SECTION 5
IRRIGATION Th is se c t i o n brou g ht t o y o u i n as soci a t i o n wi t h
Irrigation has been a central feature of agriculture for at least 5000 years and is the product of many cultures. In 2000, the world area of irrigated land was estimated at 2.8 million km² – by 2012, this estimate had increased to 3.2 million km², an irrigated area about the size of India (thankfully not all of the world’s irrigators operate under ‘India’ style farm subsidy policies).
Irrigation in the Australian sugarcane industry O Drawn from SRA’s Irrigation of Sugarcane Manual
T
HE need for irrigation has been recognised in sugarcane for over 100 years. In the Burdekin, Bundaberg and Central regions, groundwater and surface water sources have been used from the late 1890s. There were a number of drought years around that time that proved the importance of a regular water supply. The irrigated area in Queensland has gradually risen from less than 9000 hectares in 1933 to 192,000 of irrigated sugarcane in 2008–09 (ABS, 2009). Over 40 per cent of the Queensland sugarcane crop is irrigated which accounts for 60 per cent of total cane production. The requirement for irrigation varies by region (Table 1). Areas with low levels of effective rainfall (e.g. Burdekin) see the greatest response to applied irrigation, while areas with
Drip tape being installed.
(PHOTO: Steve Attard)
50 — AUSTRALIAN SUGARCANE ANNUAL 2019
high amounts of effective rainfall are unlikely to benefit economically from irrigation. Within districts the need for irrigation can also vary from season to season. Full irrigation is a term used to describe the irrigation practice in areas of low effective rainfall. In these areas most of the crop’s water requirement will come from irrigation. Regions with higher levels of effective rainfall and where irrigation is used strategically to stabilise and increase yields are often called supplementary irrigated. Compared with fully irrigated areas, supplementary irrigation supplies a smaller proportion of the crop requirement.
Crop response to irrigation Given adequate growing conditions, approximately 100 mm (1 ML/ha) of water (irrigation or rainfall) is needed to produce 10 tonnes of cane per hectare. Very efficient irrigation practices can use the same amount of water to produce up to 15 tonnes of cane per hectare. Cane grows fastest under conditions of adequate moisture, sunlight and temperature
Furrow irrigation – water is introduced to the furrows from open channels, a gated pipe or plastic fluming.
