Using grain sorghum for crop rotation in southern Australia: a farm approach to system development

The development of herbicide resistance is a major problem associated with continuous cropping systems in southern Australia. The use of a chemical fallow, followed by a summer-grown crop (e.g. grain sorghum), provides an option for controlling winter-grown weeds and reducing use of selective herbicides. This paper reports an experimental approach taken by a farming enterprise in assessing the suitability of grain sorghum ( Sorghum bicolor) in a continuous cropping rotation in the Wimmera region of Victoria. Results are given from five seasons (1995–1999) where sorghum was grown in large unreplicated trials with a final average yield of 2.4 Mg ha −1. Also a replicated experiment was conducted in one of the seasons (1996–1997), where the sorghum grew almost entirely on stored soil water, extracting about 150–170 mm from 115 cm depth: here the grain yield of the sorghum was 1.6 Mg ha −1. The soil water storage in this cracking clay soil (HyperCalci-Chromic Vertisol (Grumic)) was about 250 mm (0–140 cm depth) at the end of the winter prior to sowing. The yields of winter crops grown immediately after sorghum harvest were also recorded, suggesting that the water use by the preceding sorghum crop did not have an adverse effect on the growth of these winter crops. Thus, the use of summer crops such as sorghum in the Wimmera region may provide another approach for integrated weed management in a continuously cropped system.