NOVELTY - Carbon based slow release nitrogen fertilizer is prepared by mixing 95-100 pts. wt. nitrogen loaded biochar, 1-5 pts. wt. attapulgite and 2-3 pts. wt. calcium lignosulphonate, stirring mixture, drying and pelleting the mixture to obtain product.    USE - The method is useful for preparing carbon based slow release nitrogen fertilizer used in vegetable field (claimed).    ADVANTAGE - The carbon based slow release nitrogen fertilizer has positive beneficial effects that the nitrogen nutrient release duration is prolonged, and coupling between nutrient release and crop demands is high, such that leaching loss of nitrogen nutrients is lower, and the fertilizer utilization rate is improved. The slow release nitrogen fertilizer improves physical and chemical properties of soil of vegetable fields, and increases organic matter of soils and the cation exchange capacity and granular structure of soil, prevents the soil from hardening, and improves hydrothermal condition of soil. The raw materials used in the fertilizer is cost-effective, and easily available, thus the slow release nitrogen fertilizer is low in production cost, and beneficial to realizing the ecological high-valued utilization of agricultural wastes.    DETAILED DESCRIPTION - Carbon based slow release nitrogen fertilizer is prepared by mixing 95-100 pts. wt. nitrogen loaded biochar, 1-5 pts. wt. attapulgite and 2-3 pts. wt. calcium lignosulphonate, stirring the mixture, drying and pelleting the mixture to obtain product. The nitrogen loaded biochar is prepared by (a) (i) selecting peanut shell for preparing biochar in anaerobic environment at 250-350 degrees C, crushing biochar to 1-2 mm size, soaking the crushed biochar in water for 8-10 hours, washing with clean water for 2-3 times to remove ash and impurities, and drying the biochar, and (ii) adding 10-25% nitrogen to biochar in weight ratio of 1:8-12, shaking mixture for 10-24 hours, filtering the mixture, and drying the mixture to obtain nitrogen loaded biochar, and (b) treating attapulgite to 60-80 KHz ultrasonic irradiation for 1-3 minutes, and crushing the attapulgit to 200-300 mesh size. An INDEPENDENT CLAIM is included for preparation of the fertilizer, which involves (a) performing above-mentioned method (a) (i), (b) performing above-mentioned method (a) (ii), (c) treating attapulgite to 60-80 KHz ultrasonic irradiation for 1-3 minutes, and crushing the attapulgit to 200-300 mesh size, and (d) mixing 95-100 pts. wt. nitrogen loaded biochar, 1-5 pts. wt. attapulgite and 2-3 pts. wt. calcium lignosulphonate, stirring the mixture, drying and pelleting the mixture to obtain product.