Purple nutsedge (Cyperus rotundus) foliage and tubers were tested for allelopathic potential against the following weeds; jute Chorchorus olitorius (broad leaved weed), and barnyard grass Echinochloa crus-galli (grassy weed) associated with soybean. In the greenhouse, during 2008 and 2009, foliage and tubers of C. rotundus were mixed with soil surface at 20, 40, 60 and 80 g/kg. C. rotundus negatively affected those of jute and barnyard grass particularly at 80 g. Jute was more susceptible to allelopathy by C. rotundus than barnyard grass. Inhibition in weed dry matter was higher with tuber than foliage residues. Tuber residues reduced the dry weight of jute and barnyard grass by 85.96% of the control and by 58.28% with 80 g, respectively. On the other hand, soybean growth and yield showed a high significant increase compared with unweeded pots. A high-performance liquid chromatography analysis showed that C. rotundus foliage contained the following phenolic acids: caffeic, ferulic, coumaric, benzoic, vanelic, chlorogenic and cinnamic.Tubers contained hydroxybenzoic, caffeic, ferulic, vanelic and chlorogenic.

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The effects of water extracts of Chenopodium album leaves and roots on the growth of grass weed (Setaria viridis) and broad leaf weed (Corchorus olitorius) grown with beans (Phaseolus vulgaris) in greenhouse pots were studied in the National Research Centre, Giza, Egypt. In this experiment fresh leaf and root extracts and their corresponding dry leaf and root extracts at different concentrations were used. There were significant inhibitions in the dry weights of S. viridis and C. olitorius by all extracts at the flowering stage of beans and at harvest. The inhibition effect of all C. album extracts on both weeds (dry weight/pot) depended on the extracted plant organ (leaf or root), its fresh or dry form as well as its concentrations. The inhibition caused by the leaf extract was much higher on weed growth than that of root extract. A higher concentration of fresh leaf extract (25%) had the highest significant inhibition effect. The results also indicated that C. olitorius was more sensitive to the extracts than S. viridis. On the other hand, the inhibition effect of the extracts on the growth of both weeds was accompanied by increased bean growth and yield/plant. The analysis of both leaf and root extracts of C. album revealed that the total content of polyphenols and flavonoids in the leaf extract was more than triple that of the root extract. The results suggested that the fresh leaf extract of C. album may be a possible tool for the development of weed control using natural herbicides.

Background: Allelopathy is an alternative safe strategy for chemical herbicides in controlling weeds. So, two successive greenhouse experiments were conducted to determine the phytotoxicity of pea seed powder on two weeds chard-(broad leaf) and canary grass (grass weed)-infested wheat. Pea seed powder was added to the soil surface at successive rates 20, 40, 60, 80, and 100 g/pot. The pots were cultivated on time (at sowing application) or 1 week after the addition of the pea seed powder. Results: The results indicated that the pea seed powder at 100 g/pot controlled more than 70-80% of both weeds in comparison to the corresponding controls. On the other hand, the inhibitory effect of the pea seed powder on weeds was accompanied by increases in the growth as well as photosynthetic pigments content and consequently wheat yield especially at 80 g/pot. Conclusion: This study suggested that the pea seed powder has allelopathic and phytotoxic effects that controlled investigated weeds in wheat. Analysis of the allelopathic pea seed powder at the applied rates revealed the presence of phenolic compounds and flavonoids. Both allelopathic compounds showed high levels with increasing the pea seed powder rate. The mixing of pea seed powder with the soil surface at 80 g/pot 1 week before sowing was the most efficient treatment in controlling weeds under investigation that consequently achieved the highest wheat yield.