پديد آورندگان :
هاشمي، ثمانه دانشگاه فردوسي مشهد - دانشكده كشاورزي - اكولوژي گياهان زراعي , زعفريان، فائزه دانشگاه فردوسي مشهد - دانشكده كشاورزي - اكولوژي گياهان زراعي , فرهمند فر، اسفنديار دانشگاه فردوسي مشهد - دانشكده كشاورزي - اكولوژي گياهان زراعي , باقري شيروان، ميلاد دانشگاه فردوسي مشهد - دانشكده كشاورزي - اكولوژي گياهان زراعي
كليدواژه :
خلر و ساختار كانوپي , شبدر ايراني و ماشك , گياهان پوششي , علف هاي هرز
چكيده فارسي :
به منظور مطالعه تغييرات عمودي سطح برگ و ماده خشك كانوپي سويا (Glycine max L.) در رقابت با علف‌هاي‌هرز و در حضور گياهان پوششي، آزمايشي در مزرعه تحقيقاتي دانشگاه علوم كشاورزي و منابع طبيعي ساري در سال 1392 به صورت بلوك كامل تصادفي با سه تكرار اجرا شد. تيمار‌هاي آزمايشي شامل گياهان پوششي (شبدر ايراني (Trifolium resupinatum L.)، شنبليله (Trigonella foenum–graecum L.) ، خلر (Lathyrus sativus L.) و ماشك (Vicia sativa L.)) و زمان‌هاي كاشت گياهان پوششي (همزمان با سويا و سه هفته بعد از كاشت سويا) بوده و همچنين دو تيمار شاهد به صورت تك كشتي سويا با و بدون وجين در نظر گرفته شد. نتايج نشان داد حداكثر ميزان شاخص سطح برگ و تجمع ماده خشك سويا در لايه‌هاي مختلف كانوپي بسته به نوع گياه پوششي و زمان كاشت آن متفاوت بود در حالي كه گياهان پوششي در كاشت با تأخير شاخص سطح برگ و ماده خشك كمتري نسبت به كاشت همزمان داشتند. در اكثر موارد بيشترين شاخص سطح برگ و همچنين تجمع ماده خشك علف‌هاي‌هرز در لايه ابتدايي كانوپي (20-0 سانتي متر) به دست آمد. بيشترين مجموع سطح برگ علف¬هرز در تيمار كاشت همزمان سويا با شنبليله (4/290 سانتي متر مربع) و بيشترين ماده خشك مجموع علف‌هرز در تيمار كاشت سوياي بدون وجين (4 / 12 گرم بر بوته) مشاهده شد، در حالي كه كمترين مجموع سطح برگ و ماده خشك كل علف‌هرز (به ترتيب صفر سانتي¬متر مربع و صفر گرم بر بوته) در تيمار كاشت با تأخير ماشك به دست آمد، همچنين كاشت با تأخير ماشك موجب توليد بيشترين عملكرد دانه سويا ( 6 / 3792 كيلوگرم در هكتار) در شرايط حضور علف‌هرز شد كه بيشترين توانايي سركوب كنندگي رشد علف‌هاي‌هرز را نسبت به ساير گياهان پوششي داشته است. به نظر مي رسد كاشت ماشك گل خوشه اي 21 روز بعد از سويا براي سركوب كردن علف هاي‌هرز جايگزين مناسبي در كشاورزي پايدار باشد.
چكيده لاتين :
Introduction
Amount and vertical distribution of leaf area are essential for estimating interception and utilization of solar
radiation of crop canopies and, consequently dry matter accumulation (Valentinuz & Tollenaar, 2006). Vertical
distribution of leaf area is leaf areas per horizontal layers, based on height (Boedhram et al., 2001). Aboveground
biomass is one of the central traits in functional plant ecology and growth analysis. It is a key parameter
in many allometric relationships (Niklas & Enquist, 2002). The vertical biomass distribution is considered to be
the main determinant of competitive strength in plant species. The presence of weeds intensifies competition for
light, with the effect being determined by plant height, position of the branches, and location of the maximum
leaf area. So, this experiment was conducted to study the vertical distribution of leaf area and dry matter of
soybean canopy in competition with weeds and cover crops.
Materials and methods
This experiment was performed based on complete randomized block design with 3 replications in center of
Agriculture of Joybar in 2013. Soybean was considered as main crop and soybean and Persian clover (Trifolium
resupinatum L.), fenugreek (Trigonella foenum–graecum L.), chickling pea (Lathyrus sativus L.) and winter
vetch (Vicia sativa L.) were the cover crops. Treatments were included cover crops (Persian clover, fenugreek,
chickling pea and winter vetch) and cover crop planting times (simultaneous planting of soybean with cover
crops and planting cover crops three weeks after planting of soybeans) and also monoculture of soybeans both
in weedy and weed free conditions were considered as controls. Soybean planted in 50 cm row spacing with 5
cm between plants in the same row. Each plot was included 5 rows soybeans. Cover crop inter-seeded
simultaneously in the main crop. Crops were planted on 19 May 2013 for simultaneous planting of soybean. The
dominant weed species were green foxtail (Setaria viridis L.), foxtail grass (Alopecurus myosuroides Huds), and
red root pigweed (Amaranthus retroflexus L.) in the experimental field. The other weed was considered as the
others. At the soybean canopy closure stage, a vertical card board frame marked in 20-cm increments was used
in the field as a guide to cut standing plants including soybean, cover crops and weeds. In each vertical layer of
canopy, leaves and stem samples were separated. The leaf area both crops and weeds were measured with a leaf
area meter LICOR-3000A (LI-COR, Lincoln, NE, USA). Stem and leaf samples oven dried.
Results and discussion
The results showed that the maximum leaf area and dry matter of soybean was varied in different layers of
canopy depending on the type of cover crop and cover crop planting time, while delaying in planting of cover
crop causes lower leaf area and dry matter than the plants were planted at the same time with soybean. In most
cases, the maximum leaf area index and dry matter accumulation of weeds were obtained in primary layer (0-20
cm). The maximum weed leaf area (290.4 cm2) was observed in simultaneous planting of soybean with
fenugreek and maximum of total weed dry matter (12.4 g.plant-1) was observed in soybean without weeding,
while the minimum of weed total leaf area and total weed dry matter (0 cm2 and 0 g.plant-1, respectively) was
achieved in planting of winter vetch after 21 days of soybean planting. Also delayed planting of winter vetch
produced the maximum grain yield (3792.6 kg.ha-1) of soybean in weedy plots, where it had the greatest weed Conclusion
Winter vetch can suppress weed with competition and allelopathic mechanism, so we can conclude that
winter vetch planting21 days after soybean planting is suitable replacement for weed suppression in sustainable
agriculture.
