a study of root allelopathic effects of cool season crops on seedling emergence and early growth of sorghum (sorghum bicolor), corn (zea mays) and soybean (glycine max)

to study the root allelopathic effects of cool season crops on germination and early growth of three crops (sorghum, corn, and soybean), an experiment was conducted in seed research laboratory and greenhouse of college of agriculture, university of tehran. the experiment consisted of four cool season crops (wheat, barley, rye and pea) and control as the main plots, three spring-crops (corn, soybean and sorghum) as sub-plots and three sowing times (sowing immediately after physiological maturity, 2 and 4 weeks past physiological maturity) as sub-sub plots. the experiment was arranged as a split-split plot in a completely randomized design of three replications. all traits (seedling emergence percent, seedling emergence rate, as well as plant height and biomass weight) were affected by experimental treatments. rye had the highest allelopathy effect on the evaluated crops. soybean had the greatest susceptibility to root allelopathism as compared with corn and sorghum. delay in sowing time decreased the root allelopathic effects in a way that 4 weeks of delay in sowing time exerted a significant influence on growth traits. mean germination percent and mean germination rate of the evaluated crops increased with a 4 weeks delay in sowing time. also, an increased trend of biomass weight was observed with delay in sowing time.