Among other characteristics, both need basic nutrients to keep them going. Plants need three major and ten minor nutrients for healthy growth. Nitrate is the form most readily absorbed by plants and most desirable as a fertilizer. Leafy vegetables, such as spinach, cabbage, kale and lettuce, especially benefit from fertilizers with a high nitrogen content. Nitrogen-deficient plants display leaves that yellow from their tips toward the stem.
Excessive nitrogen creates weak spindly growth, resulting in few flowers and fruits.
Nitrogen can be lost in the soil by the leaching action of irrigation and rainfall. Phosphorus Phosphorus is important to early root growth, cell division and respiration. It's also necessary for fruit production. Phosphorus doesn't dissolve and move through the soil. The root tips absorb whatever phosphorus that is available, so it must be placed as near to the roots as possible to be accessible to the plant.