Inorganic and organic foliar fertilisation in olives

The application of nutrient solutions to the foliage of plants is an alternative means to fertilise crops. Foliar fertilisation is used to overcome the disadvantages of soil applications. Variable plant responses to these foliar fertilisation spray solutions have often been described in the literature. However, knowledge about the penetration mechanisms, the role of a leaf-applied inorganic or organic solution, and the results obtained by its application is still limited. The complex character of the factors determining the effects of sprays hinders the development of suitable foliar fertilisation strategies, applicable under variable local conditions and for various plant types. This review describes some basic factors involved in the penetration process of foliar sprays in olive (Olea europaea L.) trees. Chemistry, leaf penetration, and plant nutrition principles will be merged with the aim of clarifying the constraints, opportunities, and future perspectives of sprays to cure olive tree nutrient deficiencies and, hence, both increase the yield and improve the fruit quality.