Effect of Sowing Rate on Agronomic Traits of Sorghum ( Sorghum bicolor Moench) in Southern Kyushu, Japan

Abstract

Newly released sudangrass-type sorghum cv. "Tarzan" was bred for use as a bioenergy-resource feedstuff in Germany. Since the genotype was collected at a high altitudinal site in the Central Africa continent, its early growth is vigorous at low temperature. As vigorous growth at low temperature is derived from high tillering ability, the sowing rate of this genotype should be reduced from the ordinary rate for sorghum. Thus, in the present study, the optimal sowing rate of cv. "Tarzan" in southern Kyushu was determined by the effect of sowing rate at 0.5, 1.0, and 1.5 g.m-2, designated as low (L), middle (M), and high (H) levels, respectively, on growth habit compared with the normal sudangrass cultivar "Roll-king II". Early growth was retarded by heavy precipitation in June, after which the growth was comparable for the two genotypes. Dry matter yield of "Tarzan" increased with higher sowing rate; the H level yield was 1298 g.m-2, and the yield was not adversely affected by the humidity and heat in the summer growing season, compared with "Roll-king II". This suggests that "Tarzan" can adapt to the humid, hot climate in southern Kyushu, and the optimum sowing rate of "Tarzan" should be as low as 1.0 - 1.5 g.m-2, which is less than one-fifth to one-third that of forage sudangrass grown in the region.