Special coloring agent of diammonium phosphate compound fertilizer and preparation method thereof

The invention discloses a special coloring agent of a diammonium phosphate compound fertilizer, comprising the following constituents: 40-50 parts of humic acid salt, 0.1-3 parts of carbon soot, 2-4 parts of acid black, 1-2 parts of acid brilliant scarlet, 0.2-1 part of sodium hexametaphosphate, and 40-56.7 parts of water by weight parts; the preparation process is that: the material is prepared by weight parts, water is added in a vertical round reaction tank, and then the humic acid salt, the carbon soot, the acid black and the acid brilliant scarlet are added and are stirred uniformly, andthen sodium hexametaphosphate is added, the mixture is stirred continuously and uniformly, so as to obtain the special coloring agent of the diammonium phosphate compound fertilizer; the invention solves the problems that the diammonium phosphate particles produced under an acid slurry condition are easy to decolorize and the chromaticity is unstable; the special coloring agent of the diammonium phosphate compound fertilizer is green and environmental-protection, has no pollution and is beneficial to the growth of crops; the product is in a liquid state and transported closely, and has convenient usage; the raw material is cheap and easy to obtain, the cost is low and the economic benefit is good.