What fertilizer will help plants grow best?

The best kind of fertilizer depends on the soil you have, what you are growing and what the climate is like. A good rule of thumb is to use organic fertilizer because it won't burn the plants, won't add to soil salinization and releases nutrients more slowly. Many types of organic fertilizer (e.g. fish emulsion, kelp, cottonseed meal and others) also add micronutrients to the soil, which adds to its long-term health.