Two field experiments were carried out at Sids Agricultural Re‌search Station, during 1996 and 1997 seasons, to study the effect of two planting dates (March, 15th and April, 15th) and three levels of po‌tassium fertilizer (0,24 and 48 kg K20/fed) on yield components, and quality of fiber and seed. The resuls revealed that early planting increased number of fruit‌ing branches/plant, nuumber of total and open bolls/plant, seed cotton yield, fiber fineness and fiber strength, but it decreased plant height and position of first fruiting node and earliness percentage. On the other hand, it had no effect on boll weight, seed index, lint percentage, oil and protein percentages in cotton seeds. Potassium application increased number of fruiting branches/ plant, number of total and open bolls/plant, boll weight, seed cotton yield, earliness percentage, lint percentage, seed index, micronaire read‌ing, Pressley index, oil and protein percentages, while it deceased the position of first fruiting node. The level of 24 kg K20/fed., is considered to be suitable amount for cotton production under the conditions of the experiment. The interaction did not exert any significant effect on all characters under study.