Identifying the trends and drivers of water productivity in Australian cotton through benchmarking (includes CottonInfo technical lead Ben Crawley)
Improving water productivity is a high priority for Australian agriculture, especially given increasing competition for access to freshwater resources. The Australian cotton industry is a global leader in water use efficiency and is committed to continual improvements in water productivity and demonstrating responsible use of our shared natural resources.
NSW Department of Primary Industries (DPI) is working with the Australian cotton industry to assess and benchmark water productivity of cotton. The benchmarking helps the industry to improve the productive and sustainable use of water by using the results to track progress towards the industry’s target and to identify options for improvement.
This project has continued the long-term monitoring of water use in the cotton industry, delivering annual water productivity and water sustainability benchmarks for irrigated and rainfed cotton based on grower surveys.
Throughout the benchmarking period, water productivity of Australian irrigated cotton has increased from 0.60 bales/ML in 1997 to 1.22 bales/ML in 2021. Water productivity in 2021 ranged from 0.79 to 1.61 bales/ML with the top 20% of growers achieving 1.41 bales/ML or more. These results indicate potential for most growers to increase water productivity through improved water management and increased yield.
Data from the growers surveyed showed the annual rate of productivity improvement was 9% between 1997 and 2007, however it has slowed to an average of 0.6% since 2007.
The Australian industry’s average water productivity in 2021 was 30% higher than the maximum achieved in 1997.
Australian cotton water sustainability indicators have improved significantly. The water used to produce one bale of cotton in 2021 was 0.72 ML/bale, which is less than half the water used of 1.54 ML/bale in 1997.
On a global scale, Australia is a leader in cotton water productivity and sustainability. The average water productivity of Australian cotton for 2001 to 2021 is 1.08 bales/ML. This is 2.25 times the global average of 0.48 bales/ML, based on the latest available data published in 2011. The long-term average water consumption in Australia for 2001 to 2021 period was 0.93 ML/bale, which is less than half the global average of 2.07 ML/bale equivalents reported in 2011.
Improvements in water productivity of irrigated cotton in Australia are the result of increased yield, reduced water inputs and increased irrigation efficiency, during a period when rainfall was declining.
For rainfed cotton, a literature review of water productivity resulted in the adoption of a model to quantify water productivity and water sustainability. Crop water productivity is calculated as lint yield (kg) divided by total crop water use and is expressed as kg lint/mm. The inverse of crop water productivity is water sustainability indicator, which is expressed as mm/kg lint. The total crop water use is estimated as the sum of plant available water at sowing and total in-crop effective rain. The total plant available water at sowing can range from zero to 100% of plant available water capacity.
The average water productivity of rainfed cotton produced between 1995 and 2021 was 1.84 kg lint/mm (0.81 bales/ML). The range is between 0.4 – 5.3 mm/kg lint and the top 20% of growers achieved 2.51 kg/mm (1.06 bales/ML) or greater.
The water sustainability indicators for rainfed cotton suggest it used an average of 0.72 mm to produce each kg of cotton lint (1.63 ML/bale) for the same years. The top 20% of growers achieved 0.40 mm/kg (0.91 ML/bale).
The project activities and results have been widely communicated to growers, industry and other researchers. This has occurred through scientific publication, conferences, popular press, industry magazines, webinars, radio, YouTube and presentation both one on one and in groups.
The Technical Lead in the CottonInfo team has successfully supported key water research projects, facilitated collaboration with new research consortia, updated relevant myBMP modules, communicated project activities and results, and built capacity of growers and their advisers via training sessions, presentations and various multimedia platforms.
DAN2002 has fostered collaboration with a wide diversity of partners, including local, national and international collaborations to improve and extend capacity to assess and increase water productivity and sustainability of cotton and other crops.
The project has made the following key recommendations for the industry:
- While the industry is approaching the average water productivity target of 1.32 bales/ML by 2023, the individual grower’s performance is highly variable, and the overall rate of improvement is slowing. New approaches are required to understand what factors are limiting water productivity improvement and what are the strategies used by the top 20% of growers do to achieve high water productivity.
- Given that to date the average gross productivity water use index has been referred to by the industry as ‘the benchmark’, the industry should seek to adopt an aspirational benchmark of lifting water productivity to the level achieved by the top 20% of growers.