Earlier-maturing, faster-fruiting, higher-yielding, modern cotton varieties have a relatively high need for potassium in a relatively short period from flower initiation to boll maturation. During this peak demand, the limited root system is not capable of absorbing the required amount of potassium for boll development, not even in soils well-fed with potassium. Foliar-applied K, as with potassium nitrate, offers the opportunity of correcting K-deficiency more quickly and efficiently.
Oosterhuis, D., K. Hake and C. Burmester. 1991. Foliar feeding cotton. Physiology Today (2): 1-8.