ارزیابی برخی صفات کمّی ارقام گندم نان(Triticum Aestivum L.) در تاریخ‌های مختلف کاشت

تاریخ کاشت ارقام مختلف گندم (triticum aestivum l.) یکی از عوامل زراعی تعیین‌ کننده عملکرد بهینه در هر منطقه است. این تحقیق به‌‌منظور بررسی اثر تاریخ کاشت بر برخی صفات کمّی هشت رقم گندم نان به‌مدت دو سال زراعی (96-1394) در مزرعه تحقیقاتی موسسه تحقیقات اصلاح، تهیه نهال و بذر در کرج به‌اجرا درآمد. هشت رقم گندم نان شامل بهاران، سیوند، سیروان، مهرگان، چمران 2، حیدری، زارع و پیشگام در چهار تاریخ کاشت 20 مهر، پنج آبان، 20 آبان و پنج آذر به‌صورت کرت های خرد شده در قالب طرح بلوک‌های کامل تصادفی با سه تکرار مورد مطالعه قرار گرفتند. نتایج نشان داد که اثر تاریخ کاشت بر عملکرد دانه، عملکرد بیولوژیک، تعداد دانه در سنبله، تعداد سنبله در مترمربع و شاخص برداشت معنی‌دار بود. به‌طوری‌که تاریخ کاشت 20 مهر بالاترین عملکرد را داشت. اثر متقابل تاریخ کاشت و رقم بر عملکرد دانه و بیولوژیک، همچنین برخی از اجزای عملکرد معنی‌دار بود. بیشترین و کمترین عملکرد دانه به‌ترتیب برای رقم حیدری در تاریخ کاشت 20 مهر با مقدار 9529 کیلوگرم در هکتار و رقم چمران در تاریخ کاشت 5 آذر با مقدار 5474 کیلوگرم در هکتار به‌دست آمد. همچنین تاخیر در کاشت نسبت به تاریخ کاشت 20مهر، منجر به کاهش عملکرد دانه بین 16 تا 36 درصد گردید. اثرات متقابل تاریخ کاشت و رقم بر طول مراحل پنجه زنی، ساقه دهی، گل‌دهی و رسیدگی فیزیولوژیکی معنی دار بود. به نظر می رسد که تاریخ کاشت 20 مهر به‌دلیل بهره‌گیری بهتر از شرایط محیطی که شامل  دمای مطلوب‌تر، طولانی‌تر بودن فصل رشد، محتوای رطوبتی بیشتر خاک و استقرار مناسب گیاه است، بهترین تاریخ کاشت در منطقه مورد مطالعه باشد. امّا در شرایط محدودیت از نظر زمان کشت محصول در تاریخ کاشت های پنج آبان لغایت پنج آذر ارقام مهرگان و سیوند توصیه می شود تا کمترین میزان افت محصول به‌واسطه عدم کشت گیاه در زمان مناسب به‌وجود آید.

Evaluation of Quantitative Traits of Bread Wheat (Triticum aestivum L.) Cultivars in Different Planting Dates

Introduction Besides its commercial importance in the global wheat market, bread wheat (Triticum aestivum) is an efficient weapon in political and international relations. Its practical importance is increasing by the day. The planting date is an essential factor in crop production because meteorological parameters vary with the planting date changes. Singly or in combination, temperature, sunlight, and other meteorological factors influence plant growth and production. Planting date controls plant phenological total biomass production and influences the efficient conversion of biomass into economic yield (Khichar and Niwas, 2006). The purpose of determining planting date is to find the right time for a cultivar or a group of similar plant cultivars so that the set of environmental factors are suitable for seed germination and seedling establishment survival (Hore et al., 2002). It seems that planting various wheat cultivars by considering the high importance of wheat with different growth habits is necessary for agricultural experts and farmers to observe the different cultivars’ responses to various planting dates and weather conditions. Various cultivars, each compatible with weather conditions in a specific part of the country, were selected for this experiment. This experiment intended to determine how cultivars responded to each planting date by taking its yield potential and temperature changes into account, identifying the optimum planting date for each cultivar, and introducing the suitable cultivar in the late planting date.   Materials and Methods The splitplot experiment was conducted based on a complete randomized block design with three replications on the research farm of the Seed and Plant Improvement Research Institute in Karaj in two years (20152017). The bread wheat cultivars Baharan, Sivand, Sirvan, Mehregan, Chamran 2, Heidari, Zare, and Pishgam, formed the main plot factor and the various planting dates (12 October, 27 October, 11 November, and 26 November) the subplot factor. Yield and yield components such as the number of fertile spike per m2, number of grain per spike, number of grain per m2, 1000kernel weight were measured at the end of the growing season to evaluate responses of the cultivars to the various planting dates. Also, the phenological stage was recorded during the growing season.   Results and Discussion Results indicated that planting dates had significant effects on grain yield, biological yield, number of seeds per spike, number of spikes per m2, and harvest index. The highest yield was 12 November among the planting dates, and the Sivand cultivar had the highest grain yield (7708 kg.ha1). The interaction effects of planting date and cultivar were significant on grain yield, biological yield, and some yield components. The highest grain yield (9529 kg.ha1) was observed in the Heidari cultivar planted on 12 October and the lowest (5474 kg.ha1) in the Chamran cultivar planted on 26 November. Delays in planting reduced grain yield by 1636% compared to the most suitable planting date (12 October) because of the reduced vegetative and grainfilling periods.   Conclusion The highest grain yield at each of the planting dates was achieved for one of the cultivars. Therefore, the cultivars adapted to different climates exhibited their highest yields at different planting dates. Based on results, it is recommended that the Heidari and/or Sirvan cultivars be planted in Karaj and regions with climates to Karaj on 12th October.  In cases of limitations concerning planting dates (unfavorable weather conditions, insufficient planting equipment, etc.), the recommended dates for planting the Mehregan and Sivand cultivars are from 27 October to 26 November to minimize yield loss caused. It seems that 12 October is the best planting time for the study region because it allows better use of the environmental conditions, including more desirable temperature, more extended growing season, higher soil moisture content, and suitable seedling establishment.