NOVELTY - Slow-release fertilizer comprises attapulgite, urea, chicken manure, raw humic acid powder, modified cassava starch solution, ammonium chloride, zinc sulfate, biogas, rice straw and rice bran. The modified cassava starch solution comprises cassava starch, concentrated sulfuric acid, potassium permanganate solution, sodium hydroxide, borax, sodium selenite, calcium bicarbonate and water.    USE - As nitrogen-rich carbon-based slow-release fertilizer (claimed).    ADVANTAGE - The nitrogen-rich carbon-based slow-release fertilizer satisfies nutrient needed for crops and improve soil ability to fix nitrogen and reduces nitrogen loss.    DETAILED DESCRIPTION - Slow-release fertilizer comprises 8-10 pts. wt. attapulgite, 6-9 pts. wt. urea, 24-28 pts. wt. chicken manure, 5-7 pts. wt. raw humic acid powder, 4-6 pts. wt. modified cassava starch solution, 4-7 pts. wt. ammonium chloride, 1-2 pts. wt. zinc sulfate, 20-24 pts. wt. biogas, 14-16 pts. wt. rice straw and 18-22 pts. wt. rice bran. The modified cassava starch solution comprises 45-52 pts. wt. cassava starch, 2-3 pts. wt. concentrated sulfuric acid, 4-6 pts. wt. potassium permanganate solution, 3-5 pts. wt. sodium hydroxide, 1-2 pts. wt. borax, 2-3 pts. wt. sodium selenite, 2-4 pts. wt. calcium bicarbonate and water. The modified cassava starch solution is prepared by dissolving cassava starch twice in water, adding concentrated sulfuric acid and stirring constantly and catalysis for 5-10 minutes, adding potassium permanganate solution and oxidizing for 50-70 minutes and stirring constantly, adding sodium hydroxide and gelatinizing for15-25 minutes, adding borax and cross-linking for 10-20 minutes, stirring and adding sodium selenite to water, heating and above reaction at 60 degrees C and chelating for 15 minutes, stirring and finally adding calcium bicarbonate to water, heating at 90 degrees C and chelating for 30 minutes, adding 9 times water and diluting the resulting solution, stirring uniformly and cooling to obtain product. An INDEPENDENT CLAIM is included for method for preparing slow-release fertilizer, which involves (a) mixing chicken manure, biogas and rice bran, adding 40-50% water and composting mixture for 25-28 days, (b) drying composed mixture, adding urea, ammonium chloride and zinc sulfate to dried materials, crushing mixture, mixing uniformly, and granulating the mixture using machine, (c) performing pyrolysis for rice straw at 550-650 degrees C for 2-3 hours to obtain biomass charcoal powder, and (d) mixing biomass charcoal powder obtained in step (c), raw humic acid powder, attapulgite and 60% modified tapioca starch solution and stirring uniformly, mixing remaining humic acid powder and granules in a rolling machine for 40-50 minutes, heating roller at 80-100 degrees C and spraying remaining 40% modified cassava starch solution to roller for 50-70 minutes, filtering and sieving using 20 meshes, to obtain product.