The absorption takes place through their stomata and their epidermis. Transport is usually faster through the stomata, but total absorption may be as great through the epidermis. Plants are also able to absorb nutrients through their bark. The purpose of foliar feeding is not to replace soil fertilization. Supplying a plant’s major nutrient needs (nitrogen, phosphorus, and potassium) is the most effective and economic via soil application. However, a foliar application has proven to be an excellent method of supplying plant requirements for secondary nutrients (calcium, magnesium, and sulfur) and micronutrients (zinc, manganese, iron, copper, boron, and molybdenum), while supplementing N-P-K needs for short or critical growth three-stage periods. However, a foliar application has been shown to avoid the problem of leaching-out in soils and prompts a quick reaction in the plant. For all landscape and garden plants, the major pathway for nutrient uptake is by way of the roots. Leaves have a waxy cuticle, which restricts the entry of water, nutrients, and other substances into the plant. To a limited extent, nutrients applied to leaves can be absorbed and used by the plant, but for the major nutrients (nitrogen, phosphorus, and potassium) the quantity absorbed at any one time is small relative to plant needs. That means that foliar application of these three nutrients can only supply a tiny fraction of the total needed by the plant, so a foliar application should be considered a supplement to regular soil application of these nutrients.
Foliar Pesticide Application
Fruit trees can be treated by foliar application for an infestation of spider mites during the summer. Consider horticultural oil, which is an organic acaricide. It is always a good idea to aim to use chemicals as little as possible unless necessary. Look for biological and mechanical controls when available.
Foliar Application Tips
Foliar feeding is generally done in the early morning or late evening, preferably at temperatures below 75 degrees Fahrenheit (24 degrees Celsius), since heat causes the pores on some species’ leaves to close.
