Studies on Effects of Russian Knapweed (Acroptilon repens (L.) DC) and Butter Cup (Ranunculus damascenus Boiss and Gaill), Causing Problem in Winter Wheat, on Yield and Determination of Their Economical Thresholds in Van

摘要

In this study, effects of different densities of Russian knapweed (Acroptilon repens (L.) DC) and butter cup (Ranunculus damascenus Boiss and Gaill) on yield and yield components of winter wheat were researched in Van. It was determinated that, increasing densities of A. repens have decreased number of spike, grain, straw and total yield of wheat. But, increasing densities of R. damascenus have not been effective on yield and yield components because of being small constitution and having short growing period. Ten plants per m2 of A. repens reduced grain and straw yields respectively 24.3 and 19%. These amounts are over economical threshold, therefore weed cotrol must be done. When the densities were 60 plants/m2, loss of grain yield was about 50% and loss of straw yield was about 40%.