Myth: Fertilizers are plant food.
Truth: Plants produce their own food.
Plants are autothrops, which means they are self -feeding. They produce their own food. While humans and animals consume other living organisms to survive, plants photosynthesize. Plants contain chlorophyll that allows them to capture solar energy needed to convert carbon dioxide and water into sugars, carbohydrates and proteins that are necessary food for all organisms.
If fertilizers are not plant food then what are they?
Fertilizers are materials that contain one or more of the essential elements used as soil amendment. Fertilizers can be applied to the soil or by foliar application, i.e. spraying to the leaves. The essential elements become integral components of the food manufactured through photosynthesis. Without one or more of the essential elements, the plants will not be able to complete their growth cycle. That is the reason that they are called "essential" elements.
Plant nutrition - refers to the plant’s need for and use of the essential elements for growth and development. The essential elements are also referred to as nutrient elements.
Availability of these elements in the soil depends on soil fertility, which is the inherent capacity of the soil to supply nutrients to plants in adequate amounts and suitable proportions. The soil naturally contains all these elements but the condition of the soil determines whether such elements are in available or bound in form. To give you very simple example, nitrogen can be present in the soil but when soil moisture is limiting, nitrogen cannot be absorbed by plants. Then there is soil chemistry that determines how these elements are attached to each other. Soil acidity, better known as soil pH, plays an important role is the availability of a number of the micro nutrients in the soil. When the availability of these elements is limited in the soil, fertilization becomes necessary. Fertilization is the application of nutrient elements to the environment around a plant to meet its nutritional need.