NOVELTY - Slow release biofertilizer comprises microbial agent composition, inorganic fertilizer and humic acid. The microbial agent comprises microbial bacteria in culture medium, where the microbial bacteria comprises Bacillus laterosporus, Bacillus megaterium and nitrogen-fixing Paenibacillus, the culture medium comprises organic powder and inorganic fertilizer. The organic powder is e.g. meadow soil. The inorganic fertilizer contains urea, monoammonium phosphate, potassium chloride, borax, copper sulfate and manure.    USE - The slow release biofertilizer is useful for tubers (claimed) for preventing and treating antagonistic strains of soil borne diseases.    ADVANTAGE - The slow release biofertilizer is environmentally-friendly, rich in nutrients. The fertilizer is prepared by simple and cost-effective method.    DETAILED DESCRIPTION - Slow release biofertilizer comprises 10-40 pts. wt. microbial agent, 50-80 pts. wt. inorganic fertilizer and 8-10 pts. wt. humic acid. The microbial agent composition comprises 106 cells/g in culture medium. The microbial bacteria comprise 40-60 pts. wt. Bacillus laterosporus (ACCC 11079), 20-30 pts. wt. Bacillus megaterium (ACCC100011) and 20-30 pts. wt. nitrogen-fixing Paenibacillus (ATCC35681), the culture medium comprises 80-90 pts. wt. organic powder, and 10-20 pts. wt. inorganic powder. The organic powder is at least three chosen from meadow soil, wheat bran, rice bran, soybean, cypress, corn core powder, peanut shell powder, straw powder and cotton seed hulls. The inorganic fertilizer is chosen from 10-50 pts. wt. urea, 5-20 pts. wt. monoammonium phosphate, 5-30 pts. wt. potassium chloride, 0-1 pt. wt. borax, 0-1 pt. wt. magnesium sulfate, 0-1 pt. wt. copper sulfate, 10-30 pts. wt. humic acid and 10-30 pts. wt. manure, where the urea is urea with 46.2 %mass nitrogen content of particle diameter 0.85-2.8 mm, monoammonium phosphate is common powder with nitrogen content of 11 wt.% and phosphorus pentoxide content of 44 %mass, potassium chloride is white powder with potassium oxide content of 60 %mass, molecular weight of brownish black humic acid powder is 2000-5000 whose dry basis humic acid content is not less than 45 %mass, except urea granules the grain diameter of remaining raw materials are not greater than 1 mm. An INDEPENDENT CLAIM is included for method for preparing the fertilizer which involves (a) (i) taking 3-8 times B.laterosporus spores with respect to the total weight of microbial agent composition, mixing and stirring to obtain granular B.laterosporus, (ii) taking 3-8 times B.megaterium spores with respect to the total weight of microbial agent composition, mixing with adsorbent and stirring to obtain granular B.megaterium and (iii) taking 3-8 times nitrogen-fixing Paenibacillus spores with respect to the total weight of microbial agent composition, mixing with adsorbent and stirring to obtain granular nitrogen-fixing Paenibacillus, (b) (i) melting urea at 125-135 degrees C, (ii) mixing monoammonium phosphate, potassium chloride, borax, magnesium sulfate, copper sulfate, humic acid and manure in mixing tank in suitable proportion, crushing the mixed raw material using crusher and then feeding into drum granulator, passing steam through the steam nozzle into granulation drum, simultaneously injecting the melted urea into the granulation drum, heated the material at 40-50 degrees C and (iii) drying using hot air, cooling, screening and packing and (c) mixing suitable proportion of microbial agent composition, inorganic fertilizer and humic acid and stirring product.