Principles of Foliar Nitrogen Fertilization of Cotton.

Foliar fertilization is a widely used practice to improve the efficiency and utilization of a nutrient urgently required by the plant for maximum growth and yield.  However, there are still many misconceptions about the practice and methods of application that result in poor efficiency and reduced economic returns.  Foliar fertilization should only serve as a supplement to traditional soil-applied fertilizer.  However, when deficiencies occur, foliar fertilization provides an efficient means of rectifying the problem and ensuring optimal growth and yields. This paper will review the principles underlying successful foliar fertilization, including the fundamental need for an initial soil test followed by tissue analysis, the importance of fertilizer formulation, possible phyotoxicity, caution about incompatibility when combining agrochemicals in foliar applications, the effect of plant water status, the optimum diurnal time of application, the effect of environmental conditions on nutrient absorption, the use of adjuvants, and the dynamic nature and role of the leaf cuticle in nutrient absorption.  Although there is conflicting information about the benefits of foliar fertilization, the scientific evidence to date and the widespread practical use of this phenomenon indicate that it is a viable and useful practice for improved crop production. A sound knowledge of the fundamentals involved in foliar fertilization will ensure a higher efficiency and enhanced economic returns.