R. Naderi - Department of Agronomy, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.
H. Ghadiri - Department of Agronomy, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran.

A two year field experiment was carried out to evaluate the competitive effects of wild mustard densities growing with rapeseed (cultivar Talaye) under different nitrogen rates. Treatments were wild mustard densities (۰, ۱۰, ۲۰, ۳۰, and ۴۰ plant m-۲) and nitrogen (N) rates (۰, ۵۰, ۱۰۰, ۱۵۰, and ۲۰۰ kg N ha-۱). The factorial set of treatments was arranged into a randomized complete block design with four replications. Rapeseed yield and the yield components decreased as wild mustard density increased. At ۰ and ۱۰ wild mustard plants m-۲, grain yield increased with increasing N fertilizer up to ۱۵۰ kg ha-۱. At higher wild mustard densities, grain yield decreased above ۱۰۰ kg N ha-۱. These results indicate that increases in nitrogen application only increased the competitiveness of the weed versus the crop.

Nitrogen rate, Weed density, Interference, Wild mustard