The experiment was laid out in a split plot design with 3 replications having unit plot size of 5m 2 (2.5m ×2.0 m). Varieties were: BRRI dhan39, BRRI dhan40, BRRI dhan41 accommodated in the main plot and split application of potassium fertilizer (muriate of potash) was placed in the sub plot. Total number of plot was 36. The layout was done on 20 July having 1 m and 75 cm spacing between replications and the unit plots, respectively. Land preparation involved ploughing, harrowing and leveling in the field to make it suitable for crop establishment by a four wheel tractor. Soil was flooded and irrigated once with sufficient water to bring the top soil saturation and create an overlying water layer. The water depth was 5 cm but 10 cm was maintained for about one week after transplanting. From 30 days before head formation and flowering to the start of maturity, soil was frequently covered with water to a depth of 8 or 10 cm. A continual flow of water was maintained. The field was drained completely 30 to 45 days before harvest to ensure that the field would be dry enough for harvest. The source of K was commercially produced Muriate of Potash. Urea, Triple super phosphate, gypsum and zinc sulphate was applied at 120,100, 60 and 10 kg ha -1 respectively during final land preparation. Thirty days old seedlings were transplanted from a nursery bed to the main field maintaining 3 seedlings hill -1 with a spacing of 20 cm×15 cm. Necessary intercultural operations such as weeding, irrigation, pest management etc were performed accordingly and whenever needed to ensure the growth of a successful crop. Ten hills plot -1 were randomly uprooted before harvesting in order to collect the following **data** : Total number of tillers hill -1, number of effective tillers hill -1 , panicle length, number of grain panicle -1, number of unfilled spikelets panicle -1, grain yield, straw yield, biological yield, harvest index ( HI). Data on grain and straw yield were recorded on a plot basis after drying in the sun maintaining 14% moisture, threshing, winnowing and finally converted to grain/straw weight per hectare.