NOVELTY - Carbon-based sustained-release fertilizer comprises humic acid raw powder, humus, amino acid chelated fertilizer granule, modified tapioca starch solution, rare earth element, rice straw, attapulgite, monoammonium phosphate, plant ash, and tea powder, where the modified tapioca starch solution comprises cassava starch, concentrated sulfuric acid, potassium permanganate solution, sodium hydroxide, borax, sodium selenite, calcium bicarbonate, and water.    USE - As carbon-based sustained-release fertilizer.    ADVANTAGE - The carbon-based sustained-release fertilizer is rich in nutrients, suitable for long-term usage and less labor intensive, rapidly exhibits fertilizing effects, and has excellent absorbability.    DETAILED DESCRIPTION - Carbon-based sustained-release fertilizer comprises 506 pts. wt. humic acid raw powder, 24-26 pts. wt. humus, 6-9 pts. wt. amino acid chelated fertilizer granule, 4-6 pts. wt. modified tapioca starch solution, 8-10 pts. wt. rare earth element, 17-19 pts. wt. rice straw, 4-6 pts. wt. attapulgite, 6-7 pts. wt. monoammonium phosphate, 30-35 pts. wt. plant ash, and 12-16 pts. wt. tea powder, where the modified tapioca starch solution 45-55 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 (remainder), and the modified tapioca starch solution is prepared by dissolving cassava starch in 2 times water, constantly stirring the mixture, adding concentrated sulfuric acid, stirring the mixture for 5-10 minutes, adding potassium permanganate solution, oxidizing the mixture for 50-70 minutes, constantly stirring the mixture, adding sodium hydroxide, gelatinizing the mixture for 15-25 minutes, adding borax, cross-linking the mixture for 10-20 minutes, adding sodium selenite, stirring the mixture, heating the mixture at 60 degrees C for 15 minutes, finally adding calcium bicarbonate, reacting the mixture at 90 degrees C, chelating the mixture for 30 minutes, adding 9 times water, stirring the mixture and diluting the mixture. An INDEPENDENT CLAIM is included for method for preparing the above-mentioned carbon-based sustained-release fertilizer.