Determining optimum period of withholding irrigation for inducing maturity of sugarcane (Saccharum spp. hybrid) in Southern Ethiopia

Withholding irrigation before harvesting is important for inducing maturity in sugarcane. The study was carried out to determine the optimum period of withholding irrigation for inducing maturity in sugarcane in southern Ethiopia. Field experiments were conducted on two sugarcane varieties, N Co 334 and B 52 298 by five treatments of withholding irrigation periods for 20, 30, 40 50 and 60 days in randomized complete block design at the crop age of 11.3 months during 2014-15. The data on soil moisture content, top to bottom ratio of Brix in cane juice by hand refractometer, Brix, pol, purity and reducing sugars percent juice, and recoverable sugar percent cane, estimated sugar yield were recorded. Error variances for all characters except top to bottom ratio of Brix and reducing sugars in canes in experiments of both varieties were homogeneous and thus the data were also analyzed in split-plot design with varieties as the main plot and withholding irrigation period (WIP) treatments as subplots. The soil moisture percent differed at different WIPs with lowest at WIP for 60 days. Quality characters, top to bottom ratio of Brix in juice, Brix, pol or sucrose, purity, and sugar recovery percent cane increased significantly with the increase in WIPs, being highest at 50 and 60 days. Reducing sugars percent juice declined significantly with lowest at WIPs for 60 days. Estimated sugar yield increased significantly with the maximum at WIP for 50 and 60 days. The optimum period for withholding irrigation was 50 to 60 days for inducing maturity in sugarcane if not offset by rains. It was, therefore, suggestive that the irrigation could be withheld to sugarcane crop of about 12 months for 50 to 60 days but the quality of sugarcane should be determined before harvesting for obtaining maximum sugar yield in southern Ethiopia