Organic fertilizer amended with immobilized bacterial cells for extended shelf-life

One of the major constrains in the development of microbially-amended agricultural products is the incapability of upholding high microbial count in the commercial products and field soil. The efficiency of immobilization technique to retain high microbial population and extend the shelf-life in bio-organic fertilizer was corroborated in this study. Four Gram negative bacterial strains with beneficial traits such as phosphorus solubilization, indole acetic acid production, siderophore production and nitrogen fixation were immobilized in a modified alginate solution and incorporated with compost, organic fertilizer and mineral fertilizer. The bacterial count in compost and organic fertilizer (5:5:5) were 10(7) cfu/g and 10(6) cfu/g respectively after one year of shelf-life. Mineral fertilizer (15:15:15) and immobilized bacteria that were mixed in 1:50 ratio exhibited 10(5) cfu/g after 210 days. Pelleting was found to be more suitable for liquid bacterial cells + organic fertilizer mixture than immobilized bacterial cells + organic fertilizer mixture. Sterilization technique by autoclaving was proven to be more destructive in eliminating indigenous microbes and effective in retaining nutrient content and immobilized bacterial cells as compared to gamma irradiation technique. One part of immobilized bacterial cells was mixed to fifty parts of organic fertilizer to sustain at least 10(6) cfu/g for 348 days. Field study results exhibited the efficiency of immobilized bio-organic fertilizer in increasing cabbage head weight as compared to organic fertilizer. This is also a pioneer report on the shelf-life of immobilized bacterial cells incorporated with organic and mineral fertilizers.