ABSTRACT
The demand for chemical fertilizers in agriculture has increased to deal with the present global population increase. However, the excessive use of chemical fertilizers can be reduced by applying biofertilizers as an eco-friendly tool. Plant growth-promoting rizobacteria (PGPR) has an essential need in terms of fertilizer savings and promoting plant yield. Here, we study the effect of using three (PGPR) bacterial strains “Bacillus nakamurai MSRH1, Bacillus pacificus MSRH3, Paenibacillus polymyxa MSRH5”, integrated with chemical fertilizers (40, 60, 80, 100% need based NPK) on vegetative growth, yield production, and quality of table grapes ‘Flam Seedless’ grown in sand soil during two successive seasons of 2020 and 2021, with a preliminary trial season in 2019. Our results show that amending grapes with NPK in combination with the consortium of three strains led to significant improvement in colonized vines compared to a single application of 100% NPK. Results showed that bacterial consortium combined with 80% and 60% NPK mineral fertilizer had more positive effects than un-inoculated vines in growth parameters, cluster characteristics, yield/vine and berry quality in the two growing seasons. Besides, N, P and K concentrations of leaf petiole, total leaf chlorophyll content, and carbohydrates in canes were significantly enhanced by bacteria consortium with 80% and 60% PK chemical fertilizers. PGPR significantly increased total bacterial count, N2-fixing, P- solubilizing and K-solubilizing bacteria in soil treated with the three strains of bacteria plus mineral fertilizer. In addition, dehydrogenase and phosphatase activity in the rhizosphere soil were also increased in treatments inoculated with strains plus mineral fertilizer. The field study results showed that PGPR approach has potential and can be considered as a crop management strategy to increase the yield and quality of grapes, reduce chemical fertilization and subsequent environmental pollution, and could be useful in terms of sustainable production.