Sesame (Sesamum indicum L.) Cultivars Yield Response to Nitrogen Rates Under Full and Deficit Irrigation

Evaluating the response of sesame cultivars to different irrigation and nitrogen treatments plays a pivotal role in the optimal use of resources and increasing production. Hence, an experiment was conducted in a randomized complete block design arranged in split-factorial with three replications in Karaj (Research Farms of Seed and Plant Improvement Institute) during 2017 and 2018. In this experiment, irrigation treatments at two levels, including deficit irrigation and full irrigation, were allocated to main plots, and different amounts of nitrogen (0, 60, and 120 kg N ha-1) and sesame cultivars (Oltan, Dashtestan 2 and Naz) were appointed to the sub-plots. The results indicated that in all cultivars, the effect of nitrogen on yield and yield components decreased due to water deficit conditions. However, the response of the Dashtestan 2 cultivar to nitrogen under water deficit conditions was better than two other cultivars. The results also showed that under deficit irrigation condition, only in Dashtestan 2, the application of more than 60 kg ha-1 nitrogen fertilizer is recommended to achieve maximum seed yield (595 kg ha-1), while under complete irrigation condition, in addition to Dashtestan 2 cultivar, seed yield in Oltan cultivar also showed a positive and significant response to nitrogen fertilizer application at a level above 60 kg ha-1 and the maximum seed yield in this cultivar (1138 kg ha-1) was obtained when 120 kg ha-1 nitrogen was applied. In contrast, even under complete irrigation conditions, nitrogen fertilizer application of more than 60 kg ha-1 did not significantly affect increasing see yield in Naz cultivar, which is not a recommended practice.