46 Behdarvand et al. Int. J. Biosci. 2014 RESEARCH PAPER OPEN ACCESS Interference effects of wild mustard and wild oat on nitrogen use efficiency, nitrogen and chlorophyll content of wheat in response to nitrogen application Pejman Behdarvand 1* , Ganesh S. Chinchanikar 2 , Morteza Siavoshi 3 1 Department of Agricultural and Natural Resources, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran 2 Department of Botany, University of Pune, India 3 Department of Agricultural Science, Payame Noor University, Iran Key words: Interference, nitrogen, wheat, wild mustard, wild oat. http://dx.doi.org/10.12692/ijb/4.3.46-52 Article published on February 05, 2014 Abstract Field experiment was conducted to evaluate nitrogen use efficiency, nitrogen and chlorophyll content of wheat in response to changes in weed density and nitrogen application. The statistical analysis of data indicated that the content of nitrogen and chlorophyll of wheat flag leaf significantly increased by increasing nitrogen level, however the nitrogen use efficiency decreased. The nitrogen use efficiency at 210 kg N ha -1 was 22.74 kg/kg lower than 90 kg N ha -1 . Interspecific competition of wild mustard and wild oat significantly decreased the nitrogen use efficiency, nitrogen and chlorophyll content. The density of 15 plants of wild mustard and 75 plants of wild oat decreased the NUE of wheat by 28.2 and 27.3 % as compared to their zero density respectively. * Corresponding Author: Pejman Behdarvand  pbehdarvand@yahoo.com International Journal of Biosciences | IJB | ISSN: 2220-6655 (Print) 2222-5234 (Online) http://www.innspub.net Vol. 4, No. 3, p. 46-52, 2014