Evaluation of Crop Production of Canola (Brassica napus L.) Cultivars Due to Irrigation Cut-off and Different Planting Dates in Karaj Climatic Conditions

The response of different canola varieties to irrigation cut-off and changes in planting dates depends on various factors such as climatic conditions, soil type, and specific characteristics of the varieties and growth stages of the plants. Each canola variety may react differently to variations in water and shifts in planting dates. To investigate the effects of irrigation cut-off and planting date on the seed yield and its components of rapeseed cultivars current research was done. This study was conducted as factorial split plot experiment based on randomized complete block design (RCBD) with three replications. The main plots were assigned to irrigation treatments [including regular irrigation (where irrigation was applied after 80 mm of evaporation from Class A pan) and irrigation cut-off from silique formation stage onwards]. The sub-plots were assigned to different planting dates, including September 27 and October 27 and four winter rapeseed cultivars (Tassilo, Elvise, Neptune and Okapi) were evaluated in a factorial arrangement in sub-plots. Both irrigation cut-off and delayed planting date had a significant impact on various growth and yield-related traits in rapeseed cultivars. Reduced plant height, fewer sub-branches per plant, fewer siliques per plant, fewer seeds per pod and lower 1000-seed weight. Also, different rapeseed cultivars that were studied exhibited significant variations in all evaluated traits. Among the cultivars, Elvise and Neptune stood out as they achieved the highest seed yields. Under normal irrigation conditions, Elvise yielded 3346 kg.ha-1, while Neptune produced 3220 kg.ha-1. Even under irrigation cut-off conditions, these cultivars still demonstrated promising performance, with Elvise yielding an average of 3211 kg.ha-1 and Neptune yielding 3081 kg.ha-1. This advantage in seed yield was primarily attributed to an increase in the sink capacity of the yield components. As a result, Elvise and Neptune cultivars can be recommended as suitable choices for rapeseed production, as they have shown not only high seed yields under normal irrigation conditions but also stable production capabilities even under water stress conditions after pod formation.