Water continues to be a major constraint for cotton production systems. There is increasing pressure to improve the water use efficiency (WUE), especially of the furrow irrigation systems used by the majority of cotton growers. Farming systems, stubble management, furrow length and slope and the flow rates are all components of the system that can be manipulated to achieve higher application and distribution efficiencies under furrow irrigation.

Previous work has shown that there is significant room for improvement in both crop water use efficiency and whole farm irrigation efficiency within the cotton production system. Crop water use efficiency (CWUE) was shown to vary between 1.8kg/ha/mm and 3.2kg/ha/mm. Whole farm irrigation efficiency was shown to vary between 20 % and 80 % with an overall average of 57 %. A key approach to improving whole farm WUE is to develop an integrated approach to water management, particularly to identify factors contributing toward high crop WUE and irrigation efficiency. In addition to irrigation, in-season rainfall and stored soil moisture contribute to meeting the crop water requirement. Strategies should be developed to maximise the use of water from in-season rainfall and stored soil moisture and to improve irrigation efficiency. This will benefit the industry by saving irrigation water and enhancing the efficiency with which water is used.

For this project the take home messages are

1. More work is required to understand extraction of water under skip row cotton.

2. HydroLOGIC includes the water use efficiency calculator and this feature will be enhanced in later versions. The capacity for HydroLOGIC so account for whole farm water use being developed.

3. Data have been collected to validate the Penman-Monteith equation and this will be completed in future.

4. Retained stubble systems offer benefits in terms of reduced loss of sediment, improved water infiltration and better early season growth. However this may be countered by the need for careful management to avoid water logging, though there are strategies to do this.

5. Investigation of the effects of vetch rotations on irrigation and water use showed slightly enhanced water holding capacity of soils following vetch rotations.

6. Resurveying the growers involved in the initial WUE Benchmarking study has been planned out and surveying will be done by Mitch Carter (NSW DPI)

The core goals of this project have now been included in CSP164C.