Relation between seeding times and stem yield of sorghum in cold region in Japan

The seeding time is an important factor affecting the process of stem yield. Nevertheless, details related to the optimum seeding time to maximize the stem yield of sweet sorghum have not been studied. This study elucidated information necessary to ascertain the optimum seeding time to obtain the maximum stem yield. We conducted an examination with three seeding times at intervals of two weeks, ranging from late May to mid-June for four years during 2009–2012, and we analyzed the relation between seeding times and stem yield based on internode characteristics of stems using two sorghum cultivars with different maturity: ‘Kazetachi’ and ‘Wray’. Differences were observed in the respective relations between the seeding times and the stem yields. For Kazetachi, the dry matter yield increased with the earlier seeding time. Thus, to expand the growing period, an earlier seeding time with good establishment is better. For Wray, a cultivar that can grow to heading in the Tohoku region, the stem dry weight was greater by seeding in early June. For cultivars such as Wray with a sufficient growing period in a given region, the optimum seeding time to obtain stable higher stem yield existed and the cultivars should be seeded when they could grow under good weather conditions at the critical time strongly influences growth.