Management of soil water for wheat production in Western Australia

Abstract. Spring wheats are sown in autumn and mature under conditions of spring water deficits in Western Australia. While grain yields are very small (averaging 1.05t ha^-1), water-use efficiencies ( WUE ) of crops grown with good management compare favourably with the rest of Australia at 10 kg grain ha^-1 mm^-1. Major water loss, calculated at an average 40% of growing-season rainfall, occurs through evaporation from the soil surface, and in some years significant losses also occur through deep drainage on sandy soils. Evaporation losses can be reduced by stubble retention and adding gypsum to improve filtration on structurally unstable, fine-textured soils. More general increases in crop water use occur through all agronomic factors which result in rapid and uniform plant cover as early as possible after break of season. This includes adequate fertilization, weed control and narrow row-width. Wheat crops sown after pasture and grain legumes consistently outyield all-cereal rotations.