From Agronomists of the
Potash & Phosphate Institute
655 Engineering Drive, Suite 110
Norcross, Georgia 30092-2837
Phone (770) 447-0335

Spring 1997, No. 6


Much is known about potassium nutrition of cotton...but not enough to give growers and crop advisers the confidence that soil test results and applied fertilizer will always provide the crop with its needs at vital growth stages for optimum yield, quality and profitability.

Potassium nutrition and fertilizer management were prominent topics of discussion by researchers, crop advisers and growers during the 1997 Beltwide Cotton Conference. Many were seeking the answer(s) to the question of why late season potassium deficiency symptoms are developing in today's high yielding cotton. Specialists believe that no single reason covers all fields and regions. Instead, it might be due to any one or more of the following.

What can be done? University of Georgia cotton specialists suggest that a good line of defense is to understand cotton nutrient needs by growth stage, soil test, and then fertilize with potassium in a balanced nutrition program. In addition, a split application of potassium and other needed mobile nutrients can help to minimize the effect of nutrient loss by leaching from sandy, low cation exchange capacity soils in high rainfall regions. A third consideration is to use leaf and petiole analysis to monitor nutrient status in the crop during the critical periods of first flower and early boll development. When late season shortages are detected or strongly suspected, a foliar application of potassium, boron and nitrogen can be helpful. Foliar fertilization during early boll development seems to fit best under conditions of heavy boll set, limited crop stress, and adequate heat units for boll development. Scientists suggest the use of an adjuvant and the adjustment of the foliar solution to a pH between 4 and 6 for improved nutrient absorption by cotton leaves. The primary objective of maintaining a fertile soil and a sound fertilization program is to remove nutrition as a limiting factor for cotton production. Research continues to document that healthy plants can better tolerate the stress brought on by drought, insect-disease injury, or temperature extremes.


For more information, contact Dr. Noble R. Usherwood, Southeast Director, PPI, 655 Engineering Drive, Suite 110, Norcross, GA 30092-2837. Phone (770) 825-8070.
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