بررسی تاثیر علف های هرز C۳ و C۴ و سطوح مختلف نیتروژن بر رشد و ماده خشک آفتابگردان

In order to consider the effects of nitrogen and weeds interference (pigweed and lambsquarter) on the sunflower growth and biomass production, an experiment was conducted in a greenhouse in Fasa Township in ۲۰۱۰. The experimental design was completely randomized block with factorial treatment arrangements, replicated three times. The first factor, was the ۳ levels of nitrogen (۰, ۴۶ and ۹۲ kg/ha) and the second factor was the competition of sunflower and weeds in ۵ levels including a pure sunflower only without weeds and ۲ levels of corn and weeds intercropping (pigweed and lamsquarter) and ۲ levels of pure weeds. The results showed that nitrogen application increased shoot biomass of sunflower,   but by increasing weeds density, shoot biomass of sunflower decreased. Increase of nitrogen in different levels of sunflower and lambsquarter, benefited the sunflower, because it increased shoot biomass, but in various pigweed densities, ۴۶kg nitrogen application treatment of the accumulation increased the  sunflower shoot weight. But applying ۹۲ kg nitrogen decreased sunflower shoot biomass. In fact, it expresses that C۴ plants react to Nitrogen more positively. Increasing  nitrogen caused increase of sun flower root in all nitrogen levels.C۴ weeds were more competitive with the increase of nitrogen level, but in lower levels of nitrogen C۳ plants were more successful. Lambsquarter was more competitive for soil sources, especially in the higher nitrogen levels. With the increase of weed accumulations, the ratio of root to shoot increased. Sunflower chlorophyll index in pure and mixed culture with lambsquarter was not significantly affected. But Chlorophyll indices of sun flower and pigweed decreased. Chlorophyll index was independent of weed density but the level of chlorophyll was affected by culture types.The PRY index decreases with the increase of weed density. In the mix of sun flower and lambsquarter the PRY in lambsquarter was lower than that of sun flower and in the mix of sun flower and pigweed the amount of PRY was higher for pigweed. یش{
داد. افزایش نیتروژن باعث افزایش وزن خشک ریشه آفتابگردان در کلیه سطوح گردید. با افزایش نیتروژن توانایی رقابتی علف هرز C۴ افزایش یافت، اما در مقادیر کم نیتروژن گیاهان C۳ موفق تر بودند. شاخص کلروفیل آفتابگردان در کشت خالص و مخلوط با سلمه تره تفاوت معنی داری نداشت. اما در کشت آفتابگردان و تاج خروس شاخص کلروفیل کاهش یافت. میزان وزن خشک نسبی آفتابگردان در مخلوط با علف­های هرز  کاهش یافت. در مخلوط آفتابگردان و سلمه تره میزان وزن خشک نسبی سلمه تره کمتر از آفتابگردان و در مخلوط آفتابگردان و تاج خروس وزن خشک نسبی تاج خروس بیشتر از وزن خشک نسبی آفتابگردان بود. در کل گیاه C۴ تاج خروس استفاده بهتری از نیتروژن کرده و افزودن نیتروژن در مخلوط این گیاه با آفتابگردان باعث افت عملکرد آفتابگردان می شود. در حالیکه در بین دو گیاه C۳آفتابگردان و سلمه، آفتابگردان قابلیت استفاده بهتری از نیتروژن داشته و توانایی رقابتی خود را افزایش می دهد.