Farm Table says:
Water-use efficiency and productivity trends in Australian irrigated cotton
What is the problem?
The aim of this review is to report changes in irrigated cotton water use from research projects and on-farm practice-change programs in Australia, in relation to both plant-based and irrigation engineering disciplines
What did the research involve?
At least 80% of the Australian cotton-growing area is irrigated using gravity surface-irrigation systems.
What were the key findings?
This review found that:
- over 23 years, cotton crops utilise 6–7 ML/ha of irrigation water, depending on the amount of seasonal rain received.
- the seasonal evapotranspiration of surface-irrigated crops averaged 729 mm over this period
- over the past decade, water-use productivity by Australian cotton growers has improved by 40%. This has been achieved by both yield increases and more efficient water-management systems
- the whole-farm irrigation efficiency index improved from 57% to 70%, and the crop water use index is >3 kg/mm.ha, high by international standards
- yield increases over the last decade can be attributed to plant-breeding advances, the adoption of genetically modified varieties, and improved crop management
- there has been increased use of irrigation scheduling tools and furrow-irrigation system optimisation evaluations. This has reduced in-field deep-drainage losses
- the largest loss component of the farm water balance on cotton farms is evaporation from on-farm water storage
Some farmers are changing to alternative systems such as centre pivots and lateral-move machines, and increasing numbers of these alternatives are expected.
The optimisation of interactions between water, soils, labour, carbon emissions and energy efficiency requires more research and on-farm evaluations.
Standardisation of water-use efficiency measures and improved water measurement techniques for surface irrigation are important research outcomes to enable valid irrigation benchmarks to be established and compared.