Growth, Yield, and Photosynthetic Dry Matter Remobilization Response of Barley to Plant Growth Promoting Rhizobacteria (PGPR) and Nitrogen

A two-year factorial experiment based on a randomized complete block design with three replicates was carried out on barley cultivar LB-IRAN at the research farm of the Islamic Azad University, Ardabil, Iran, during the cropping years of 2019–2021, in order to survey the impact of plant growth-promoting rhizobacteria (PGPR) and nitrogen fertilizer on growth, yield, and remobilization of photosynthetic dry matter in barley. The first factor included five nitrogen levels: 0 (control), 25, 50, 75, 100 kg/ha net nitrogen; the second factor contained grain inoculations with four bacteria: no inoculation (control), Azotobacter chroococcum race 5, Azospirillum lipoferum race of, and a combination of the two mentioned bacteria. Fertilization was performed at the planting, tillering, and grain filling stages. Results revealed that the number of plant/m2, tiller per plant, 1000 grain weight, grain per spike, grain yield per unit area, biological yield, rate of dry matter remobilization from stem to the grain, contribution of dry matter remobilization from stem to the grain, rate of remobilization from whole of the plant to the grain, contribution of remobilization from whole of the plant to the grain, single grain weight, and harvest index significantly increased. Nitrogen rate increment resulted in the higher rates of the above-mentioned traits as 100 kg/ha nitrogen significantly showed the highest amounts while control showed the least. Combined treatment of the bacteria resulted in a higher rates as compared to the single bacteria, and the control showed the lowest amounts. It was also observed that application of 100 kg/ha nitrogen on Azotobacter chroococcum race 5 and Azospirillum lipoferum race of resulted in the lowest rate of dry matter remobilization from the stem and whole plant to the grain as well as the contribution of dry matter remobilization from the stem and whole plant to the grain, while control treatments of nitrogen and of PGPRs caused the highest rates. Difference between the highest and lowest rates of grain yield was observed by applying nitrogen (24%) and PGPRs (40%).