Evaluation of feral rye (Secale cereale L.) interference effects on wheat (Triticum aestivum) cultivars and determination of economic and qualitative threshold of weed

Field experiments were conducted to evaluate the competitive ability of some traditional and new wheat (Triticum aestivum) cultivars with feral rye (Secale cereale L.) in Dargaz. Experimental factors were four wheat cultivars (Sayson, Alvand, Chamran and Sepahan) and plant density of feral rye at five levels of 0, 20, 40, 60 and 80 plants m-2. The new cultivar of Sepahan had lowest initial slope of yield loss (parameter I) and maximum yield loss (parameter A) in biological and grain yield traits. Alvand cultivar had maximum grain yield and number of fertile spikes. Low slope of harvest index loss and initial slope of increasing of feral rye seed blending percentage (parameter s) obtained in both Alvand and Sepahan cultivars. Maximum reduction, due to feral rye interference, resulted in Chamran cultivar that also had maximum population growth rate of weed and minimum economic threshold (ET) among cultivars. Generally, Sayson and Chamran, due to lower competitive ability and more weed seed production than the other two cultivars, were not suitable for cultivation in rye contaminated lands. Also, late maturity and coincidence of sensitive reproductive stages with region warm winds, lead to unsuitability of Sayson cultivation. Generally, Alvand cultivar due to better control of weed population, higher qualitative threshold (QT) and grain yield was provided all benefits of short-term and high-term in the fields infested by rye.