Garden soils do not have all the minerals required for plant growth year after year. Potting mixes contain few essential minerals for plants and are sterilized and so may lack microbes to break down organic matter. Within months plants have used the available supply. Mineral nutrients must be applied, in the field or the container. Dyna-Gro is more than a fertilizer.
Ordinary fertilizers are incomplete.
Incomplete mixes require buying different fertilizers to meet plant needs. The Elements of Complete Plant Nutrition Complete nutrition rewards with superior plant growth. There are 20 elements necessary for plant growth. Air and water supply carbon, hydrogen, and oxygen. Six macronutrients are required by plants in large amounts.