Ripening Response of Sugarcane Varieties to Chemical Ripeners and Economic Benefits during the Early Period of Harvesting at Wonji-Shoa and Metahara Sugarcane Plantations, Central Rift Valley of Ethiopia

Abstract

Wonji-Shoa and Metahara sugarcane plantations experience reduced sucrose content (%) during the starting period of sugarcane crushing due to the combined influence of high (>27°C) temperature and the presence of high residual soil moisture. Studies elsewhere showed the potential of chemical ripeners in boosting the sucrose content (%), where natural ripening is deterred by these challenges. Accordingly, a field experiment was conducted to evaluate the responsiveness of selected sugarcane varieties to chemical ripeners at both plantations. The treatments consisted of a factorial combination of four sugarcane varieties (B52298, NCo334, C86-56, and SP70-1284) and six ripener treatments: (1) Ethephon™(720 g ai ha−1), (2) Fusilade Forte™(25.6 g ai ha−1), (3) Moddus™ (250 g ai ha−1), (4) Ethephon™ (720 g ai ha−1) + Fusilade Forte™ (25.6 g ai ha−1), (5) Moddus™ (250 g ai ha−1) + Fusilade Forte™ (25.6 g ai ha−1), and (6) Unsprayed (control). The experiment was laid out in a randomised complete block design in a factorial arrangement with three replications. The results showed a significant ( $p=0.025$ ) and highly significant ( $p=0.001$ ) variety by ripener interaction in stalk height and sucrose content, respectively, while the main effect ripener highly significantly affected stalk weight ( $p=0.001$ ) and sucrose yield ( $p=0.003$ ). The variety C86-56 sprayed with combinations of Ethephon™ + Fusilade Forte™ and Moddus™ + Fusilade Forte™ had the shortest stalk heights of 1.27 and 1.29 m, respectively, compared with the control. Ethephon™ + Fusilade Forte™ combination resulted in the highest reduction of stalk weight (8.36%), while the lowest was recorded in the sole Moddus™ treatment (6.31%). From the ripener treatments, the Moddus™ + Fusilade Forte™ combination and Ethephon™ + Fusilade Forte™ combination improved sucrose yield by 1.42 and 1.34 t ha−1, respectively, compared with the control. However, in economic terms, the Moddus™ + Fusilade Forte™ combination treatment resulted in the highest marginal rate of return of 1244%. Therefore, the Moddus™ + Fusilade Forte™ combination ripener treatment was found to be promising to be evaluated at a commercial scale on immature sugarcane varieties B52-298, NCo334, and SP70-1284.