چكيده فارسي :
نیتروژن پس از آب دومین عامل محدودكننده رشد گیاهان در شرایط دیم بشمار می‌آید، لذا برای تولید اقتصادی جو در این مناطق، استفاده مناسب از آنبسیار ضروری است. به‌منظور ارزیابی پاسخ ژنوتیپ‌های جو دیم به مصرف نیتروژن، پژوهشی در قالب طرح بلوك‌های كامل تصادفی به صورت كرت‌های دوبار خردشده با زمان مصرف نیتروژن در كرت‌های اصلی (كل نیتروژن درپائیز، در پائیز + در بهار و در پائیز + در بهار)، مقادیر نیتروژن (صفر، 30، 60، 90 و 120 كیلوگرم در هكتار) در كرت‌های فرعی و ژنوتیپ‌های جو (سهند، آبیدر، Dayton/Ranny، Alpha/Gumhuriyet/Sonja و B-C-74-2) در كرت‌های فرعی در فرعی در 4 بلوك و به مدت 3 سال زراعی (89-86) در ایستگاه تحقیقات كشاورزی دیم به اجرا درآمد. نتایج نشان داد، مصرف نیتروژن از طریق افزایش معنی‌دار (01/0P≤) تعداد سنبله در واحد سطح (243-112) و ارتفاع بوته (6/17-3/6 سانتی‌متر) به عنوان سطح اندام‌های فتوسنتزكننده گیاه، طول (2/0-1 سانتی‌متر بر بوته) و وزن (2/0-1/0 گرم بر بوته) ریشه در مرحله پنجه‌زنی گیاه و كارایی استفاده از آب (5/2-3/1 كیلوگرم در هكتار بر میلی‌متر) باعث افزایش معنی‌دار عملكرد دانه، بیولوژیك و كاه (01/0P≤) شد. نیاز نیتروژنی جو در شرایط خشكسالی حدود 40 كیلوگرم در هكتار و در سال‌های نرمال 43 كیلوگرم در هكتار در منطقه مورد مطالعه تعیین شد كه این مقادیر به ترتیب برای دستیابی به عملكردهای دانه 1784 و 3100 كیلوگرم در هكتار می‌باشد. در سال‌های نرمال 30 كیلوگرم در هكتار آن در پائیز و 13 كیلوگرم در هكتار به صورت سرك همرا بارندگی‌های اوایل بهار مصرف می‌شود. در نهایت، اثر بارندگی در افزایش عملكرد دانه جو دیم 1/2 برابر بیشتر از مصرف نیتروژن بود و این موضوع اهمیت بیشتر آب را نسبت به نیتروژن در دیمزارهای ایران به اثبات می‌رساند.
چكيده لاتين :
Introduction: Nitrogen is the main component of fertilizer programs necessary for production of high quantity dryland barley. This element is the second limiting factor, after water in dryland areas. So for economic production of barley, the proper nitrogen fertilizer application is essential to increase seed quantity and quality in Iran dryland areas. Many researchers have been confirmed that dryland barley yield increased by nitrogen application management. Nitrogen fertilization in dryland areas can increase the use of soil moisture, and improve barley yields to some extent. Different studies have been confirmed interactions between water stress and nitrogen fertilizers on barley, especially under field conditions. From the nitrogen management factors, timing and amount of nitrogen application is known as the most important aspect. This project established in order to study nitrogen rates and nitrogen application time 's effects on nitrogen requirement, nitrogen agronomy use efficiency (NUE) and crop characteristics of various dryland barley genotypes in cold and semi cold drylands of Iran.
Materials and Methods: This study was carried out in split-split plot in a RCBD in Dryland Agricultural Research Institute (DARI), Maragheh; where nitrogen application times (fall, 1/2 in fall and 1/2 in spring and 2/3 in fall and 1/3 in spring) were assigned to the main plots, nitrogen rates to sub plot (0, 30, 60, 90 and 120 kg/ha), and 5 dryland barley genotypes to sub-sub plots (Sahand, Abidar, Dayton/Ranny, Alpha/ Gumhuriyet/ Sonja and B-C-74-2)in 4 replications during 2007-2010 years. The Rainfall were 177-498 mm.yr-1 (long term mean is 365 mm.yr-1) in cropping years in DARI station. Soil samples were collected from 0-25 cm for determining total N, P-Olsen, K-Ammonium acetate, TNV, OC, Soil texture, pH, EC and Fe, Mn, Zn and Cu-DTPA before sowing and collected from 0-2, 20-40 and 40-60 cm depths in sub-sub plots in shooting stage (GS32) for determining NO3− andNH4+. Ammonium measurement in the soil KCl extracts were down by spectrophotometry method and colorimetric reaction at 655 nm. Also, Absorption spectrophotometry method was used for determination of nitrate in soil extract based on its UV absorbance at 210 nm. In this method two measurements were carried out; one before (by Zn coated by Cu) and second after reduction of nitrate). Using the difference between these two measurements, concentration of nitrate in the extracts was determined.
Results and Discussion: The results showed that nitrogen application rates significantly increased (p <0.01) grain (597-1058 kg.ha-1), biological (1588-3631 kg.ha-1) and straw (990-2565 kg.ha-1) yields and relationship between nitrogen rates and grain yield was quadratic regression. Nitrogen application increased barley grain yield by increasing the of number of heads per m2 (112-243) as yield component and plant height (6.3-17.6 cm) as the photosynthetic organs, root length (0.2-1.0 cm.plant-1) and weight (0.1-0.2 g.plant-1) in tillering stage as nutrient and water uptake organs. There was not significant differences between studied genotypes from the view point of grain yield, but this characteristic significantly affected by timing the nitrogen application. The suitable nitrogen application time for dryland barley was split method. According to these results, rainfall use efficiency for control (without nitrogen application) and mean of nitrogen treatments was measured 5.4 and 7.5 kg.ha-1mm-1, respectively. Also comparison of precipitation and nitrogen application effects in increasing of dryland barley grain yield showed that the effect of rainfall more than twice nitrogen. Dryland barley nitrogen requirements were determined 40 kg N.ha-1 in drought years (no rainfall in spring) and 43 kg N.ha-1 in normal years. This rates is in order to achieve the 1784 and 3100 kg.ha-1 grain yield respectively. In normal years, 30 kg N.ha-1 applied at planting time in autumn and 13 kg N.ha-1 spring topdress application at the same time with early spring rains. Nitrogen agronomy use efficiency in the nitrogen requirement value was determined 18.3 kg.kg-1 and with increasing of each nitrogen unit, barley dryland grain yield was decreased 0.124 kg.ha-1. This decline continued until the last rate of nitrogen in a linear.
Conclusion: It can be concluded that the rates and timing of nitrogen application affected yield components, grain yield and nitrogen and water use efficiency in dryland barley genotypes and theses changes will be effective in improving seed quantity. The effect of rainfall in increasing grain yield of dryland barley was 2.1 times more than nitrogen fertilizer and this proved water is more important than nitrogen in the Iran dryland areas. However, nitrogen application of more than optimum rate increased water stress and decreased grain yield, but nitrogen optimal rate application is economically efficient to produce of dryland barley genotypes.
