Oedjijono, Endang Sutariningsih Soetarto, Sukarti Moeljopawiro and Heru Adi Djatmiko
Iron sand soil of Purworejo Coast, Central Java, Indonesia isdominated by sand materials having low organic matters and contains 12.51% of iron. The objectives of the study were toobserve the occurence of Azospirillum spp.on iron sand and rhizosphere soils and to assess theirabilityin fixing atmospheric nitrogen, producing indole acetic acid, and solubilizing inorganic phosphates in vitro. The results showed that a hundred and eighteen strains of Azospirillum spp. were successfully isolated from iron sand and rhizosphere soils. The bacterial population on iron sand and rhizosphere soils were ranged from 0.01-6.0 x 105 CFU g-1and 0.04-8.0 x 107CFU g-1, respectivelly. Most of bacterial isolates were capable of fixing nitrogen ranging from 5.73-99.539 ppm, and higher abilities were shown by six isolates of HR11, HP51, KP11, KR13, KP35, and KR66. These six selected isolatesalso produced IAA and solubilized phosphates. Strain of HR11 showed the highest IAA production which was about58.84mg mL-1;and higher phosphate solubilization of Ca3(PO4)2 was shown by HR11 and KP35 isolates with E values of 140.74 and 133.13, while higher solubilization to FePO4 showed byKP11 and KR66 strains with E values of 140.60 and 127.22. Among all phosphorous substances, AlPO4 appeared to be the most difficult substance to be solubilized by the six bacterial tested
