Nitrogen fertilizer synergist and application thereof

The invention provides a nitrogen fertilizer synergist. Every 100 parts of the nitrogen fertilizer synergist is prepared from, by weight, 94-98 parts of biochar, 1.0-3 parts of a urease inhibitor and 1.0-3 parts of a nitrification inhibitor. The raw materials are put into a stirrer, full stirring and even mixing are performed, the mixed materials are subpackaged in bags, and then the nitrogen fertilizer synergist is obtained. The nitrogen fertilizer synergist is suitable for producing long-lasting nitrogen fertilizer by taking urea or ammonium nitrogen fertilizer as the raw materials and can be applied to various soil along with the urea or ammonium nitrogen fertilizer, effectively prolong the fertilizer efficiency period of the urea or ammonium nitrogen fertilizer to 100-120 days, significantly increase the utilization rate of fertilizer nutrients, improve the soil, condition plant growth, increase the crop yield and improve the crop quality.