Allelopatic effect of five weed species on seed germination of sorghum crops.
Aim of this study was to evaluate the allelopathic effect of five invasive weeds (Sorghum halepense L. Pers., Sonchus arvensis L., Cirsium arvense L. Scop., Xanthium strumarium L.and Aristolochia clematitis L.) in forage crops on two Sorghum crops (Sorghum sudanense (Piper) Stapf and Sorghum vulgare var. technicum (Körn.)). An ex-situ experiment was carried out as follows: 10 seeds of each test variety were placed in Petri dishes between filter paper and the dried weed biomass extract was added at concentrations of 0.1, 0.2, 0.4, 0.8, 1.6 and 3.2% w/v. Petri dishes were placed in a thermostat-operated device at a temperature of 22 ± 2 °C for a seven-days period. Distilled water was used as a control. Number of germinated seeds, % of seed germination against the control, and weed inhibition rate (IR) were measured. Our study revealed that the alellopathic effect of the tested five invasive weeds on seed germination of S. sudanense and S. vulgare var. technicum varied according to the plant species (both weed and cultural) and the concentration applied. Most pronounced negative effect on the germination process of S. sudanense seeds have expressed the cold aqueous extracts from Sonchus arvensis L. and Cirsium arvense (L.) Scop. - IR varied from 4.67-5.0% up to 70.3% at the highest test concentrations (p<0.05). Maximal inhibition of seed germination of S. vulgare var. technicum in comparison with the control was found at 3.2% w/v extract of Sorghum halepense (L.) Pers. (IR=58.4%), followed by the two highest concentrations of Xanthium strumarium L. extract (IR=41.6-45.9%).