Response of kabuli chickpea ( <i>Cicer</i> <i>arietinum</i> L.) to sowing rate in Mediterranean-type environments of south-western Australia

The effect of sowing rate (60–320 kg/ha) on the growth and seed yield of kabuli chickpea (cv. Kaniva) was assessed at 11 sites for 4 seasons in the cropping regions of south-western Australia. The economic optimum plant density and yield potential were estimated using an asymptotic model fitted to the data and calculating the sowing rate above which the cost of additional seed was equivalent to the revenue that could be achieved from the extra seed yield produced, assuming a 10 and 50% opportunity cost. On average for all sites and seasons, plant densities ranged from 10 plants/m2 when sown at 60 kg/ha to 43&amp;nbsp;plants/m2 when sown at 320 kg/ha. Assuming a mean seed weight of 400 mg and a germination of 80%, then on average 75% of viable seeds sown (or 60% of sown seeds) established as plants. The poor establishment rates are thought to be associated with reduced viability caused by mechanical damage, storage conditions, fungal infection in the soil, and unfavourable seed bed moisture and temperatures. In general, there was a positive relationship between sowing rate and seed yield. Seed yield increases at higher sowing rates were mainly associated with the greater number of plants per unit area. There were fewer pods per plant at higher sowing rates, but there were more pods per unit area. Changing the sowing rate had little effect on mean seed weight and the number of seeds per pod. The economic optimum plant density varied from 8 to 68 plants/m2, depending on the location, but the mean (27&amp;nbsp;plants/m2) was within the range currently recommended in southern Australia (25–35 plants/m2). Due to the low establishment rates observed in this study, we estimate a sowing rate greater (160–185 kg/ha) than currently suggested (110–160 kg/ha) to achieve this density. There was a strong relationship between economic optimum plant density and seed yield potential ( r 2 = 0.66, P &amp;lt;0.01), which allows an estimation of the most profitable sowing rate, depending on the seed yield potential of the site. For most crops yielding about 1.0 t/ha in southern Australia, a plant density of 25 plants/m2 is most profitable, while in higher-yielding situations (&amp;gt;1.5 t/ha) plant densities &amp;gt;35&amp;nbsp;plants/m2 will produce the most profit.