Halotolerant PGPB Delivered by Drip Irrigation Improve Crop Yield and Quality Through Changes in the Soil Bacterial Community

Halotolerant plant growth-promoting bacteria (PGPB) have great potential for alleviating salinity stress in crops. However, the current methods used with these bacteria are typically based on one-time inoculations, including soil basal application, seed dressing and plant infestation, all of which make it difficult to guarantee the desired plant effects. Here, we investigated the effects of seven halotolerant PGPB individually applied through a drip irrigation system in small quantities and at high frequency during the plant’s growth period on the soil physicochemical properties, plant agronomic performance and bacterial community in saline soil. Our findings revealed that drip irrigation with halotolerant PGPB notably decreased the soil pH and electrical conductivity while increasing the yield and fruit quality of jujube plants. Specifically, the Bacillus licheniformis (BL) and Bacillus mucilaginous (BM) treatments outperformed the control (no PGPB irrigation) by increasing the yield and vitamin C (VC) content by 23% and 22%, respectively. Additionally, the presence of halotolerant PGPB enriched the diversity of the bacterial community in the jujube rhizosphere and increased the relative abundance of beneficial bacterial groups at both the phylum (e.g., Cyanobacteria and Nitrospirota) and genus (e.g., Psychrobacter, Flavobacterium, and Steroidobacter) levels. Bacterial interactions, represented by co-occurrence networks, were more complex in the treatments involving PGPB irrigation, contributing to the transformation of the network keystones involved in soil nutrient cycling. Applications of BL, Bacillus cereus (BC), and BM reduced the soil salinity and increased the soil available nutrient contents and plant antioxidant enzyme activities, alleviating salinity stress and resulting in increases in crop yield and quality. This study highlights the feasibility and efficiency of applying halotolerant PGPB via drip irrigation in saline soil environments, thereby enhancing crop performance under salt stress.