Effects of row spacing on growth and grain yield of early and late sorghum cultivars

Abstract

The effects of row spacing on growth and yield of grain sorghum (Sorghum bicolor (L.) Moench.) were investigated at a constant population density using 5 cultivars of different duration to flowering under dryland conditions in south-eastern Queensland. The row spacings were narrow (0.33 m), standard (1.0 m), and wide-double (1.67 + 0.33 m). Rainfall was plentiful during the tillering and grain filling stages of growth, but a severe water deficit developed at the boot-anthesis stage. The water stress impaired heading and grain set, and grain dry weight was low (40-190 g m-2), with earlier flowering cultivars producing higher yields. There was a cultivar x row spacing interaction for yield; in the earliest flowering cultivar Texas (610SR), which headed before severe stress developed, there was no significant effect of row spacing while in the other cultivars the yield was highest in double row and least in narrow row. There was no detectable difference in soil water available to the plants at any time during growth, but a slightly higher plant water status and faster phenological development in the wider row plants. These responses are related to the fact that the tiller production was least in double row and therefore individual stems had more water available to them.