What influence does summer rainfall and stubble retention have on wheat production in Southern farming systems?

Abstract

Southern Australian broad-acre farming systems are characterised by low frequency, high intensity summer rainfall, and high frequency, low intensity winter rainfall. The contribution of out-of-season rainfall to wheat yield is largely unknown for southern farming systems. An experiment was conducted in which different quantities of summer rainfall (control (0mm), 50mm and 100mm; applied through trickle irrigation) was combined with four stubble treatments (bare, standing (2t/ha), and mulched (2t/ha and 5t/ha)) in a factorial field experiment to determine their influence on capture and efficiency in the use of resources and yield components. Stubble did not influence the ability of the soil to retain moisture in the profile. Summer rainfall significantly contributed to increased soil moisture at sowing deep in the soil profile (50-100cm). Relative to the control, biomass water use efficiency was the same for all summer rainfall treatments, the additional subsoil moisture contributed to increased early crop growth and radiation-use-efficiency and increased yield by 0.5t/ha.