WATER SAVINGS AND WATER ACCOUNTING IN IRRIGATED SUGARCANE

WHILE IT is more abundant in Queensland than in many states in Australia, water is rapidly becoming the most limiting factor for development in the State and scrutiny and accountability will increase for all users of water—agricultural or otherwise. The general perception in the sugar industry is that more water means greater profits but this is not always true. This paper reviews both published and unpublished data to indicate how the industry could consider better ways of accounting for water use as well as ways to reduce water use under certain circumstances. The research indicates that it is possible to estimate crop water use with sufficient accuracy to irrigate only as much as required to meet crop water demand. In many cases this would be the first step to reducing water use without risk of losing yield. A second but more risky approach is to provide less water than the crop actually needs and allow roots to take up the balance from water stored deep in the profile. Experiments are cited where irrigation was stopped or reduced without reducing sugar yield because roots were able to access water deep in the profile. A third approach is to actually aim for reduced cane yield knowing the capacity for sugarcane to accumulate sucrose preferentially under conditions of mild water stress. The results of field experiments are cited to indicate how sucrose accumulation can be encouraged while reducing stalk elongation and cane yield leading to enhanced CCS and possibly sugar yield at the same time as saving water. The use of a web tool called WaterSense for managing water in either of these ways is discussed.