NOVELTY - Organic-inorganic fertilizer composition comprises fertilizers, biological agent, ammonium humate, guar gum, magnesium sulfate, rare-earth metal complex, potassium polyacrylate, calcium sulfate, and sodium silicate. The biological agent contains Bacillus subtilis, B.megaterium, Nocardia, white-rot fungus, Agrobacterium, Rhizopus, Pseudomonas fluorescens, phosphate solubilizing bacteria, Rhizobium, and potassium solubilizing bacteria. The rare-earth metal complex comprises lanthanum oxide and cobalt oxide.    USE - As organic-inorganic fertilizer composition.    ADVANTAGE - The organic-inorganic fertilizer composition provides prolonged fertilization effect up to 15-25 days as compared to existing fertilizers, has high rate of fertilization efficiency and reduced production cost, increases usage rate of fertilizers, reduces usage amount of fertilizer, and is convenient to use.    DETAILED DESCRIPTION - Organic-inorganic fertilizer composition comprises 100-1000 pts. wt. fertilizers, 5-8 pts. wt. biological agent, 90-100 pts. wt. ammonium humate, 1-10 pts. wt. guar gum, 1-10 pts. wt. magnesium sulfate, 5-20 pts. wt. rare-earth metal complex, 5-8 pts. wt. potassium polyacrylate, 1-20 pts. wt. calcium sulfate, and 5-10 pts. wt. sodium silicate. The biological agent comprises Bacillus subtilis, B.megaterium, single cell bacteria, Streptomyces sp., Candida tropicalis, Nocardia, white-rot fungus, Vibrio parahaemolyticus, Klebsiella pneumoniae, Chaetomium thermophilum, nitrogen-fixing bacteria, Agrobacterium, Rhizopus, lactic acid bacteria, bacteria belonging to family Micromonosporaceae, Pseudomonas fluorescens, phosphate solubilizing bacteria, Rhizobium, and potassium solubilizing bacteria, where viable count of the above-mentioned beneficial microorganisms is 2 billion/g or more. The rare-earth metal complex comprises lanthanum oxide and cobalt oxide. An INDEPENDENT CLAIM is included for preparation method of the above-mentioned organic-inorganic fertilizer composition, which involves (a) taking fertilizers, ammonium humate, magnesium sulfate, rare-earth metal complex, calcium sulfate, and sodium silicate in the above-mentioned weight proportions, sieving the above-mentioned raw materials through sieve of 10 mesh size, adding sieved raw materials to biological agent, and stirring mixture uniformly, (b) preparing 10 %mass guar gum solution and 15 %mass potassium polyacrylate solution, and mixing both the solutions to obtain mixed solution, and (c) spraying the mixed solution uniformly on the mixture obtained in the step (a), and stirring the mixture uniformly.