اثر رژيم‌هاي مختلف آبياري بر روي عملكرد و اجزاي عملكرد ارقام گندم (Triticum aestivum L.) در شرايط اقليمي رامين

Effect of different irrigation regimes on yield and yield components of wheat (Triticum aestivum L.) cultivars in Ramin climate

امروزه با افزايش روزافزون جمعيت و نياز به غذا و محدوديت منابع آب، افزايش عملكرد گياهان زراعي در واحد حجم آب مصرفي اهميت به‌سزايي دارد. محدوديت منابع آب با هدف افزايش توليد محصولات زراعي، اهميت دستيابي به ارقام متحمل به شرايط محيطي دشوار  با راندمان مصرف آب بالا را آشكار مي‌سازد. در اين راستا يك مطالعه مزرعه‌اي در خصوص اثر سطوح مختلف آبياري بر روي عملكرد و اجزاي عملكرد رقم‌هاي مختلف گندم طي سال‌هاي 9089 در منطقه تحقيقاتي زراعي دانشگاه كشاورزي و منابع طبيعي رامين خوزستان به اجرا درآمد. آزمايش به‌صورت كرت‌هاي  يك‌بار خردشده در قالب طرح بلوك كامل تصادفي با سه تكرار انجام شد.  تيمارها شامل 3 رقم گندم (چمران، افلاك و وريناك) و پنج سطح آبياري I1 (آبياري در مرحله 2برگي)، I2 (آبياري در مراحل 2برگي + پنجه‌زني)، I3 (آبياري در مراحل 2برگي + پنجه‌زني + آبستني)، I4 (آبياري در مراحل 2برگي + پنجه‌زني + آبستني + گل‌انگيزي) و I5 (آبياري در مراحل 2برگي + پنجه‌زني+ آبستني + گل‌انگيزي + شيري شدن دانه‌ها) بودند. رقم چمران به‌طور معني­داري بيشترين عملكرد دانه (4822/5 كيلوگرم در هكتار) در مقايسه با رقم  افلاك  و وريناك داشت. بعلاوه در بررسي كليه سطوح آبياري، نتايج نشان داد كه رقم چمران بيشترين عملكرد دانه را در مقايسه با دو رقم ديگر به خود اختصاص داد. در بين سطوح مختلف آبياري بيشترين و كمترين عملكرد به ترتيب در تيمار I5 وI2به دست آمد.به طور كليدر اين آزمايش مشاهده گرديد كه تنش رطوبتي خاك، عملكرد دانه گندم را از طريق كاهش وزن هزار دانه، تعداد پنجه در مترمربع و تعداد سنبلچه در سنبله در مترمربع كاهش مي‌دهد.بنابراين، عملكرد گندم در شرايط كمبود آب در هركدام از مراحل بحراني رشد كه اتفاق بيافتد كاهش عملكرد را به دنبال خواهد داشت.

Introduction Wheat (Triticum aestivum L.) is the most important cereal used as staple food in Iran. Despite higher yield wheat potential in Iran, average grain yield of wheat in Iran is much less than most of the wheat growing countries of the world (FAO., 2013). Nowadays increase of population and need for food and limitation of water for food and limitation of water resources have, increase yield in the volum e of water have a crucial inpact. Limitation of water resources in order to increasing tolerant Cultivars to severe conditions with high water use productivity. Earlier research showed that irrigation consistently increased wheat yield (Rahim et al., 2007). Wajid et al. (2002) reported that wheat yield by applying irrigation at all definable growth stages. Jamal et al. (1996) concluded that grain yield of different wheat cultivars were significantly reduced by water stress at all critical growth stages and greatest reduction was at anthesis stage. The present study was therefore undertaken to examine the yield response of wheat cultivars to different water irrigation in Ramin climate conditions.   Materials and methods In order to a field study pertaining to the effect of irrigation intervals on yield and yield components of wheat cultivars was conducted during 20112012 growing season at Agronomic Research Field of Ramin Agriculture and Natural Resources University of Khouzestan. Khouzestan Province is southwestern Iran, its covers and area 63633/6 km2 between lattitudes 29o33o N and longitudes 47o 40` 50o 33` E. The climate of the province is affected by weather systems from the Mediterranean and the Persian Gulf so that the weather is typically that of a semiarid/temperate climate. The experiment was laid out using RCBD with split plot arrangement. Treatment were three cultivars wheat (Chamran, Aflak and Verinak) which were kept in main plot and five irrigation intervals I1 (irrigation after two leaf stage), I2 (irrigation after two leaf stage + tillering stage), I3 (irrigation after two leaf stage + Tillering stage + booting stage), I4 (irrigation after two leaf stage + Tillering stage + booting stage + anthesis stage) and I5 (irrigation after two leaf stage + Tillering stage + bootingstage + anthesisstage + milking stage) that were placed in sub plots. Experiment was replicated thrice having plot size of 1.5m × 6m with six rows per plot. Half does of nitrogen and full does of phosphorus was applied during seed bed preparation while remaining half does of nitrogen was applied with first irrigation post emergency. Data on plant height, number of fertile tillers, number of spikelets per spike, number of fertile tillers, number of spikelets per spike, number of grains per spike, 1000grain weight, grain yield, straw yield and harvest index were recorded by using standard procedures. Data were analyzed statistically by using SAS analysis of variance technique and treatment means were compared by using least significant difference (LSD( test at 5% probability level (Steel and Torrie., 1984).   Results and discussion Chamran cultivar recorded highest grain yield (4822.5 kg ha1), number of tillers (335m2) and harvest index (45/33) which were significantly higher than the other two cultivars. Highest grain yield in Chamran cultivar might be due to the increase in number of tillers m2 (Sharif et al., 1999) and with higher 1000grain weight (Wajid et al., 2002). Howover minimum plant height (73cm) and number of spikelets spike1 (17) recorded at Chamran cultivar. Wheat crop supplied with five irrigations at irrigation after two leaf + Tillering + booting + anthesis + milking recorded the highest grain yield (5670.4 kg ha1) which was significantly higher than all the other intervals irrigation. Interaction between cultivars and irrigation levels was significant for grain yield. At I5, cultivars Chamran and Aflak increased yields (52.68% and 57.07%) over I1 which were statistically at par with each other.   Conclusions Finally, the results revealed that soil moisture stress causes low grain yield, by inducing low 1000grain weight, number of tillers m2. Thus, wheat, a staple food, appears to be suffering yield losses due to deficiency of irrigation water at any critical stage. Therefore, wheat grower must be careful about water stress on critical stage which can cause tremendous yield losses. It is also clear that there is a considerable span to exploit the yield potential of wheat cultivars in irrigation area of Iran.