Effect of Four Cover Crop Species on Weed Control and Population Changes in Karaj Region

This experiment was conducted during 2015-2016 in Karaj, Iran to investigate the effect of cover crops on weed control and the use of herbicide on establishment of cover crops as a split-plot arrangement in a randomized complete block design with three replications. Main factors were Festuca ovina, Festuca rubra, Agropyron desertorum, Bromus tomentellus and control (no cover crops, weedy) and sub factor was Bromoxynil + MCPA (Bromicide M. A EC. 40) herbicide in four levels: 0, 300, 450 and 600 gha-1. Based on the findings, B. tomentellus and F. ovina species had the highest cover crop dry mater (8 and 5 kg/ m2 respectively). B. tomentellus and F. ovina species had the highest reduction in weed densities (86% and 67%, respectively) and dry weights (81% and 71%respectively) compared to the control. The interaction between cover crops and herbicide on total dry weight of weeds was significant. The most common weeds of the experiment were Alyssum desertorum, Descurainia Sophia and Polygonum aviculare. The mean dry weight reduction of dominant weeds by cover crops compared to control for D. sophia, A. desertorum and P. aviculare were 83%, 71% and 89%, respectively. The highest dry weight loss of dominant weeds was belonged to B. tomentellus and F. ovina treatments. Based on the Shannon Wiener index, the highest reductions of diversity compared to the control (1. 5) were observed for B. tomentellus (0. 6) and F. ovina (0. 73).