Allelopathic effects of Chenopodium album, Amaranthus retroflexus and Cynodon dactylon on germination and growth of safflower

According to the importance and diversity of Chenopodium album, Cynodon dactylon and Amaranthus retroflexus in safflower fields and significant role of safflower (Carthamus tinctorius L.) as an oil seed, an experiment was conducted using CRD based factorial design with three replications to study the allelopathic effects of root and shoot extracts of these weeds on germination and early growth stages of safflower in 2006. Analysis of variance at germination stage showed that main and interaction effects on germination %, seedling length, dry weight, coefficient of germination rate and germination time were significant. Root and shoot extracts of Amaranthus retroflexus, shoot extract of Chenopodium album and root extract of Cynodon dactylon inhibited germination entirely. The extract of the rest of weed decreased at least 52.5% seedling dry weight and near 80% germination percentage. In greenhouse experiment the effect of weed type on height, root and shoot dry weight, leaf area and biomass was significant. Different parts of weeds showed highly significant effect on all attributes. Interaction effects of weed type x weed part had significant impact on root dry weight, leaf area and biomass. Chenopodium album had the most impact on decreasing root and shoot dry weight, root length and biomass. Amaranthus retroflexus also caused high reduction of safflower height and leaf area. Weed extracts significantly decreased plant height at least 19.07% and root dry weight as highest 92.5% in compare with control. This research clearly showed that the weeds disturbed the safflower germination and growth by producing allelopathic compounds and caused reduction in crop establishment.