Impact of sowing dates on the growth and straw yield of some bread wheat cultivars and their relationship with accumulated heat units

الملخص

An experiment was conducted at Research Station, State Board for Seeds Testing and Certification, Baghdad, Iraq during 2015/2016 season to determine the effect of  four sowing dates (20^th October, 10^th November, 30^th November and 20^th December) on growth and straw yield of three wheat cultivars (Bohooth-22, Bohooth-158, and Rasheed) and their relationship with accumulated heat units. Flag leaf area and biological yield decreased with late sowing dates. Highest values of flag leaf area (62.17 cm²), number of tillers m^-2 (375.8), biological yield (15.12 t ha^-1) and straw yield (14.47 t ha^-1) were obtained on 20^th October. Cultivars responded differently to the four sowing dates. Highest values of phenology (DAS) (177.3 days) and growing degree days (GDD) (2607.2 ⁰C) were obtained at maturity stage with sowing date 20^th October. Highest value for phenothermal index (PTI) was obtained during the period from sowing to seedling growth stage with sowing date 20^th October (23.6). Bohooth-22 gave highest values regarding DAS and GDD during the first period (from sowing to seedling growth stage), while Rasheed gave highest values during the rest periods. Highest and lowest values of PTI were recorded with Bohooth-158 (14.8 and 11.8) during the period from sowing to seedling growth, respectively.

DOI = 10.24897/acn.64.68.34