) Triticum aestivum L( در گندم پاييزه )Sinapis arvensis L( آستانه خسارت اقتصادي رقابت خردل وحشي

Economic threshold of wild mustard (Sinapis arvensis L.)competition in winter wheat (Triticum aestivum L.)

In order to determine economic threshold of wild mustard competition in winter wheat, and to evaluate economic threshold response to wheat seed rate and nitrogen fertilizer, an additive series experiment was conducted during 2001-2002 at agricultural research station of mashhad university. The experiment included 3 factors: wheat seed rate (175, 215, and 255 kg/ha), nitrogen rate (150, and 225 kg N/ha), and wide range of wild mustard densities. Rectangular hyperbola equation was used to describe wheat yield losses. With increasing wheat seed rate from low to medium, and high level, the maximum yield loss due to high density of wild mustard, was reduced from 57.17 to 50.88, and 41.66, respectively. Increasing nitrogen rate over optimum rate of wheat, resulted in increased of percentage yield loss per unit wild mustard density as density approach zero and also maximum yield loss due to high density of wild mustard. Results showed that economic threshold was increased 116 % due to increase of wheat seed rate, and decreased 53 % follow by increasing of nitrogen over optimum rate of wheat.