A comparison of irrigated maize growth in southern New South Wales on sites with and without a preceding fallow

Abstract

This experiment was carried out on a grey cracking clay soil near Griffith in southern New South Wales. Maize grown after a two year fallow produced 2.7 t/ha or 45% more grain than maize grown on a continuously cropped site. This difference occurred despite large fertilizer inputs and similar management procedures. The yield differences resulted from increased plant establishment (20%),kernel numbers per cob (26%), and kernel size (11%) in the fallow area. However, experimental results were mostly inconsistent with our initial hypothesis that restricted root growth and soil water uptake were limiting yields on continuously cropped sites. Water use was measured throughout the season with a neutron probe, but no differences in depth or amount of soil water extraction were detected. Root length density and leaf water potential measurements indicated that plant water relations were similar for the two sites and so this did not seem to account for the improved yield from the fallowed site.