High-nitrogen organic fertilizer promotes the growth of bermudagrass (Cynodon dactylon), zoysiagrass (Zoysia japonica) and paspalum grass (Paspalum vaginatum) by enhancing nitrogen use efficiency associated with Bacillus-stimulated bacterial community

In the process of lawn production and planting, the application of different fertilizers has a significant impact on the growth of turfgrass and the soil environment. It is well known that organic fertilizer can promote the growth of turfgrasses, but its underlying mechanism still needs to be further analyzed. In our study, pot experiment was conducted, where three commonly used warm-season turfgrass species, including bermudagrass (Cynodon dactylon, 'Yangjiang', YJ), zoysiagrass (Zoysia japonica, 'Suzhi No.1 ', S1) and paspalum grass (Paspalum vaginatum, 'Adalayd', AD), were planted for two growing seasons in PVC tubes with no fertilizer treatment (CK, sandy soil), chemical fertilizer treatment (CF, sandy soil with urea, Ca(H2PO4)2 & sdot;H2O and K2SO4), low-nitrogen organic fertilizer treatment (LNOF, sandy soil with chicken manure composts) and high-nitrogen organic fertilizer treatment (HNOF, sandy soil with oil rapeseed cake composts). Each PVC tube contained 16 stolons of each turfgrass with the apical two nodes, and each treatment had six biological replications. Phenotypic and physiological data were analyzed using SPSS Statistics (Duncan's test) and revealed that HNOF treatment significantly enhanced turfgrass growth, maintained soil fertility, and improved nitrogen use efficiency (NUE) of plants. Conversely, the effects of LNOF on turfgrass and soil were similar to those of CF. The Principal Coordinate Analysis (PCoA) based on the Bray-Curtis distance metric showed that the bacterial community were mainly influenced by different fertilization treatments, while the fungal community were more associated with the different turfgrass species. The structural equation modeling (SEM) analysis revealed that different fertilization treatments primarily affect NUE by influencing the composition of the bacterial community, which has a significant impact on the total fresh weight of the turfgrasses. The Linear discriminant analysis effect size (LEfSe) and correlation analysis revealed that HNOF treatment induced the most significant difference operational taxonomic units (OTUs), among which, Bacillus OTUs were the largest number and all Bacillus OTUs were positive related with the NUE and fresh weight of the plants. Furthermore, the functions of "chitinolysis", "aerobic chemoheterotrophy", "aromatic compound degradation" and "chemoheterotrophy" showed a significant positive correlation with NUE, and some Bacillus strains have been reported to explicitly possess these functions. This research highlights the benefits of HNOF in promoting turfgrass growth and maintaining soil fertility, with Bacillus potentially playing a crucial role in those process. Our findings further suggest that the combination of stimulated Bacillus and HNOF (bio-organic fertilizers) may have a synergistic effect in promoting the growth of warm -season turfgrass, which needs to be investigated in the future studies.