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    Chemical Composition and Herbicidal Activities of Essential Oil from Aerial Parts of Origanum Hybrids Grown in Different Global Climate Scenarios on Seed Germination of Amaranthus palmeri
    (Taylor & Francis Ltd, 2021) Yasar, Ayse; Karaman, Yucel; Gokbulut, Incilay; Tursun, Ayse Ozlem; Tursun, Nihat; Uremis, Ilhan; Arslan, Mehmet
    The present study aimed to investigate the changes in the essential oil contents of some Origanum hybrids grown at different carbon dioxide (400 and 800 ppm) levels in a fully automated carbon dioxide greenhouse. The chemical composition of essential oils was analyzed gas chromatography/ mass spectrometry (GC/MS). It was found that, among the Origanum hybrids, there were differences between the essential oil contents of those grown under natural conditions and controlled greenhouse conditions. While an increase in carbon dioxide level significantly increased the thymol and carvacrol components, which are among important monoterpene components, of Origanum syriacum x O. onites and O. syriacum x O. vulgare hybrids, whereas it led to a decrease in O. syriacum x O. majorona hybrid. To determine the effects on germination of Amaranthus palmeri S. Watson seeds under laboratory conditions, the essential oils were used at 0.5, 1, 2, and 4 mu l/petri doses. The most effective doses of essential oils for preventing the germination of A. palmeri seed were found to be 2 and 4 mu l/petri. In preventing the germination of seeds, the most effective (100 %) application for all the essential oils was achieved with O. syriacum x O. onites hybrid grown at 800 ppm. These results show that the CO2 increases that may occur as a result of climate change in the next years may lead to changes in the content of essential oils in Origanum hybrids and may have the potential to be used as bio-herbicidal to prevent the germination of A palmeri.
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    Critical Period for Weed control in Sunflower and Effects of Applications on Weed Species and Diversity
    (Kahramanmaras Sutcu Imam Univ Rektorlugu, 2022) Ozkil, Mine; Torun, Hilmi; Eymirli, Serdar; Uremis, Ilhan; Karaman, Yucel; Tursun, Nihat
    This study was carried out under field conditions in Adana, Turkey in 2018 and 2019 to determine the critical period for weed control in sunflower depending on the daily growth temperature (GDD) and weed species. A log-logistic model with four parameters was used to determine the relationship between relative crop yield and both increased weed intervention time and length of weed-free periods. In addition, dominant weeds and weed densities were determined in the experimental area. Data obtained from different periods of weed intervention were compared with data obtained from seasonal weed-free plots. During the sunflower growing season, 37.4% - 41.04% yield loss was determined in sunflower due to weed competition. For 5% acceptable yield loss in the first year, the critical period in weed control was determined as 243-1181 GDD; this is 24-86 days after the crop emergence (DAE). It was found between 269 and 1409 GDD (16-72 DAE) in the second year. In sunflower, it was determined that the removal of weeds from the plot in the weed-free period started within 2-3 weeks from the emergence and continued for 10-12 weeks. These findings may help sunflower growers to plan and implement cost-effective and appropriate weed control programs.