Foliar Fertilization with Potassium: Principles and Practices
Derrick M. Oosterhuis
Department of Crop, Soil, and Environmental Sciences,
University of Arkansas, Fayetteville, AR 72701
    oosterhu@uark.edu
    Abstract
The advent of widespread K deficiency across the US Cotton Belt has focused attention on K fertilization and plant monitoring of K status in cotton production systems.  However, the yield response to foliar-applied K fertilizer has been inconsistent. Part of the reason for this is associated with the lack of understanding of the fundamentals needed for successful foliar fertilization.  While there are many reports on research involving soil-applied K and the functions of K in the plant, there are relatively few on foliar-applied K.  The objective of this paper is to review the fundamentals of foliar-fertilization with K.  Generally, the efficiency of foliar fertilization can be influenced by the type of fertilizer, concentration and pH of the solution, the use of adjuvants, and compatibility with other agrochemicals.  Attention also needs to be given to the ideal method and timing for incorporation of foliar fertilization into existing production practices.  Variable yield responses to foliar fertilization are probably associated with incorrect timing of applications, the use of inappropriate fertilizer materials, and insufficient attention to soil available nutrients, the size of the boll load, and environmental conditions.  Overall, foliar fertilization has the advantages of low cost and a quick plant response, and it is particularly important when soil problems occur and root growth is inadequate.  On the other hand, it has disadvantages of possible foliar burn, solubility problems, and only a small amount of the nutrient can be applied at any one time.