Managing crop residues to improve wheat growth and yield

George Swella

    Research output: ThesisDoctoral Thesis

    373 Downloads (Pure)


    [Truncated abstract] Residue ground cover and architecture alter the surface microclimate, and thereby impact soil water conservation. In Mediterranean-type climate, it is not clear how much residue is needed in no-till (NT) systems and whether standing or flat residue is preferred. The general objective of this study was to understand the influence of stubble cutting height and architecture on wheat growth, capture of rainfall and soil water dynamics, and soil temperature. The first aim of the current research was to investigate the effect of stubble height and architecture on rainfall capture during high and low rainfall events, and subsequent evaporation from the soil surface.Three experiments were conducted sequentially at Shenton Park Field Station at The University of Western Australia. The first experiment used a rainfall simulator to apply water, followed by sprinkler irrigation in the second and a rainfall event in the third. The results showed that high levels of stubble retention, particularly flat stubble, prevents water reaching the ground following low rainfall events but maximises soil water retention after high rainfall events when compared with lower levels of residue. More standing and flat stubble recorded higher soil water storage throughout the soil drying cycle compared with other stubble combinations and bare soil. This study has shown that tall (30 cm) standing stubble increases interception of rainfall compared with short residues. Intercepted rainfall can evaporate directly (e.g. with light rain) or run down the stubble into the soil. The second objective was to determine the effect of stubble-cut height (standing stubble) on spatial variability of soil water. This study was conducted at Shenton Park Field Station by measuring soil water following low and high rainfall events. Across all dates, and row positions, tall-cut stubble (25 cm) combined with 2 t ha–1 flat stubble had more soil water to 20 cm depth than other treatments combinations, and the effect was enhanced in the stubble row (in-row) compared with inter-rows. This difference in soil water content was more evident in the 10–20 cm soil layer, compared with the upper (0–5 cm) and middle (5–10 cm) layers. This indicates that standing stubble contributes to deeper water penetration under the stubble row, which would reduce evaporative losses...
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2014


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