Principles and Practices of Foliar Fertilization

Foliar fertilization is a widely used practice to improve the efficiency and rapidity of 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.  Indiscriminate application of foliar-applied nutrients without due consideration of soil availability and plant nutrient status can be wasteful.  A sound soil test as well as accurate tissue analysis is a fundamental requirement for a successful fertilization program. Foliar applications have the advantage of allowing producers to add the necessary nutrient when tissue analysis indicates a pending shortage, and thereby correct the deficiency and prevent yield loss.  The choice of the fertilizer formulation with particular respect to concentration is critical.  Phytotoxicity is of grave concern if the concentration is too high.  In addition, different formulations for any particular nutrient can behave very differently and thereby effect the efficiency of absorption.  When more than one agrochemical are applied together as is often done, possible incompatibility between  the chemical compounds could result in reduced efficacy of either chemical. Environmental conditions can seriously affect the absorption of a foliar-applied nutrient, particularly temperature, humidity and wind.  In general, foliar applications should be made either early morning or late evening for maximum absorption by the plant, and no foliar applications should be made to water-stressed plants.  Adjuvants can improve the efficiency of absorption of a foliar-applied nutrient by prolonging the time the nutrient remains in solution on the leaf surface and thereby improving the absorption efficiency.   More research is needed to determine the amounts of each specific nutrient that actually reaches the target (e.g the fruit to be harvested) and how much of the total budget of these organs this constitutes. Information is also needed on the quantification of environmental effects, humidity and temperature in particular, on the absorption of foliar-applied fertilizers.  In general there is a lot of conflicting information about the benefits of foliar fertilization, but 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.

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Derrick M. OosterhuisDistinguished Professorship of International Crop Physiology
University of Arkansas
oosterhu@uark.edu


Derrick M. Oosterhuis, Distinguished Professorship of International Crop Physiology in the Department of Crop, Soil and Environmental Science at the University of Arkansas.  He earned his B.S. at Natal University in South Africa, his M.S. at the University of Reading in England, and his Ph.D. at Utah State University.  Dr. Oosterhuis has over 30 years experience as an agronomist/physiologist and has lectured or worked in 15 countries, taught 10 different courses, and advised 30 graduate students.  He has published over 900 scientific articles including 2 books, 20 book chapters, and edited 20 proceedings.  His research focuses on stress physiology, plant nutrition, foliar fertilization, drought tolerance, and plant growth regulation.  He was selected as the Outstanding Cotton Physiologist at the Beltwide meetings in 2000.  He is chair of the Arkansas Cotton Research Group, advisor to cotton boards in three countries, a member of two UN/FAO committees on growth regulators and nutrition, and a “fellow” in the American Society of Agronomy and also in the Crop Science Society of America.