Evaluation of the effect of sowing date and nitrogen fertilizer on yield and yield components of Camelina (Camelina sativa L.) under dryland condition

Extended Abstract
Introduction
The production of adequate food is an essential national and security objective for every country. Achieving this goal requires adopting appropriate measures such as increasing the efficiency of agricultural production systems through suitable policies, utilizing new varieties adapted to current conditions, and utilizing unconventional water resources. Camelina, a new oilseed crop, has unique agricultural properties such as low nutrient requirements, resistant to weeds, high resistance to drought stress, pests, and plant diseases. The provision of environmental factors within the range of the plant's tolerance and resilience plays a crucial role in achieving desirable and suitable yield of any plant. Nitrogen is among the vital nutrients that significantly affect crop yield that its deficiency can lead to severe reduction in yield and excess of it also poses significant environmental risks. Sowing date is another environmental factor that affects agricultural production. By sowing each crop at the desired time, better utilization of other effective environmental factors on the seedyield can be achieved. Hence, this study aimed to evaluate the effects of sowing date and nitrogen fertilizer application on the yield, yield components, and oil production of Camelina as a new agricultural crop, considering the importance of self-sufficiency in oil production for the country and efficient use of agricultural lands indryland condition.
Materials & Methods
This experiment was conducted as split plot layoaut based on a complete randomized block design with three replications at the research farm of Razi University of Kermanshah during the agricultural in 2018-2019. The main factor was sowing date (October 25, November 9 and November 21), and the sub-factor was nitrogen fertilizer (including0, 50, 100, 150 kg ha-1). The evaluated traits included recording plant growth stages, seedyield, yield components, and oil production. The sowing dates were determined based on effective rainfall and the source of nitrogen supply was also 46% urea fertilizer. The fertilization process was carried out three times, including at the end of the four-leaf stage, at the end of the stem elongation stage, and at the beginning of the grain filling stage. The studied traits included yield and its components, total dry weight yield, harvest index, and grain oil yield. The data were analyzed using ANOVA and the means were compared with the Duncan test.
Results & Discussion
The study findings indicated that the shortest growth period was observed for the sowing date of November 9, whereas the growth period increased in other sowing dates. Notably, the highest seed yield (459 kgha-1) was obtained from sowing ofNovember 9, while the highest number of pods per plant (52.8% increase) was belonged to the sowing date of October 25. Except for growth stages, other traits were also significantly affected by the amount of nitrogen fertilizer. Our findings demonstrated that the treatment with maximum nitrogen fertilizer application led to the highest seed yield, total dry weight yield, and oil yield of camelina, which were 37.4%, 31.4%, and 16.5% greater than the control (without fertilizer), respectively. It appears that desirable sowing dates lead to an improvement in yield-related traits and its components due to the plant's greater utilization of environmental conditions and minimizing exposure to high temperatures during the final stages of growth. High temperatures at the end of the growing season can cause physiological limitations, especially during the flowering period, and subsequently lead to limitations in the supply of photosynthetic assimilates and weak plant growth (Moravveji et al., 2017). Various studies have shown that nitrogen fertilizer also improves grain yield components such as the number of seeds per pod, and number of sub and sub sub branches, and 1000-grain weight, ultimately leading to improved grain yield and oil yield (Manore & Yohanns, 2019), which is consistent with the results of this study.
Conclusion
It can be concluded that in dry conditions where the sowing date depends on seasonal rainfall, a specific sowing date cannot be determined with certainty.