Allelopathic effects of medicinal plant madder (Rubia tinctorum) on germination characteristics and seedling growth of sorghum (Sorghum bicolor), corn (Zea mays), field bindweed (Convolvolus arvense) and Johnsongrass (Sorghum halepense)

Excessive use of chemical herbicides has resulted to many problems such as adverse environmental impacts, contamination of groundwater and resistant weeds. Therefore, researchers are looking for solutions to reduce the use of herbicides as more as possible. One effective approach is to use the characteristics of allelopathic plants. To evaluate the allelopathic effects of extracts of madder on seed germination of several crops (corn and sorghum) and weeds (Johnsongrass and field bindweed), four separate laboratory experiments were conducted in 2011 at Yazd University of Applied Science. The experimental design was a completely randomized with 4 replications and 5 treatments. Treatments were madder extract at 5 levels (zero, 25%, 50%, 75% and 100%, respectively). The results showed that the extract of madder could decrease traits such as germination percentage and germination rate, root and shoot length, root to shoot ratio (R / S), seedling vigor index and total dry weight of all plants significantly (p