Inoculation of sugar mill by-products compost with N2-fixing bacteria

Inoculation of sugar mill by-products compost with N2-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter vinelandii(ATCC 478), Beijerinckia derxii (ATCC 49361), and Azospirillumsp. TS8, each alone and all three together. Numbers of all N2-fixing bacteria in compost declined from an initial population of 5 × 105 cells g−1 during incubation. The population of Azotobacter declined to approximately 2 × 102 cells g−1 and the population of Beijerinckia and Azospirillum declined to approximately 9 × 103 and 3.5 × 104 cells g−1 respectively, at day 50. Inoculation with N2-fixing bacteria increased acetylene reduction, total N by 6–16 and available P by 25–30% in comparison to the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefit from providing N2 fixing bacteria.