Study on the allelopathic effect of Amaranthus retroflexus L., Datura stramonium L. and Panicum miliaceum L. on the germination of maize
Plant extracts of Amaranthus retroflexus showed an inhibitory effect on the development of both cotyledons and rootlets of maize in petri dish trials. In pot experiments, among the three examined weeds, dry plant residues of Amaranthus hindered the germination of maize to the greatest extent. It showed also a negative effect on the shoot length and weight, while there was a positive effect on the root length and weight. A 2.5% concentration of Datura stramonium plant extracts showed a stimulative effect, but the 5% and 7.5% extracts inhibited the shoot and root development of germinating maize. In spite of a 60% germination rate, the incorporation of dry plant residues into the soil did not show any significant effect on the development of shoots, but a stimulative effect on root development was observed. However, the dry weight of roots exceeded the control values only at a concentration of 7.5%. Plant extract of Panicum miliaceum had a stimulative effect on the shoot and root development of maize. Dry plant parts in the soil of the pots hindered the germination of maize, but significant effects on the shoot and root lengths could not be proven. At the 7.5% ratio the dry weight of shoots was higher than the control values, but all the other soil-plant part ratios caused lower values.