MICROBIAL SOLUBILIZATION OF PHOSPHATE- POTASSIUM ROCKS AND THEIR EFFECT ON KHELLA (Ammi visnaga) GROWTH

Biofertilizers have been used as sources to improve plant nutrients in sustainable agriculture. Experiments were conducted to evaluate the potential of several phosphate solubilizing bacteria (PSB) Bacillus megaterium and potassium solubilizing bacteria (KSB) Bacillus circulans to solubilize tricalcium phosphate (TCP), rock phosphate (RP) and feldspar respectively in pure culture and field experiments to determine the effect of these bacteria on releasing P and K as well as their effect on Ammi visnaga (khella) growth. Seven strains of B. megaterium were selected on the basis of the clearance zone on solid agar media of Pikovskaya containing TCP. B. megaferium KL1, BF2 (showing the highest of solubilizing index) were tested to study their efficiency to dissolve phosphorus in liquid culture amended with TCP and rock phosphate individually, the latter strain was more effective in releasing phosphate from the two tested sources. Five Bacillus circulans strains were tested for their ability to solubilize feldspar in Afeksandrov s liquid medium. Their effectiveness ranged from 2.09 - 8.64 % and generally the pH decreased. Bacillus circulans F5 has the highest value of soluble potassium in the medium. A field experiment was conducted during two successive seasons 2006 I 2007 and 2007 I 2008 to determine the influence of : 1- Phosphate fertilizer namely: calcium superphosphate at the recommended dose (200 kg / fed.), rock phosphate at the rates of (128 256 kg / fed.) and biofertilization with Bacillus megaterium BF2 and their interactions. 2- Potassium fertilizer namely: potassium sulphate at the recommended dose (50 kg / fed.), feldspar at the rates of (240 480 kg / fed.) and biofertilization with B. circulans F5 and their interactions. The highest values of all parameters were observed when the plants received calcium superphosphate and / or rock phosphate at the high rate. In regard to biofertilizer treatments, all of them fed to a significantly increase in the growth criteria during the two successive seasons. The similar results were obtained in potassium treatment.