Proper plant nutrition for optimal crop productivity in cotton requires that nutrient deficiencies be avoided. However, nutrient deficiencies often occur for a variety of reasons, and can be rectified by timely application of the deficient nutrient. This usually entails some sort of soil application but after canopy closure, foliar application may be more appropriate. Foliar fertilization is a widely used method used to supplement soil applications to improve the yield and quality of cotton. Foliar fertilization can be used to improve the efficiency and rapidity of utilization of a nutrient urgently required by the plant for maximum growth and yield. However, concerns still remain about the value of this practice, in particular in relation to the amount of nutrient absorbed by the plant and the conditions that affect the efficiency of absorption. This presentation will describe foliar fertilization with nitrogen, the mechanism of nutrient uptake, the conditions that influence absorption, and precautions to ensure efficient absorption. In addition the nature and role of the leaf cuticle will be described.