Two field trails were conducted at Mallawi Agricultural Research Station, El-Minia Governorate, Egypt, during 2008/09 and 2009/10 (two plant cane crops) and 2009/10 and 2010/11 (two first ratoon crops) to study the effect of different levels of potassien fertilizer (0.0, 2.0 and 3.0 l/400 l water/fed) as foliar application and 24 kg K2O/fed to soil as a starter dose on quality and productivity of two sugar cane cultivars, i.e. G.84-47 cultivar compared with the commercial one viz. G.T.54-9. A split plot design with four replications was used where, three levels of potassien which consists of (NPK as 0: 8 P2O5: 30 K2O) were arranged in the main plots and the two sugar cane cultivars were allocated in the sub plots. This study was carried out to define the optimal liquid potassium (potassien) level to achieve the highest productivity and quality of the promising sugar cane cultivar G.84-47 as compared with the commercial G.T.54-9 cultivar. The results showed that: increasing potassien fertilizer level from 0 to 3.0 l/fed gave the highest values of stalk diameter, TSS%, purity%, and sugar recovery% as well as millable canes and recoverable sugar yields/fed. Sugarcane G.84-47 variety was better than G.T.54-9 in all the studied traits. The interaction between potassien levels and the two varieties exhibited positive influence on sugar recovery%, millable cane and recoverable sugar yields/fed in the plant cane only in both seasons. Planting G.84-47 variety sprayed with potassien at 3.0 l/fed gave the highest values.