Estimating irrigation duration for high performance furrow irrigation on cracking clay soils

Selection of an appropriate combination of flow rate and time to cut-off is critical to the achievement of high performance furrow irrigation. For the cotton growing regions of Australia the ready availability of land and the relative scarcity of water impose a constraint not present in all surface irrigation areas. In this situation the objective is to improve water use efficiency by maximising application efficiency. In this paper, simulations employing this strategy and historical furrow irrigation data have shown that application efficiency increases with flow rate up to a point where no further increase in efficiency is possible. They have also shown that for any field there is a simple linear relationship between time to cut-off and the time for the advance to reach mid-way down the field. This relationship provides a simple and robust guide for the selection of time to cut-off that requires no knowledge of the flow rate or soil moisture deficit. Application of the relationship delivers a significant increase in efficiency over that resulting from usual grower practice.