In addition to nitrogen, phosphorus, and potassium, the main components of compound fertilizer also include fillers.
Specifically:
Filler: In addition to the three main nutrients of nitrogen, phosphorus, and potassium, the remaining part of compound fertilizer is mainly composed of filler. These fillers are not considered as effective nutrients according to the requirements of GB150632001 national standard. The main function of filling material is to increase the volume of fertilizer, facilitate storage, transportation, and use, and also contribute to the uniform dispersion and application of fertilizer.
It should be noted that the composition and proportion of the filling material may vary among different brands and types of compound fertilizers. But overall, fillers in compound fertilizers mainly serve as auxiliary and carrier functions, rather than providing nutritional elements.
