Response of distinct soil types to cyanobacterial biofertilizer inoculation

Abstract Cyanobacterial biofertilizers provide soil fertility and productivity gains at varying levels in rice cultivation. The influences of distinct soil types with the characteristic composition of native cyanobacteria on the colonization of introduced strains remain largely unknown. In this work, seven soil types with the composition of indigenous cyanobacteria described by amplicon sequencing were inoculated with the cyanobacterial biofertilizer. The cyanobacterial growth was evaluated under light-dark and continuous dark cycles using marker-gene-based assays. The copies of cyanobacterial-16S rRNA gene markers varied from 5.65 × 10 6 to 9.22 × 10 7 g − 1 soil, and their abundance increased significantly in the soils with inoculant. The soils of KAR (Karnal, Typic Natrustalf) and IARI (Indian Agricultural Research Institute, Typic Haplustepts) showed the highest abundances of cyanobacteria under both light-dark and continuous dark cycles on 15 days after incubation (DAI) and 30 DAI. On 30 DAI, the cyanophage population in the soils tested ranged from 3.04 × 10 8 to 9.24× 10 8 g − 1 soil. The beneficial marker traits of C- ( cbbL ) and N ( nifH ) cycles and overall microbial abundances (bacteria, archaea, cyanobacteria, and cyanophage) showed a strong and positive correlation with the soil inoculation. At the same time, those genes related to nitrification and denitrification were clustered more closely in the uninoculated soils. These results indicate the potential for cyanobacterial biofertilizers to improve microbial contribution, in a soil-specific way, to fertility gains.