Fertilizer black inner additive, preparation method and application

The invention relates to a fertilizer black inner additive, a preparation method and application. The fertilizer black inner additive is composed of water, a dispersant and a pigment carbon black, and is prepared according to the following steps: adding weighed water into a reaction kettle and heating to 30-40 DEG C through vapor, weighing 0.1-0.2% of Tween-80, 0.2-0.3% of AEO9, 0.5-1.0% of sodium polyacrylate and 10-15% of the pigment carbon black according to the mass percentage, successively adding into the reaction kettle, and fully stirring for uniform mixing; grinding the uniformly-mixed solution by employing a grinding machine, controlling the rotation speed to be 1000 r/s and the grinding time to be 4-6 h, so as to fully disperse the solution and obtain the fertilizer black inner additive. The usage amount of the fertilizer black inner additive in per ton of a fertilizer is 0.2 Kg-1.0 Kg, and the fertilizer black inner additive performs black dyeing on the fertilizer, so that a corresponding black or ash-black fertilizer is obtained. The fertilizer black inner additive has the advantages of strong covering capability, stable properties, low cost, low usage amount, no public hazard and the like.