Sweet sorghum (Sorghum bicolor (L.) Moench) can be considered as a cash crop in arid and semiarid regions. High production of syrup, sugar and ethanol yield has made the sweet sorghum an important crop in many developing programs. In this study, the effects of crop top removal, including mechanical, and chemical removal along with intact plants as control with spraying magnesium sulfate (0, 4 and 8 mM) were investigated on juice extraction, sugar content and potential ethanol yield of two sweet sorghum varieties (KFS2, KFS3). Our results indicated that juice extraction increased by top removal and application of magnesium sulfate, ranged from 13.1 to 23.4 m(3) ha(-1). Mechanical and chemical top removal along with spraying magnesium sulfate resulted in greater sucrose and total sugar compared to intact plants. Traits determined in study were identical between 4 and 8 mM magnesium sulfate levels; thus, 4 mM level could apply as the optimum level. In comparison, between the two varieties, KFS3 produced higher amount of extracted juice, juice production efficiency, glucose and potential ethanol yield. Ethephon showed positive effects on juice amount and sugar content as same as mechanical removal. Based on these results, it is suitable to use chemical flowering inhibitors, according to their easy application than mechanical removal. It is concluded that magnesium supply and manipulation of flowering procedure may cause higher sugar accumulation in stalks which is more beneficial for ethanol fermentation.