Assessment of intra- and inter-specific competition between wheat (Triticum aestivum L.) and hoary cress (Cardaria draba L.) under different levels of nitrogen by reciprocal yield model

The ability of Hoary cress to absorb water and nutrients, due to creeping and extensive root system, indicates that this weed is importunate competitor for crop plants. To determine intra- and inter-specific competition between wheat and hoary cress by reciprocal yield model and other competition indices under different nitrogen levels, a factorial experiment based on RCBD was conducted with three replications in Research Greenhouse of Faculty of Agriculture, University of Birjand during 2013. Factors considered included pure nitrogen in three levels (0.05, 0.1 and 0.2 gr/kg soil), wheat density in four levels (0, 4, 8 and 12 plants per pot) and Hoary cress density in four levels (0, 2, 4 and6 plants per pot). The result of reciprocal yield model showed that in wheat intera- specific competition was higher than inter-specific competition, but in Hoary cress, intera- specific was higher. Relative competitiveness assessment showed that the effect of a wheat plant at three levels, 0.05, 0.1 and 0.2 grN/kg soil Was equal to 5.1, 4.45 and 4.42 Hoary cress plant respectively, and the effect of a wheat plant at the same fertilizer, Was equivalent whit 94, 84 and 88% of the wheat plant respectively.