Investigations on the effect of different fertilizer treatments on the yield and some technological properties of sweet sorghum (Sorghum bicolor (L.) Moench var. saccharatum) used as an energy crop

Two individual pot experiments were conducted on sweet sorghum grown under outdoor. The first was a biomass and ethanol study to determine the effect of NK fertilisation levels and the second was a grain characteristic to determine the effect of NP fertilisation levels on sweet sorghum (Sorghum bicolor (L.) Moench var. saccharatum) (Keller cv.) yield. The experiments were carried out at Ege University, Faculty of Agriculture, Department of Field Crops, Izmir/Turkey, during the summer growth seasons of 2013 and 2014. In the first experiment, sorghum seeds were sown with different fertilization levels of N (0, 50, 100, 150, 200 kg N ha-1) and four potassium (0, 50, 100, 150 kg K2O ha-1) levels. For the second experiment different fertilization levels of N (0, 50, 100, 150, 200 kg N ha-1) and four phosphorus (0, 50, 100, 150 kg P2O5 ha-1) levels applied. Nitrogen fertilizer was applied in two equal doses in both experiment. Potassium or phosphorus was mixed with soil and supplied as a single application. Results indicated that the effects of nitrogen and potassium treatments in the first experiment and the effects of nitrogen and phosphorus treatments in the second experiment on all characteristics tested were significant. Application of the higher rates of N and K or P treatments, increased the fresh biomass, ethanol, grain yields and improved the forage quality compared to the control treatment. Based on these results, in the first experiment, the combination of N150 and K100, and, the second experiment, the combination of N200 and P100 were proved to be the best fertilizer levels for sweet sorghum biomass, ethanol and grain yields, respectively, under Mediterranean ecological conditions of Izmir.