Acceso usuarios
D.M. Bakker, G. Plunkett, J. Sherrard
The introduction of irrigation in the Ord River Irrigation Area (ORIA) in the North West of Western Australia resulted in rising water tables in many parts of the ORIA. Commercial sugar cane production commenced in 1995 in the area, which exacerbated the problem caused by the longer growing and irrigation season and the large irrigation applications. Rising water tables are associated with deep drainage from paddocks and irrigation infrastructure. Improving the irrigation application efficiency (IAE) was identified as a manageable objective for sugar cane growers that is expected to reduce deep drainage. Existing irrigation practices were monitored and a surface irrigation model (SIRMOD) was used to simulate these irrigations. The lack of accurate infiltration parameters normally limits the extrapolation of SIRMOD simulation results to different irrigation scenarios. It was found that the infiltration into the Vertisols of the ORIA could be properly described by simple infiltration functions which were dependent on the soil moisture deficit (SMD) at irrigation as well as the shape of the irrigation furrow. The function described as Instantaneous Crack Fill (ICF) was appropriate for furrows with broad-based �U�-shaped furrows while a non-ICF described the infiltration behaviour of deeper �V�-shaped furrows. Summary tables were generated to illustrate the relationship between SMD, inflow rate, furrow length and irrigation duration for �U�-shape and �V�-shape furrows of Vertosols in the ORIA. From the tables it was determined that gains of up to 20% can be achieved in the IAE compared to the current situation.
