Foliar Fertilizers – Are they effective?
There is a growing trend of spraying fertilizer on crops lately. Practitioners believe that foliar feeding is advantageous over soil application and it is linked with higher yields, and better fruit quality.
For those that are new to the practice, foliar feeding is the application of foliar sprays of one or more mineral nutrients to plants to supplement traditional soil application. It is not a new practice and in fact, Gris noted that this practice was first used as long ago as 1844. The practice is currently used widely in fruit and vegetable production.
Plants have the ability to absorb essential nutrient elements through their bark and leaves especially via the stomata and the epidermis. H.B. Tukey the (then) head of Horticulture department of Michigan State University (1950s), worked with S. H. Wittwer, and confirmed irrefutably that foliar feeding is effective. Radioactive phosphorus and potassium were applied to foliage and a Geiger counter was used to observe absorption, movement and nutrient utilization. The nutrients were transported at the rate of about one foot per hour to all parts of the plants.
In order for a foliar fertilizer nutrient to be utilized by the plant for growth, it must first gain entry into the leaf prior to entering the cytoplasm of a cell in the leaf. To achieve this, the nutrient must effectively penetrate the outer cuticle and the wall of the underlying epidermal cell. Once penetration has occurred, nutrient absorption by the cell is similar to absorption by the roots. Of all the components of the pathway of foliar-applied nutrients, the cuticle offers the greatest resistance.
Under certain conditions, foliar feeding becomes more advantageous over soil application. Under Nutrient deficiency, foliar feeding has been proven to offer faster and more efficient recovery. Foliar feeding is recommended especially when prevailing conditions hinder uptake of nutrients by roots. These could be environmental conditions such as too low or too high soil moisture, nutrient imbalances in soil, root diseases or presence of pests that affect the root system, high or low soil pH, temperature stress and many more.
Different plant growth stages require specific nutrients for optimal performance. Ensuring sufficient availability of these nutrients in their specific ratio compositions in the soil is sometimes difficult. Foliar application therefore of these essential nutrients during specific growth stages could be the only way of providing the necessary balance of nutrients in order to improve crop yield and produce quality.