Survey of Irrigation Scheduling Practices in the South African Sugar Industry

Effective irrigation scheduling is a prerequisite to optimising the use of expensive irrigation water for sugarcane production in South Africa. Accurate irrigation scheduling is not widely practised in the sugar industry despite the many scheduling tools available to sugarcane growers. This leads to very low water use efficiencies (WUE) of approximately 50% of what could be achieved theoretically (Olivier and Singels, 2003). Irrigation scheduling can be defined as a programme of irrigation determining the amount of water and timing of application. Schedules can be classified as fixed (amount and cycle fixed for entire growing season), semi-fixed (amount and cycle are changed a few times to accommodate rainfall and significant seasonal and crop age induced changes in water demand) or flexible (amount and cycle are changed daily or weekly according to calculated water budget based on recent crop and weather conditions). Scheduling methods aim to maintain the soil water content in the optimal range by direct monitoring of soil water content or by estimating the soil water content through water budgeting.