Cotton's water use
- Cotton’s average irrigation requirement is 6-7 megalitres per hectare.
- Australia’s cotton industry is one of the most water efficient industries in the world.
- Water-use productivity by Australian cotton growers improved by 40% in the decade to 2012.
Cotton’s average irrigation requirement is 6-7 megalitres per hectare (ML/ha) (source: Crop and Pasture Science 2013). This compares to the average water use of rice (11.5ML/ha), fruit and nut trees (5.1 ML/ha) and vegetables for human consumption (4 ML/ha) (source: ABARES).
Australian cotton has the reputation as being the most water efficient cotton industry in the world, thanks to biotechnology and advances in precision irrigation and timing.
Long-term monitoring shows the cotton industry’s significant improvements in water efficiency over time. Water-use productivity by Australian cotton growers improved by 40% in the decade to 2012 (Roth Guy, Harris Graham, Gillies Malcolm, Montgomery Janelle, Wigginton David (2013) cited in Crop and Pasture Science 64, 1033-1048).
The latest industry research shows these trends have continued and that Australian growers have continued to significantly increase yields and decreased irrigation inputs. NSW DPI, in partnership with the Cotton Research and Development Corporation, has been monitoring water productivity in irrigated cotton over the last decade. This shows that:
- A further 10% less water is being used to grow a 227 kg bale of lint.
- The industry’s Whole Farm Irrigation Efficiency has significantly improved and is now 81% compared to 57% in the late 1990s, indicating more water than ever is being used by the crop instead of being lost on-farm.
Research into water use in the industry has continued and confirms continual improvement in water use efficiency, increasing yield while using less water.
The Australian cotton industry has achieved a steady increase in yield from less water over time, meaning more cotton fibre can be produced using less water per hectare than ever before.
Leading cotton producers can now grow nearly two 227kg bales of cotton per megalitre of water – almost double the industry average of a decade ago.
All water used on farm is captured through tail water recycling systems and is reused for subsequent scheduled irrigations.
Water use efficiency
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) breeds cotton varieties appropriate for Australian and regional conditions. Each grower selects the best and most efficient variety for their region and farm.
Water-use productivity by Australian cotton growers improved by 40% in the decade to 2012 (Roth Guy, Harris Graham, Gillies Malcolm, Montgomery Janelle, Wigginton David (2013) cited in Crop and Pasture Science 64, 1033-1048).
The industry’s Whole Farm Irrigation Efficiency has significantly improved and is now 81% compared to 57% in the late 1990s, indicating more water than ever is being used by the crop instead of being lost on-farm.
Cotton is mostly grown in the 350-800mm rainfall zone, which means cotton crops can receive significant amounts of their water needs from rain during the growing season. In 2018-19, about 32% of the cotton crop area was rain-grown, the rest irrigated from ground and surface water sources.
How cotton growers are being more water efficient:
- 70% of growers used soil moisture probes (the highest uptake of all Australian agricultural industries).
- 96% of irrigators improved their furrow irrigation system or changed to an alternate irrigation system.
- 49% of irrigators had changed the flow or size of their siphons.
- 35% of growers had redesigned their fields through laser-levelling to ensure they had uniform, well-drained paddocks. Others used GPS guidance equipment and had positioned storage dams closer to cotton fields to reduce evaporation losses.
- Irrigation channels used for pumping water to fields were lined with clay or non-porous materials to reduce water loss through seepage. Thermal imaging and electromagnetic surveys were used to identify leaking dams, pipes and channels, so they could be repaired.
- Tail water recycling systems were implemented to re-use water.
- Mobile electromagnetic sensors were used for the easy and rapid assessment of soils as to their suitability for irrigation.
- Before planting, growers used sophisticated weather software to forecast the amount of cotton that could be sustained during the season. Zero and minimum-till farming practices were also used to help retain soil moisture.
- Growers used technology (including soil moisture probes, satellites and drones) to inform their decisions and so they only watered the amount needed, when it was needed.
- Farmers changed to alternative irrigation systems, such as centre pivots and lateral move systems, automated syphons and ‘bankless’ channels.
- Evaporation reduction techniques, including the covering of storages and shortening of row lengths, were implemented.
- Unnecessary water storage on farm avoided by only purchasing water as it was needed, and not putting it directly into dry storages which would soak it up.
- Mulching and stubble retention helped to retain soil moisture, reducing the need for irrigations.
- Permanent wheel beds reduced soil compaction and increased water infiltration.
- Adhereing to the Australian cotton industry’s environmental management program – myBMP, which included a water management module covering: water quality, efficiency of storage and distribution for dryland and irrigated farming operations to improve farming practices, and carefully manage natural resources.
- Other practices included irrigating to deficits, using drip and overhead sprinkler systems, better accounting of soil variations, changed bed shapes, using irrigation scheduling probes, furrow irrigation system optimisation evaluations, pump optimisation techniques, and reduced distribution losses.
Some of these alternative systems can achieve labour savings, and with some soil types, water savings (about 30%), but may have significantly higher energy costs associated with water pumping and machine operation. Others offer significant labour savings while maintaining or enhancing water use efficiency.
(Source: The Australian Grown Cotton Sustainability Report 2014)