Investigation on allelopathic effects of plant oils and extractson weed seed germination

In this study, the bioherbicidal effects of Chinaberry tree (Melia azedarach L.) fruit extract, lemon peel extract and Clove (Syzygium aromaticum L.), Thyme (Origanum syriacum L.), Peppermint (Mentha spicata subsp. spicata L.), Eucalyptus (Eucalyptus globulus Labill.) and Lavender (Lavandula angustifolia Mill.) essential oils on the germination of important weed species Redroot pigweed (Amaranthus retroflexus L.) and Italian ryegrass (Lolium multiflorum L.) seeds were investigated. Chinaberry tree fruits and lemon peel extracts were boiled and the obtained extract was tested on weed seeds separately in 3 fractions. In addition, Chinaberry tree oil was obtained in 2 fractions with the technology of the soxhlet device by grinding the fruits.Defne Company oils were used in essential oils. The oils and their extracts were tested in petri dishes at 7 different doses (0% control, 1%, 5%, 10%, 25%, 50% and 100% µl/petri) in climatic chambers operating at 25±2°C and the trials continued for 28 days. As a result, Redroot pigweed , exhibited complete bioherbicidal efficacy with each dose of essential oils, while the 1% dosages of essential oils inhibited the germination of Italian ryegrass seeds by 71% in clove oil, 100% in thyme oil, 68% in lavender oil, 97% in peppermint oil, and 63% in eucalyptus oil.The inhibitory effects of the obtained extracts on seed germination differed in the two weed species. It was determined that the inhibitory effect of the Chinaberry tree fruit extract on the germination of Redroot pigweed seeds was at the highest 100%, 50% and 25% doses, and the effect rate decreased after the 10% dose. It was observed that the most important dose preventing germination in Italian ryegrass seeds was 100%. On the other hand, lemon peel extract, , prevented the germination of Redroot pigweed seeds at 100% and 50% doses of the highest upper and lower fraction applications, while it was observed that it was not very effective on Italian ryegrass seeds.