Wendy Vance

In the Mediterranean-type environment of south-west WA chickpea is sown into a dry soil profile and rainfall before or soon after sowing is required for germination and seedling establishment. Flowering and podding stages are particularly sensitive to drought stress and consequently rainfall through the growing season is required to ensure adequate soil water reserves to avoid plant water stress. We studied the effect of row spacing (23 cm, 50 cm and 75 cm) on the partitioning of soil water extraction by the chickpea crop at different growth stages. To determine the effect of initial soil water status on row spacing response main plot treatments with (75 mm, simulating summer rainfall) and without pre-season irrigation were imposed in a split plot design to a calcareous loamy earth at Merredin, WA. At sowing, the 1 m soil profile of the irrigated treatment contained only 14 mm more water than the unirrigated treatment, indicating that the pre-season irrigation was ineffective and a large proportion of the applied water was removed as evaporation before sowing, as runoff and drainage were negligible. Nevertheless, the additional soil water significantly improved crop yields through improved early biomass production, even though it was exhausted by pod formation and pod filling. The effect of row spacing on grain yield was not altered with pre-season irrigation, indicating the in season rainfall was more of a condition which led to chickpeas in narrow or wide rows performing better. This was confirmed in two seasons with high and low May to October rainfall. In 2008 (232 mm rainfall) grain yields in wide rows were least, whilst in 2007 (163 mm rainfall) the narrow row spacing yielded less than the wider row spacings.