A physiological basis for response of sugarcane to drying-off before harvest

In irrigated sugarcane production, water is usually withheld prior to harvest to dry the field and make it suitable for harvesting operations, and to raise both the sucrose concentration of the cane and the sucrose yield. The optimum length of the drying-off period will depend upon the rate of development of crop water deficit and the associated changes in sucrose yield, cane yield and sucrOse concentration. This paper reports the results of two seasons of drying-off experiments conducted in the Burdekin delta area, with the aim of improving knowledge of how sugarcane responds to varying lengths of drying-off before harvest. Some of the key findings are: 1) Sucrose concentration changes within a few weeks of drying, whereas more prolonged drying is required to lower cane yield. While stalk desiccation under drying-off lowers cane yield, this is mitigated somewhat by a greater proportion of the stalk being millable. 2) Increases in sucrose concentration can be attributed equally to increases in dry matter content and sucrose dry matter concentration. These changes are most noticeable at the base and near the top of the stalk. 3). Interruption of drying-off by rain can reverse increases in sucrose concentration, due to resumption of stalk growth. The improved understanding from these experiments can be used by farmers to manage the drying-off period to maximise profitability.