Inoculation of Grass-cyclingcompost with N2-Fixing Bacteria

Inoculation of grass-cyclingcompost with N2-fixing bacteria may improve its quality by increasing total N and available P. Compost was inoculated with Azotobacter,Burkholderia and Azospirillum sp. each alone and all three together. Numbers of all N2-fixing bacteria in compost declined from an initial population of (5 x 105 cells/ g) during incubation. The population of Azotobacter declined to approximately (2 x 102cells/g) and the population of Burkholderia and Azospirillum declined to approximately (9 x103 and 4x 104 cells/ g) respectively, at day 40. Inoculation with N2-fixing bacteria increased acetylene reduction, total N by 5–15% and available P by 20–30% in comparison with the uninoculated control. Increasing the N content and P availability of compost increases its value and there may be additional benefits from providing N2-fixing bacteria.