cucumber cultivation. The response of cucumber growth characters to microalgal biofertilizer was evaluated. Moreover, rhizosphere microbial diversity and community composition of cucumber was analyzed through 16S rRNA high-throughput Illumina sequencing data. The results showed that microalgal biomass as biofertilizer significantly promoted height, number of leaves and flower buds, and stem diameter of cucumber. The application of a high concentration of S. quadricauda to soil raised the diversity of rhizosphere fungi of cucumber. The rhizosphere microbial community of cucumber also responded to microalgal biofertilizer. The most abundant bacterial phylum in all samples was Proteobacteria. Acidobacteria, Actinobacteria, and Gemmatimonadetes were also highly abundant in all samples. Ascomycota was the most predominant fungal phylum in all samples. Zygomycota was the dominant phylum in the control, whereas Basidiomycota was dominant in all treatments. At the genus level, both growth-promoting bacteria and fungi (Azotobacter, Bacillus, Pseudomonas, Cryptococcus, Fusarium, Penicillium, and Trichoderma) from the rhizosphere of cucumber were enhanced in all treatments after the application of microalgae fertilizer. All results indicate a significant impact of microalgal biofertilizer on the growth of cucumber and microbial abundance in the cucumber rhizosphere.