Water use efficiency and soil water availability for sugarcane

Competition for water, increasing costs and environmental concerns require that major users of water achieve best-practice in tenns of efficiency of water use. Soil hydraulic processes, particularly those affecting water storage and uptake, play an important role in the efficiency of water use, but their measurement is a major challenge to obtaining reliable estimates of rainfall and water use efficiency. The aims of this paper were (i) to develop a modelling technique to detennine maximum rooting depth and total plant extractable water capacity (PAWe) from plant extension measurements; (ii) to use this technique to produce soil hydraulic input parameters for the APSIM-Sugarcane model for a number of soils in the Bundaberg region; and (iii) to simulate the impact of soil type on rainfall and water use efficiencies. It was shown that leaf or stalk elongation measurements combined with conventional soil hydraulic measurements and modelling can expedite the characterisation PAWC for determining rainfall and water use efficiencies. Interactions of soil type and yearly climate on these efficiencies were considerable. The prevalence of these interactions detracts from the use of generalisations. PAWC and maximum rooting depth could be determined rapidly from existing soil surveys and stalk growth. This will enhance benchmarking and the establishment of improved management strategies to best use water in sugar industries worldwide.