Grain growth and yield performance of wheat under subtropical conditions: I. Effect of sowing dates

The optimum sowing time of wheat in subtropical countries like Bangladesh l ies between mid-November to mid-December. Wheat is usually sown after trans planted summer rice (aman rice). Due to various reasons summer rice croppin g is frequently delayed and so is the wheat. Consequently, farmers are depr ived of harvesting potential yield of wheat. However, Kanchan, a high yield ing variety (HYV), performs relatively better at late sown conditions than other available wheat varieties. The aim of this study was to elucidate the agronomic reasons for better performance of Kanchan over other varieties. Kanchan ('late variety') and Akbar (a HYV and extensively cultivated) were sown in the field on December 04, 1995 and January 04, 1996. Their grain gr owth pattern from anthesis till maturity, and yield and yield components we re analyzed. Variety Kanchan outperformed Akbar in terms of number of ear b earing tillers/m(2), individual grain weight and finally grain yield under both sowing conditions. Grain yield was greatly reduced by sowing dates and December sowing plants produced 47% higher yield over the late sowing plan ts. Grain growth rate and duration for grain growth were affected seriously by sowing times. For December sowing plants the grain growth continued for 39 days in Kanchan and 35 days in Akbar, while the duration was reduced dr astically with late sowing to less than 21 days for Kanchan and 19 days for Akbar. Grain growth rate was also higher in Kanchan than in Akbar. Grain g rowth pattern indicates that both higher growth rate and longer growth dura tion in Kanchan are responsible for its higher grain yield under late sowin g conditions.