Abstract

The ability of phosphate solubilizing bacteria (PSB) to convert insoluble forms of phosphorus to an accessible form is an important trait in sustainable farming for increasing plant yields. The beneficial effects of PSB on crop productivity have been widely described, but the use of PSB as biofertilizer is scarcely documented in sunflower. The objective of this study was to evaluate the effect of application of PSB, Bacillus M-13, with and without varying amounts of phosphorus (P) fertilizer on growth and yield of sunflower under field conditions. The PSB application was able to mobilize P efficiently in the sunflower and improved seed quality and oil yield. It also enhanced the head diameter, 1000 seed weight, kernel ratio and oil content and led to seed and oil yield increases of 15.0 and 24.7% over no application, respectively. However, when PSB was used in conjunction with P fertilizers, a much greater effect was observed. It was found that the highest seed yield of sunflower possible with 100 kg P₂O₅ ha^-1 fertilizer was achieved with about 50 kg P₂O₅ ha^-1 when used in conjunction with PSB. But the important effect of PSB on oil yield was noted at 100 kg P₂O₅ ha^-1, possibly indicating increased PSB activity in the rhizosphere following PSB application and consequently by enhanced P solubilization as evidenced by the higher levels of P content of seed.

Key words: Phosphate solubilization, Bacillus, sunflower.

Abbreviation

PSB, Phosphate solubilizing bacteria; PGPR, plant growth-promoting rhizobacteria.