Data on agronomic characteristics and technological properties of cotton fiber obtained during six years in ten field experiments where the effects of parcelling potassium application are discussed. Potassium fertilizer was applied at planting in furrows at the rates of 0, 60 and 120kg/ha of K2O in the form of potassium chloride highest, rate being parcelled by providing 1/3, 1/2, 2/3 as side-dressing, together with nitrogenous fertilizer and lightly incorporated by bringing soil to the plants. The experiments were grouped according to the results obtained by linear correlation between relative production and the analytic index of soil the most related to plants responses to potassic fertilization. In the group of high expected response to the fertilizer, significant effects of potassic fertilization were observed on Micronaire, maturity of the fibers and on the average weight of 100 seeds and of bolls. The parcelling of application increased significantly the values of uniformity of length of fibers and, in general, contributed to improve the average values of all the other charactristics studied. The effect of potassium was significant, furthermore, for weight of boll in the group of medium to low expected response to fertilization. The results obtained allow to emphasize the recent recommendation that application of high doses of potassium chloride to cotton should be parcelled, about 1/2 to 2/3 of total K2O being provided at the planting furrow and the remainder by side-dressing, specially when there is deficiency of potassium in the soil.