Nitrogen fertilizer urea, ammonia sulfate, ammonia bicarbonate, ammonium chloride and other fertilizers all appear white crystals, can be identified by the following methods. (1) Ignition method: decomposition of ammonium nitrogen occurs when it is heated. Therefore, a small amount of fertilizer can be placed on the iron plate and burned on the flame. If there is a strong irritating odor and no residue is left, the nitrogen fertilizer is of high purity; if there are more residues, it means that the nitrogen content is low. (2) Dissolution method: Ammonium nitrogen can be dissolved in water. A small amount of chemical fertilizer can be used and a small amount of water can be added. If all of them are dissolved, the nitrogen fertilizer content is of high purity. If there is partial or total insolubility, it contains more impurities. (3) Add slaked ash mixing method: mix a small amount of chemical fertilizer with slaked lime, stir, and immediately smell the thicker nitrogen fertilizer odor, indicating that the nitrogen content is high. (4) Color reaction method: Ammonium bicarbonate and ammonium carbonate are alkaline. You can use red radish skin (or red amaranth) to boil, take clear solution, and put a small amount of ammonium bicarbonate into the serum if the carrot skin is used. Changing from purple to light green (or red amaranth juice from red to yellowish green) is pure. Phosphate calcium superphosphate should be gray, granular, acidic, and partially soluble. Take calcium phosphate to add a small amount of water, if there is partial dissolution, it can be preliminarily determined that it is superphosphate. The above red radish skin juice (or red amaranth juice) was used to examine if the solution changed from purple to bright red (or red amaranth juice changed from red to dark red), indicating that the quality of superphosphate was good. China Agricultural Network Editor