In recent years water use has become an important issue for the cotton industry mainly due to prevailing drought, competition with other water users and environmental concerns. Therefore water use efficiency is a critical issue for the Australian cotton industry and avenues for improving irrigation efficiency (IE) and crop water use efficiency (CWUE) need to be explored. Total water inputs to an irrigated cotton farm come from in-season rainfall, irrigation and stored soil moisture. A integrated management of these water inputs will assist in improving the efficiency of use of irrigation water, reduce salt inputs to the farm and reduce the risk of off-farm movement of agrochemicals. The results of past studies show that crop rotation has a number of advantages particularly in terms of soil moisture conservation. The amount of moisture stored in the soil depends on the water holding capacity of the soils and infiltration capacity. By using appropriate crop rotation and stubble management, a portion of pre-season rainfall can be stored in the soil profile to be used for future cotton crops. Further infiltration capacity of soils can be improved to utilise “in season” rainfall efficiently.

The effect of the previous crop and tillage method on water use efficiencies was investigated using the existing farming system trials. There was no significant difference between treatment for in-season rainfall use efficiency and total amount of irrigation water used for evapotranspiration. Cotton CWUE did, however, differ between cropping systems. Cotton CWUE's were in the order of minimum-tilled cotton-wheat (average of 2.30 kg of lint/ha/mm)> minimum-tilled continuous cotton (average of 2.12 kg of lint/ha/mm)> intensively-tilled continuous cotton (average of 2.07 kg of lint/ha/mm). Highest plant available water was observed in minimum tillage with rotation treatment. There was additional 26mm of plant available water in minimum tillage with rotation systems compared to maximum tillage continuous cotton. These results clearly indicate that the crop rotation and tillage strategy have beneficial effects on water use efficiencies of irrigated cotton.

Cotton farmers need strategies and tools to assist in monitoring and analysing water use with a view to improving efficiency. A standard method for measuring, recording and analysing water use is necessary to make a valid comparison of water use efficiencies between fields, properties and seasons. A user-friendly software tool was developed to assist cotton growers to record, analyse and assess the performance of individual fields and whole farm water use efficiency using readily collected on-farm data. Both production and quantitative water use efficiencies are considered, including the overall irrigation water losses within the farm. This system enables irrigators to identify the fate of water within the farm, identifying points of loss and potential areas for improvement. This system has been integrated into HydroLOGIC software.