تأثير روش‏هاي مختلف كشت پياز خوراكي (Allium cepa L.) و ميزان نيتروژن بر روند رشدي آن در شرايط تداخل با اويارسلام ارغواني (Cyperus rotundus)

Effect of Different Planting Methods of Onion (Allium cepa L.) and Nitrogen Rate on Onion Growth Pattern under Interference with Purple Nutsedge (Cyperus rotundus)

به منظور بررسی اثر روش كشت پیاز خوراكی و میزان نیتروژن بر روند رشد آن در شرایط تداخل با اویارسلام ارغوانی، آزمایشی در سال 1392 در گلخانه تحقیقاتی دانشكده كشاورزی دانشگاه بیرجند به‌صورت فاكتوریل در قالب طرح بلوك كامل تصادفی در سه تكرار اجرا شد. فاكتور اول شامل سه روش كاشت پیاز خوراكی (بذر، سوخچه و نشاء) و فاكتور دوم شامل سه سطح مختلف نیتروژن (50، 100 و 150 كیلوگرم نیتروژن خالص در هكتار) بود. تیمار سطوح نیتروژن اثر معنی داری بر روی ارتفاع، شاخص سطح برگ، وزن خشك اندام هوایی و وزن خشك پیاز داشت. تیمار روش كاشت نیز دارای اثر معنی داری بر ارتفاع، تعداد برگ، شاخص سطح برگ، وزن خشك اندام هوایی و وزن خشك پیاز بود. همچنین اثر متقابل نوع روش كاشت و سطوح نیتروژن دارای اثر معنی دار بر روی ارتفاع، شاخص سطح برگ و وزن خشك اندام هوایی بود اما بر تعداد برگ و وزن خشك پیاز مؤثر نبود. بررسی روند رشدی پیاز در طی فصل رشد در شرایط تداخل با علف هرز اویارسلام ارغوانی نشان داد كه بیشترین و كمترین میزان رشد پیاز به‌ترتیب مربوط به روش سوخچه و بذر بود. همچنین تغییرات خصوصیات رشدی پیاز تحت سطوح مختلف كود نیتروژن در شرایط رقابت نشان داد كه حداكثر میزان رشد پیاز در سطح 100 و حداقل آن در سطح 50 كیلوگرم نیتروژن خالص حاصل شد. براساس نتایج تحقیق حاضر، می توان مقدار 100 كیلوگرم نیتروژن خالص و روش كشت سوخچه را به‌عنوان مناسب ترین تیمار مدیریتی در مزارع پیاز آلوده به اویارسلام توصیه نمود.

<strong >Introduction </strong > Human always has looked for improving food production through increasing crops yield. In this path, weeds through competition with crop for environmental factors and inputs have reduced the quantity and quality of crop products. Competition for nitrogen absorption not only is the most common form of intra-specific competition amongst crop plants, but also is the most popular form of inter-specific competition in the system of weed-crop interference. Therefore, understanding the method of nitrogen absorption and its allocation in competing plants, will be a key tool to improve weed management strategies. <strong >Materials and Methods </strong > In order to study the effect of sowing method and nitrogen rate on the growth pattern of onion under interference with purple nutsedge, a factorial experiment based on a randomized complete block design was conducted with three replications at the Research Greenhouse of University of Birjand in 2013. The first factor included three sowing methods of onion (seed sowing, onion set and transplanting) and the second factor consisted of three levels of nitrogen (50, 100 and 150 kg N ha-1, equivalent of 25, 50 and 75 mg N kg-1 soil) that urea fertilizer with a purity of 46% was used for this purpose. <strong >Results and Discussion </strong > The results of the analysis of variance showed that nitrogen levels had significant effects on plant height, leaf area index as well as aboveground and bulb dry weights. Furthermore, sowing methods revealed significant effects on plant height, leaf number, leaf area index as well as aboveground and bulb dry weights. Moreover, the interaction between sowing methods and levels of nitrogen had a significant effect on plant height, leaf area index and aboveground dry weight, while it had no significant effect on leaf number and bulb dry weight. The results of the comparisons of the means of onion planting methods and nitrogen levels interactions confirmed that the superiority of the influence of onion set were planted method and high level of nitrogen in plant height trait, so that the maximum plant height was obtained where onion set methods and high nitrogen levels were applied during the growing season. In addition, the lowest plant height during the growing season was observed where the direct seed sowing method and 150 kg N ha-1 were used. The lowest leaf number during the growing season were obtained from direct seed sowing method and the leaf number per plant in this method of planting was 4.33 and 4.66 at eight and ten weeks after planting, respectively. The greatest number of onion leaves was produced in onion set planting method and the leaf number per plant in this method was 12.66 and 13.44 at eight and ten weeks after planting, respectively. The highest leaf area index of onion plants during the growing season was observed under onion set planting method and high levels of nitrogen, while the lowest value of this trait was obtained from direct seed planting method. During the growing season, the maximum shoot dry weight of onions was observed where the onion set planting method and high levels of nitrogen were employed. At eight and ten weeks after planting, the maximum amount of this trait was obtained from 100 kg N ha-1 that was about 4.335 and 5.565 gr plant1, respectively. <strong >Conclusions </strong > Onion growth pattern under interfering with purple nutsedge demonstrated that the highest and lowest growth of onion plants were obtained where onion sets and seed sowing planting methods were employed, respectively. Moreover, changes of growth characteristics of onion under different levels of nitrogen fertilizer and interference conditions illustrated that the maximum and minimum amount of onions growth were obtained at 100 and 50 kg N ha-1, respectively. In conclusion, the superiority of applying the onion set planting method and 100 kg N ha-1 improved onion growth where it competes with purple nutsedge. Thus, in order to minimize the yield damage due to purple nutsedge presence, application of 100 kg N ha-1 and using the onion set planting method can be recommended as the most appropriate treatment in the management of infected farms with purple nutsedge. However, this study was conducted under greenhouse conditions and there is no doubt that the study should be repeated in the field to verify these results.