پديد آورندگان :
زرقاني، هادي دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت , نظامي، احمد دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت , خواجه حسيني، محمد دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت , ايزدي دربندي، ابراهيم دانشگاه فردوسي مشهد - دانشكده كشاورزي - گروه زراعت
چكيده فارسي :
به منظور تعيين مناسب ترين دوره كنترل علف هاي هرز كنجد، آزمايشي به صورت اسپليت پلات در قالب طرح بلوك كامل تصادفي در سه تكرار در سال ۱۳۸۷ در مزرعه تحقيقاتي دانشكده كشاورزي دانشگاه فردوسي مشهد انجام شد. تيمارهاي آزمايش شامل ژنوتيپ هاي كنجد (توده بومي كلات و رقم اصلاح شده اولتان) به عنوان فاكتور اصلي و دوره هاي عاري از علفهاي هرز (۲۰، ۳۰، ۴۰، ۵۵ و ۷۰ روز پس از سبز شدن) و تداخل با علف هاي هرز (۲۰، ۳۰، ۴۰، ۵۵ و ۷۰ روز پس از سبز شدن) به همراه دو تيمار رقابت و كنترل تمام فصل علف هاي هرز به عنوان فاكتور فرعي بودند. جهت تعيين دوره بحراني كنترل، از توابع گامپرتز و لجستيك استفاده شد. نتايج نشان دادند كه در اوايل فصل رشد خرفه و پيچك صحرايي و در اواخر فصل رشد تاج خروس، سلمه و سوروف علفهاي هرز غالب بودند. در تيمارهاي عاري از علف هرز تا ۴۴ روز پس از سبز شدن وزن خشك علف هاي هرز، به طور متوسط تا ۸۵ درصد نسبت به شاهد در رقابت تمام فصل كاهش يافت. با افزايش دوره تداخل علف هاي هرز در اول و آخر فصل، عملكرد اقتصادي كاهش يافت و با طولاني شدن دوره وجين بر عملكرد اقتصادي افزوده شد. با اين وجود، با افزايش طول دوره و جين در اوايل فصل رشد و يا در طي دوره كامل رشد كنجد، از وزن علفهاي هرز كاسته شد در حاليكه با كاهش طول دوره وجين در اواخر فصل رشد و يا عدم وجين در طي دوره كامل رشد كنجد، وزن خشك علفهاي هرز زياد شد. بر اساس نتايج اين آزمايش دوره بحراني كنترل علفهاي با احتساب ۵ و ۱۰ درصد كاهش عملكرد به ترتيب ۲۷ تا ۴۸ و ۳۰ تا ۴۰ روز پس از سبز شدن براي توده بومي كلات و ۲۲ تا ۷۲ و ۳۴ تا ۵۸ روز پس از سبز شدن براي رقم اصلاح شده اولتان برآورد شد.
چكيده لاتين :
Introduction: In order to improve the efficiency of weed management and reducing herbicide application,
determining the most sensitive weed-crop competition period is very important. There is a special period in
plant life cycle, that if the crop is kept free of weeds, yield reduction has not significant economically and also
weed control after that will not affect crop yield improvement. This period is known as the critical period
competition affected by climate, weed species dominance, field management methods and crop type and their
cultivars. Sesame is one of the important crops due to its high oil quality. This low input crop is very
considerable in terms of economic in arid and semi-arid subsistence farming area. Despite the importance and
antiquity of sesame cultivation in Iran, there is low information about the effects of weed on its growth and yield
and also critical period of weed competition. So, the present study was carried out to determine the critical
period of weed in two Common genotypes of sesame (Oltan cultivar and kalat Landrace) in Khorasan Razavi
province.
Material and Methods: This study was conducted at Research Farm of College of Agriculture, Ferdowsi
University of Mashhad with 36º 15' N latitude and 59º 28' E longitude and 985 m above the sea level, during
2009 growing season, Mashhad, Iran. The experiment was carried out as split plot based on the randomized
complete block design with three replications. Treatments were sesame genotypes (Olten cultivar and Kalat
landrace) as main plot and weed-free periods (20, 30, 40, 55 and 70 days after emergence (DAE)) and weed
interference -periods (20, 30, 40, 55 and 70 DAE) with two full season weed control and full season weed
competition, were considered as sub plots. Sampling from weeds was conducted before weeding and before the
end of sesame growing season in interference and weed free treatments, respectively. Sesame plants harvested at
physiological maturity stage, after eliminating the border effect area, from six m-2 and after drying in natural
condition, sesame seed yield was reordered. To determine the critical period of weed, non-linear regression was
used by fitting the data to Logistic and Compertz models. MSTAT-C software also was applied for analysis of
variance and means comparison.
Results and Discussion: Results showed that, the highest weed density was
recorded in weed interference conditions 30 days after sesame emergence and reduced after that. The dominant
weeds were Portulaca oleraceae, Convolvolus arvensis, Amaranthus retroflexus, Chenopodium album and
Echinochloa crus-galli. Weed dry weight was decreased on average by 85 percent in weed free treatments up to
44 days after emergence compared to full season weed interference control treatment. Sesame yield was
decreased with increasing the weed interference periods, but it was increased with increasing weed free period
treatments. Weed dry weight decreased significantly by increasing weeding duration. It was estimated that the
critical period of weed control in Kalat landrace were 27-48 and 30-40 days after emergence with considering 5
% and 10 % acceptable yield losses, respectively, while in Oltan cultivar were 22-72 and 34-58 days after
emergence, respectively. So the critical period of weed control in Kalat landrace was shorter than Oltan cultivar.
It seems that in kalat genotype once weeding during its critical period of weed control is enough, while it is
necessary at least twice in oltane cultivar. Short critical period of weed control in kalat landrace sesame may be
due to its shorter growing season and its faster canopy closure than Oltan cultivar.
