Effect of fertilizer mechanism and harvest time on juice volume, sugar brix and bioethanol in three varieties of sweet sorghum (Sorghum bicolor)

An experiment was conducted during the rainy season of 2014–2015 at Experimental Garden of Indonesian Research Cereals Institute, Gowa, Indonesia to evaluate the effect of fertilizer nutrient release mechanism and harvest time on volume and sugar content of juice and bioethanol yield of 3 varieties of sweet sorghum (Sorghum bicolor (L.) Moench). The experiment was performed in the field using split-split plots design, where the main plot received mechanism of fertilizer that consisted; fast release (P₁), slow release (P₂) and combination of both fast release and slow release (P₃), while the sub-plots received harvest time treatments, viz. Harvesting before physiological maturity (W₁), Harvesting at the exact physiological maturity (W₂) and Harvesting after physiological maturity (W₃), and in the sub-sub-plots 3 varieties viz. ‘Numbu’ (V₁), 'super 1’ (V₂) and 'super 2’ (V₃). The results showed that fertilization with P₃ gave the best average results of juice volume and others parameters compared to P₁. P₂ fertilization gave the best results of sugar content, while P₃ gave the best results of bioethanol produciton. W₁ gave the best results of volume of juice, while W₃ and W₂ gave the best results of sugar content. W₁ and W₃ recorded the best results on bioethanol. V₂ varieties recorded the highest volume of juice.