Assessment of lateral depths and irrigation water levels on yield, yield parameters and biyoethanol content in sweet sorghum

Abstract

Abstract In this study, it was aimed to evaluate the effects of different lateral depths and irrigation treatments on the bioethanol yield and yield components of the sweet sorghum (Sorghum bicolor L.) in the subsurface drip irrigation method. The experiment was carried out in three replications in a randomized block trial design in 2020 and 2021 in Antalya, Turkey. In irrigation treatments, three different irrigation water levels in which 100%, 66% and 33% of the amount were applied as irrigation water (I1, I2, I3, respectively), when the cumulative reference crop evapotranspiration reached 25±5 mm and lateral depth combinations in which the laterals were placed at two different depths, 25 cm and 50 cm (D1 and D2, respectively) were used. At the end of both years, a statistical difference (p<0.01) was determined between the mean yield components (forage, hay, juice and sugar yield) of different irrigation water levels. As the applied irrigation water level increased, the yield components also increased. While the interaction of lateral depth and irrigation water level affected forage and hay yield in the second year, sugar and juice yield values in the first year. In this study, it was determined that the difference in the effects of the interaction between the years was due to the irregular temperature increases in the second year climate, and the lateral depth of 50 cm was more suitable in drier conditions. At the end of two years, the bioethanol yields and evapotranspiration (ET) obtained in D1 treatments at different irrigation levels varied between 440-2962 L ha-1 and 105.1-473.0 mm, respectively, while it varied between 440-3222 L ha-1 and 105.1-473.0 mm in D2 treatments, respectively. The highest bioethanol yield in the first year was obtained from D1I1, D2I2, D2I1 treatments, while in the second year, from D2I1 was obtained. Considering the I1 treatments, more evapotranspiration was realized in the D1 despite the same amount of irrigation water applied in both years. In addition, when the applications that were irrigated at the same amount at 25 and 50 cm lateral depths in both years were compared, it was determined that water productivity (WP) and irrigation water efficiency (IWP) values obtained at 50 cm lateral depth were higher, except for I3. In this study, it was determined that a lateral depth of 50 cm was more suitable for maximum bioethanol yield, especially in warmer climatic conditions. At the same time, I1 and I2 irrigation levels have been suggested, depending on climatic conditions.