Primary growth of root and shoot of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) in competition for nitrogen

In order to study on primary growth of shoot and root in wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) and assessment of their competition ability in different levels of nitrogen during vegetative stage of growth, a factorial greenhouse experiment conducted based on completely randomized block design with three replications in research glasshouse of faculty of agriculture, at Ferdowsi University of Mashhad in 2008. The first factor consisted of five different levels of nitrogen (1, 4, 8, 12 and 16 mM), the second factor was five different densities (0, 2, 4, 6 and 8 plants per pot) of wild oat and the third factor was competition condition (no-competition and competition with wheat (density of 8 plants per pot)). The experiment was finished at the end of vegetative growth stage of wheat. Results demonstrated that the effects of competition, wild oat density, nitrogen level and their binary interactions on shoot dry weight (SDW) of wild oat were significant. Increasing of nitrogen increased the SDW of wild oat in both competition and no-competition conditions. The competition of wheat could also decrease this characteristic in all nitrogen levels. The interactions of experimental factors also have significant effect on SWD of wheat as well as root dry weigh (RDW) of wild oat. Nitrogen has no significant effect on SWD of wheat in high levels of weed densities. Completion between wild oat and wheat decreased shoot/root dry weight just in wild oat and had no significant in wheat. Result totally showed that increase of nitrogen at low and high densities of wild oat, increased the dominance of wheat and wild oat, respectively.