Grain Yield of Sorghum Cultivars in a Double Cropping System

Field experiments were conducted at the experimental field of Kyushu University, northern Kyushu in 1996 and 1997 to investigate the possibility of a double cropping of sorghum using early maturity cultivars. The effects of sowing date (early or late) and the cultivar on the yield were also examined. On the average, grain yield from double cropping was 556 g m−2 in 1996 and 746 g m−2 in 1997. Sowing date greatly influenced the major traits of the summer crop, but not significantly those in the spring crop, except for the days to heading. Late summer sowing decreased grain yield as much as 41.9%, decreased 100-grain weight by 22.4% and extended days to heading. Early sowing, early in April and late in July or early in August, is recommended for spring and summer crops, respectively, in a double cropping system to obtain a high grain yield. SA 403, D12, C8, C9, D5 C10-1 F4 line and D5 × C8 (F1 hybrid) were considered to be suitable for a double cropping system.