The Effect of Nitrogen on Yield and Yield Components of Different Sesame (Sesamum Indicum L.) Varieties under Weed Competition

Competition, as one of the key issues and complex phenomena, is in the ecophysiological discussions of plant communities and is influenced by many factors that can be attributed to weed interference with the crop and the use of fertilizer inputs. Considering that nowadays the use of plant oils and sesame cultivation has increased, the aim of this study was to investigate the response of sesame cultivars to nitrogen increase in competition with weeds to identify the limitations and benefits of nitrogen use.
 
  The experiment was conducted as a split factorial based on randomized complete block design with three replications at Omidieh (Khuzestan Province) during the summer of 2013. The main plot consisted of nitrogen fertilizer application levels (control [non-use] and use of 50 and 100 kg/ha nitrogen from urea form) and subplots were in a factorial combination of sesame varieties (Behbahan landrace, Yellow-white, tn-238, and tn-240) and weed competition in two levels (weed free and weed infest). In this experiment, morphological traits, harvest index, yield, and yield components of sesame were measured.
  The results showed that the effect of different amounts of nitrogen, weed competition, and sesame varieties on yield and yield components were significant. The interaction effects of nitrogen and sesame varieties on the leaf area index, number of capsules per plant, 1000-grain weight, and harvest index of sesame were significant. Increasing nitrogen improved LAI but weed interference reduced the number of capsules per plant by 23 percent. The effect of weed on 1000 grain weight showed that weed competition decreased this trait by 7.5 percent. The effects of nitrogen, cultivar, and weed competition on grain and biological yield were significant, so that the highest grain yield (158.06 gm-2) belonged to the 100 kg N treatment and between different varieties of sesame obtained from the Behbahan local variety(151.38 gm-2). Compared to the control (no nitrogen) the highest level of nitrogen treatment increased 31 percent in biological yield. In weed-free conditions, the Biological yield was more than the weed-infested treatment, so that the weed control increased the biological yield by 24 percent.
  The results of this study showed that the cultivation of Behbahan local variety with the application of 100 kg N, under Omidieh regional conditions, has been Improved many traits of sesame, including plant height, leaf area index, number of capsules per plant, and 1000 grain weight that this improvement was due to the get maximum yield.