High crop productivity with high water use in winter and summer on the Liverpool Plains, eastern Australia

Abstract. Wereport exceptional productivity and associatedwater-use efficiency across seasons for commercial crops of rainfed spring wheat and grain sorghum growing on stored soil water in Vertosols on the Liverpool Plains, central-eastern Australia. Agreement between the independentlymeasured terms of evapotranspiration (ET) and the soil water balance (in-crop rainfall +dsoilwater)was achievedwithin acceptableuncertainty across almost allmeasurement intervals, to provide a reliable dataset for the analysis of growth and water-use relationships without the confounding influence of water outflow either overland or within the soil. Post-anthesis intrinsic transpiration efficiency (kc) values of 4.7 and 7.2 Pa for wheat and sorghum, respectively, and grain yields of 8 and 7 t/ha from ET of 450 and 442mm (1.8 and 1.6 g/m 2.mm), clearly demonstrate the levels of productivity and water-use efficiency possible for well-managed crops within an intensive and productive response cropping sequence. The Vertosols in which the crops were grown enabled rapid and apparently unconstrained delivery of significant quantities of subsoil water (34 % and 51 % of total available) after anthesis, which enabled a doubling of pre-anthesis standing biomass and harvest indices of almost 50%. Durum wheat planted into only 0.30m ofmoist soil and enduring lower than average seasonal rainfall, yielded less biomass and grain (2.3 t/ha) with lower water-use efficiency (0.95 g/m2.mm)but larger transpiration efficiency, probablydue to reduced stomatal conductance.We argue that cropplanting in response to stored soilwater andmanagement for highwater-use efficiency to achievehigh levels of average productivity of crop sequences over time can have a significant effect on both increased productivity and enhanced hydrological stability across alluvial landscapes