TWO field experiments were carried out at Desert Research Center (D.R.C.), Agricultural Experimental Station at EL-Kharga, New Valley Governorate, during the two summer growing seasons of 2010 and 2011, these experiments aimed to study the effect of biofertilization (Azotobacter chroococcum, Bacillus megatherium (PDB) and mixture of two isolates) and silicon spraying rates (200, 400, 600,800 and 1000 mg/L.) against control on the productivity of Sunflower (Helianthus annuus L.) by using cultivar Sakha 53. The experiments were laid out in a split-plot design with four replicates. Foliar application of silicon treatments was arranged in the main plots and biofertilization treatments in the sub-plots.
Results showed that both spraying silicon and biofertilization treatments had an enhancement effect on plant height, number of leaves, leaves surface area, fresh and dry weight of leaves/plant and stem diameter, also head diameter, seeds number/head and 100-seed weight as well as seed and straw yields. Moreover, seed oil percentage and oil yield. The enhancement effect of all above-mentioned traits with inoculation of Azotobacter chroococcum, PDB individual or mixed compared with the control treatment (without biofertilization). Also, a remarkable influence of the interaction between silicon foliar application and biofertilization treatments on all yield and yield components. Results also indicated significant microbial activity in rhizosphere soil expressed by total microbial counts, CO2 evolution, Azotobacter and Phosphate dissolving bacteria counts and Enzymatic activities (Dehydrogenase,Nitrogenase and Phosphatase) exhibited a positive response in all treatments compared to uninoculated control.