Foliar Nutrition of Protected Crops
Keywords: Foliar nutrition, Protected crops, Macronutrients, Micronutrients.
Some theoretical advantages and limitations of using foliar nutrition on protected crops are reviewed and discussed related to three categories for the use of foliar fertiliser application:
1. Use to overcome a soil deficiency of a microelement.
2. Use to supplement a low level of soil fertilisation by foliar application of one or more macroelements.
3. Use to potentially increase the yield of crops which have received adequate nutrients by soil fertilisation and do not show deficiency symptoms.
The main conclusion is that batch applications of foliar micro- or macro- nutrients, alone or in combination, will nearly always be a less effective option than application of nutrients to the soil for uptake by the root. In protected crop environments efforts should first be made to provide a suitable soil substrate for the roots with addition of fertilizers to correct deficiencies or flushing the soil substrate with water in order to remove excessive salts. Similarly, occurrences of biotic stress which inhibit nutrient uptake should be minimized or corrected by chemical means. Foliar nutrition can provide a convenient alternative for providing nutrients to the plant if root problems persist, or, if a specific benefit of foliar nutrition has been unequivocally established for a particular crop.