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Öğe Critical Period for Weed control in Sunflower and Effects of Applications on Weed Species and Diversity(2022) ÖZKİL, MİNE; torun, hilmi; EYMİRLİ, SERDAR; Üremiş, İlhan; KARAMAN, YÜCEL; Tursun, NihatThis 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.Öğe Effects of CO2 and temperature levels on glyphosate activity and growth of seven weed species(2025) BOZDOĞAN, OLCAY; Jabran, Khawar; Tursun, Nihat; KARAMAN, YÜCELChanges in environmental conditions have a major impact on weed growth and their susceptibility to applied herbicides. We studied the effects of CO2 and temperature levels on the glyphosate (480 g/l Glyphosate Isopropylamin salt) activity and growth of seven weed species. Three temperature levels (control or normal temperature 26/16 °C (14/10 day/night), normal temperature + 3°C i.e., 29/19 °C and normal temperature + 6 °C i.e., 32/22 °C), and four CO2 levels (control i.e., 400 ppm, 600 ppm, 800 ppm, and 1000 ppm) were tested. Six doses of glyphosate were: i) ¼, ii) ½, iii) full dose (1440 g a.i./ha), iv) 2-times, v) 4-times, and vi) 8-times of the recommended dose, at 4-6 leaf stage. Generally, the increase in CO2 and temperature improved weed growth. For most weed species, the most favourable temperature and CO2 levels were 29 oC and 800 ppm to 1000 ppm. The ED50 (effective dose 50) value for Echinochloa colonum (L.) Link., Amaranthus retroflexus L., Amaranthus palmeri S. Watson, Portulacaa oleracea L., Solanum nigrum L., Sorghum halepense (L.) Pers. and Physalis angulata L. showed that some weeds will likely become tolerant to glyphosate with climate change. With increasing temperature and CO2 concentration, ED value increases, meaning higher herbicide doses are required to control these weeds. As a result, using more herbicides in agricultural areas in the coming years will cause producers to experience more costs and the herbicide resistance problem in weeds will increase to much higher levels.Öğe Molecular Characterization and Dose-Response to 2,4-D Herbicide in Convolvulus arvensis Populations in Türkiye(2024) KARAMAN, YÜCEL; Tursun, Nihat; Sipahioglu, Hikmet MuratField bindweed (Convolvulus arvensis L.) is an important weed species in agricultural areas in Türkiye and worldwide. The study, conducted in 2018-2019, involved collecting seeds from 16 different provinces in Türkiye (Adana, Ankara, Çanakkale, Denizli, Diyarbakır, Erzurum, Hatay, İzmir, Karaman, Kayseri, Konya, Malatya, Samsun, Şanlıurfa, Tekirdağ and Uşak). These seeds were then germinated under greenhouse conditions (29/19°C day/night), and molecular characterization of the samples was performed. As a result of comparing the samples with a specific reference from NCBI GenBank, it was found that the similarity ratios were close to each other but formed different groups. The study revealed that samples from Adana, Konya and Samsun belonged to different groups in terms of similarity. Subsequently, the dose-response rates of these samples to 2,4-D, a herbicide licensed against field bindweed, were determined. In the dose-response analysis of the herbicides, ED50 values of 131.93, 115.42 and 141.89 g.a.i/ha were determined for Adana, Konya and Samsun, respectively. The study concluded that the dose-response of field bindweed in Adana, Konya and Samsun provinces, belonging to different molecular groups, to 2,4-D herbicide is close to each other but exhibits different values.Öğe The effect of cover crops on composition and diversity of weeds in an apricot orchard(2021) KARAMAN, YÜCEL; IŞIK, Doğan; TURSUN, NihatApricot, Turkey's exports is the important role played by fruit, the weeds are the main factors that cause problems in the apricot orchards. This study was carried out in Malatya between 2014-2016 in order to determine the effects of cover crops on the control of weeds that cause problems in these areas and also on species distribution, diversity and dominance. As annual winter cover plants in the study: Vicia villosa Roth (hairy vetch), Vicia pannonica Crantz (Hungarian vetch), V. pannonica + Triticale (V.pannonica 70% + Triticale 30%) mixture and Phacelia tanacetifolia Bentham (lacy phacelia) and Fagopyrum esculentum Moench (buckwheat) was used as a summer cover plant. Weed diversity index (H) and Simpson's dominance index (Sd) values were also calculated in the study. In addition, applications were subjected to canonical discriminant analysis. The highest value of the weed diversity index (H) in the two-year period was obtained from the weed control plots. It has been determined that perennial weeds (Convolvulus arvensis and Sorghum halepense) are the dominant species in cover plants and there are also differences between practices. It has been determined that annual weeds are generally suppressed and their diversity has decreased significantly in the plots except for F. esculentum. The results obtained from the canonical discriminant analysis showed that the highest numbers of weed species in the 1 st and 2 nd years were found in the weedy control plots and that the cover crops suppressed the weeds.Öğe The effects of essential oils from two different Satureja hortensis L. genotypes harvested at different times on weed seed germination(2024) yaşar, ayşe; KARAMAN, YÜCEL; Tursun, NihatThe most important allelopathic effect of essential oils is that they prevent the germination of some plant seeds. In this study, essential oils were obtained from different form periods (beginning of flowering, mid-flowering and end of flowering) of 2 genotypes of S. hortensis plant. Subsequently, different doses of essential oils (0.5, 1, 2, 4, 8 and 16 µl petri-1) were used from weeds such as giant amaranth (Amaranthus palmeri L.), wild oats (Avena fatua L.), purslane (Portulaca oleracea L.), wild mustard (Sinapis arvensis L.) and cress (Lepidium sativum L.), durum wheat (Triticum durum L.) and pepper (Capsicum annuum L.) seeds from cultivated plants were investigated. According to the results of the study, germination was negatively affected due to the increase in the application doses of essential oils, and the highest effect was determined as 2 µl petri-1 in A. palmeri and oleracea seeds, 4 µl petri-1 in A. fatua seeds and 8 µl petri-1 in S. arvensis. For the effects of essential oil doses, the highest LD50 values for the seeds of A. palmeri, P. oleracea, A. fatua and S. arvensis were found to be 0.159, 0.189, 1.043 and 3.087, respectively, while the highest LD90 values were determined to be 0.547, 0.673, 2.895 and 8.398, respectively. As a result of the study, it was seen that essential oils have a significant bioherbicidal effect on weed seeds and it is thought that this method will make a significant contribution to the alternative control of weeds.
