Effects of nitrogen fertilizer and plant growth regulator on stalk yield and bioethanol in sweet sorghum . Maryam Usofzadeh1 *, Mashalla Daneshvar1, Abbas Almodares2 and Hamid Reza Eisvand1

In this study, the effects of nitrogen fertilizer and plant growth regulator (ethephon) application on leaf chlorophyl, stem height and diameter, stalk yield, total sugar and bioethanol of sweet sorghum were determined. Four nitrogen treatments 0, 100, 200 and 300 Kg Urea ha-1 and four ethephon concentrations 0, 800, 1000, and 1200 ppm were applied on sweet sorghum in a split plot on randomized complete block design with three replications. The results showed that interaction of nitrogen and ethephon on stalk yield was significant. The highest stalk yield (30.91 t ha-1) was obtained with the application of N4E4 (300 kg Urea ha-1 and 1200 p.p.m (ethephon) and the lowest (12.15 t ha-1) with control and N2E1 (100 kg Urea ha-1 and 0 ppm ethephon). Maximum amount of total sugar (12.06 %) was obtained at 300 Kg Urea ha-1. The lowest bioethanol was 2423 L ha-1 at 0 ppm ethephon and the highest was 4424 L ha-1 at 1200 ppm ethephon. Based on these results, it is suggested to apply 300 Kg Urea/ha and ethephon at 1200 ppm to have the highest bioethanol in sweet sorghum.  Keywords: Usofzadeh, M., M. Daneshvar, A. Almodares and H. R. Eisvand. 2013. 'Effects of nitrogen fertilizer and plant growth regulator on stalk yield and bioethanol in sweet sorghum stress'. Iranian Journal of Plant Physiology 3 (3), 711-716.