Growth and yield responses of sorghum (Sorghum bicolor [L.] Moench) varieties to sowing time in a rainforest zone of Nigeria

Sorghum is an important staple and commodity crop for West Africa, however, its production rarely meet demand. Due to its importance, efforts should focus on extension of sorghum production frontiers beyond the current ecological boundaries (the savannas of West Africa). Field experiments were conducted to evaluate the influence of sowing date on the performance of sorghum varieties in a rainforest zone of Nigeria. Sowing dates were: 15th July, 2nd and 20th August and 5th September, 2017 and 18th July, 5th and 17th August and 7th September, 2018 while sorghum varieties were Improved Deko, CSR-01, SK5912, 121 CKSV-180 and SAMSORG 17. Sowing dates were coded: SD1 (Mid July), SD2 (early August), and SD3 (mid August) and SD4 (early September) for each year experiment (2017 and 2018). Sowing dates differed in growing season lengths and weather conditions. Early maturing varieties (121 CKSV-180, CSR-01 and SAMSORG 17) gave highest yield gain for mid August and early September sowing dates while the late maturing varieties (SK 5912 and Improved Deko) gave highest grain yields for mid July, early and mid August sowing dates. SAMSORG 17 and Improved Deko produced heaviest grain yields and CSR-01, SK5912 the lowest. Early and mid August (SD2 and SD3) dates are the best sowing dates and SAMSORG 17 and Improved Deko are the best varieties in the rainforest zone of Nigeria. The study highlighted the relevance of sowing date and cultivar choice as location-specific management strategy for sustainable sorghum production in the rainforest zone of southern Nigeria.