Decision Support Programmes for Assessing the Impact of Irrigated Sugarcane on Water Resources and Profitability

Sugarcane is a major land use in KwaZulu-Natal and Mpumalanga and competes with other crops, as well as industrial and domestic water users, for water resources. Approximately 420 000 ha is currently under sugarcane in South Africa, of which approximately 21% is irrigated, primarily supplying the northern mills of Malelane, Komati, Pongola, Umfolosi and Felixton. In the northern areas where annual rainfall is low (600 to 700 mm), and class A-pan evaporation high (1900 to 2000 mm), large volumes of irrigation water are required by the crop for maximum production, typically of the order of 10 Ml/ha. Elsewhere irrigation supplements rainfall and in many parts of the industry where annual rainfall is moderate (800 to 1000mm) and class A-pan evaporation low (1500 to 1800 mm) volumes of irrigation water required to maximize production are small (5 to 8,5 Ml/ha). The decision on what type of irrigation system to invest in and the appropriate irrigation strategy to be used is a complex one, linked closely to economic return, and influenced by local climate, soils and water availability.