Mineral gypsum (CaSO4.2H2O), a promoter of biomass production of sweet sorghum

The sweet sorghum is an alternative bioenergy crop for ethanol production in the off-season of sugarcane in areas where crops are renewed in winter, especially in the Northeast of Brazil. However, in these areas the soil acidity and low levels of basic cations on the subsurface are responsible for reduced productivity of sorghum. The objective of this study was to evaluate the effect of mineral gypsum on nutrients uptake, agricultural/ industrial productivity and production of ethanol from sweet sorghum cultivar IPA 467-4-2. Therefore, a field experiment was set up in Ultisol (Argissolo Amarelo distrocoeso), arranged in randomized blocks, consisting of five treatments as: 0, 2, 4, 6 and 8 Mg ha-1 (ton/ha-1) of mineral gypsum in four replications. Results showed that mineral gypsum can promote the percentage and Ca2+ content and, conversely, reduce percentage and K+ content in shoots of sorghum. The gypsum application increased yield of fresh and dry mass of sweet sorghum, variety IPA 467-4-2, besides increasing the theoretical yield of ethanol. The maximum yield of fresh, dry mass and ethanol were 44373.64 kg ha-1, 9056.43 kg ha-1 and 2032.18 L ha-1, respectively. The recommended dose of maximum agronomic efficiency was approximately 5.5 Mg ha-1, suggesting gypsum as a raw material in appropriate management of sweet sorghum, especially in soils with high acidity in the subsurface.