Potassium deficiency developing late in the plant cycle has been observed in some cotton fields in Brazil and abroad. Experiments were conducted during 2 years to study the effects of timing and rates of foliar fertilization with KNO3 on cotton (Gossypium hirsutum L.) nutrition, yields and fiber quality in sites with different yield potentials. The experiments were developed in Pederneiras and Boracéia, SP, in the seasons 2000/2001 and 2001/2002. In the first two experiments 16 or 32 kg ha-1 of KNO3 were split in two or four times starting at the first week of flowering. In the other experiment 32 kg ha-1 of KNO3 were split in four times from the second to the fifth week of flowering. The decrease observed in K contents of cotton leaves was considered a natural process and was not reversed by K application. Foliar fertilization with KNO3 could, in some conditions, as in cotton plants deficient in K, increase the K contents in the leaves. However, this did not affect K contents in the cotton fruits, cotton yields and fiber quality.
Fiber quality; Gossypium hirsutum; Potassium nutrition
