The Difference Between Plant Food & Fertilizer

Is basically building blocks (basic elements) which can be compared to "raw materials" used in the photosynthesis process to create energy (carbohydrates = fructose = plant sugars), and then is dissolved in water in the soil and carried through the roots up to the leaves of the plants.

Plants utilize the sugars (plant energy) to create starch. The starch is used to create new stems, leaves, flowers, etc. But without fertilizer, an important component of the photosynthesis process could not be carried out (the production of sugars and starches). In the extreme example that NO fertilizer is available the plant would shows signs of "nutrient deficiency" and eventually die as no food would be produced. The plant can not produce plant food (sugars) without fertilizer even if water, carbondioxide and sunshine was available. However, for plants which develop bulbs and other enlarged storage units (such as potatos, onions, etc) you have to look at the effect of fertilizer over a longer period.

If fertilizer is lacking, or not available in sufficient quantities, to replentish the withdrawn energy (what borrowed from the bank) the bulb will eventually shrink and in the end the plant will die.

For example, Miracle Grow 15-30-15 All Purpose Water Soluble Plant food contain these nutrients (lable):

Nitrogen: 15%

Available Phosphate (P2O5) 30%

Soluble Potash (K2O) 15%

Boron (B) 0.02%

Copper (CU) 0.07%

Iron (FE) 0.15%

Manganese (MN) 0.05%

Molybdenum (MO) 0.0005%

Zinc (Z) 0.06%

EDTA (Chelating Agent) 1.14%

The mixture is put together in the volumes by which plants normally take up the nutrients. For example, plants take up substantial quantities of nitrogen, potash, and potassium but very small amounts of Iron, Zinc and Boron for example (in fact these can be lethal to plants in larger amounts).

You should know that plants respond differently to different compounds. For example, fertilizers with high levels of nitrogen promotes green, leafy growth (e.g. nitrogen is high in lawn fertilizers) but too much can prevent fruiting or flowering. Example 29-3-4.

Fertilizers high in potassium and/or phosphorous (compared to nitrogen) tend to be used for flowering and fruiting plants as these plants consume large amounts of these nutrients. Example 5-10-10, 15-30-15, etc.

Plants need all 16 essential nutrients to grow. If just one is missing, the plant will die. However, some nutrients (as outlined above) is needed in very small quantities (and some nutrients will almost always be readily available, such as sulfur). Others are depleted fast from the soil and must be supplied often (nitrogen, potassium).

Generally, if a given soil is deficient in the nutrient being applied, plants respond dramatically to being fertilized. If the soil has adequate amounts of fertilizer, response will generally be modest or none.