NOVELTY - Preparation of nutshell biological coal-based slow-release fertilizer includes sun-drying Eucommia, crushing, inoculating with white rot fungus strain, fermenting with glucose nutrient solution, pressurizing, and drying to obtain humic acid-enriched fertilizer; ultrasonically cleaning nutshell, vacuum-drying, carbonizing, crushing, and sieving to obtain nutshell biological coal; adding distilled water with sugar and starch, heating, adding dicumyl peroxide, and crosslinking to obtain crosslinked sustained-release coating liquid; and mixing carbamide, coal, fertilizer and kaolin.    USE - Method for preparation of nutshell biological coal-based slow-release fertilizer (claimed).    ADVANTAGE - The method is environment-friendly and effectively utilizes resources. The fertilizer can automatically decompose in soil for up to 15-20 days which does not affect the nutrient release performance.    DETAILED DESCRIPTION - Preparation of nutshell biological coal-based slow-release fertilizer comprises (A) sun-drying 10-20 kg Eucommia for 3-5 days, crushing into 60-70 mesh powder, sieving, adding into fermenter, inoculating with white rot fungus strain, adding 50 wt.% glucose nutrient solution, sealed-fermenting to 28-38 degrees C for 30-40 days, transferring into autoclave, pressurizing to 100-105 kPa, placing into oven, and drying to 105-110 degrees C to obtain humic acid-enriched fertilizer; (B) ultrasonically cleaning 1-2 kg nutshell at power of 100-200 W and frequency of 25-35 kHz for 10-20 minutes, vacuum-drying, adding into carbonization furnace, carbonizing to 300-700 degrees C, crushing, and sieving through 40-50 mesh sieve to obtain nutshell biological coal; (C) pouring 100-200 mL distilled water into 500 mL beaker, adding 20-30 g sugar and 30-40 g starch, stirring with glass rod, transferring into oil bath, heating to 100-120 degrees C while stirring for 20-30 minutes until mixture becomes viscous melt, adding 3-5 g dicumyl peroxide as crosslinking agent, and crosslinking to obtain crosslinked sustained-release coating liquid; (D) adding 40-42 wt.% carbamide, 10-12 wt.% nutshell biological coal, 35-37 wt.% humic acid-enriched fertilizer and 9-15 wt.% kaolin into mixer, and stirring while spraying with crosslinked sustained-release coating liquid to obtain wet coating material; and (E) loading into hot air drum granulator, mixing at speed of 300-350 revolutions/minute and temperature of 70-120 degrees C, granulating for 30-40 minutes, sieving through 30-40 mesh steel sieve, and oven-drying to 105-110 degrees C.