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    Determination of Crop Water Stress Index and Irrigation Timing on Olive Trees Using a Handheld Infrared Thermometer
    (Asce-Amer Soc Civil Engineers, 2013) Akkuzu, Erhan; Kaya, Unal; Camoglu, Gokhan; Mengu, Gulay Pamuk; Asik, Serafettin
    Leaf temperature has long been recognized as an indicator of water availability. The stress level in a plant can be quantified from leaf temperature by using the crop water stress index (CWSI). In this study, it was investigated whether infrared thermometer measurements and accordingly CWSI could be used to create irrigation schedules for olive trees (cultivated variety Memecik). The research was conducted at the olive tree plantation of the Olive Research Station between 2009 and 2010. In the study, the effects of different irrigation treatments on the yield, canopy temperature, and CWSI of olive trees were investigated, and the optimum irrigation schedule was determined according to the findings. Seven different water application treatments were created using the drip irrigation method. Five treatments consisted of irrigating at a rate equivalent to 25% (S-0.25), 50% (S-0.50), 75% (S-0.75), 100% (S-1.00), and 125% (S-1.25) of the cumulative evaporation in 5days from a Class A evaporation pan. The other two treatments consisted of a treatment in which the humidity lost at a soil depth of 0-90cm was replenished each time to the field capacity (Control, S-C) and a treatment in which no irrigation was performed and cultivation was carried out under completely rain-based conditions (Stress, S-0). In the study, the amounts of irrigation water applied to the treatments ranged from 0 to 809mm, and the crop water consumption values varied from 127 to 853mm according to the average of both years. The highest water-use efficiency was obtained in the S-0 treatment, whereas the highest irrigation water-use efficiency was obtained from the S-0.50 treatment. One of the important findings of this study was that handheld infrared thermometer can be used for stress detection and irrigation scheduling of olive trees. When the mean CWSI values in the experimental years were examined in terms of the irrigation treatments, the CWSI values ranged from 0 to 0.68 in 2009 and from 0.02 to 0.71 in 2010. In both years, the highest values were recorded in the S-0 treatment, and the lowest values in the S-1.25 treatment. When water-use efficiency is evaluated along with CWSI values, irrigation can be recommended at half of the evaporation from a Class A evaporation pan (S-0.50, when CWSI values reach 0.39). In conditions in which water sources are insufficient, it can be recommended that irrigation be started when evaporation is a quarter (S-0.25), that is, when CWSI values reach 0.49.
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    Diurnal Variation of Canopy Temperature Differences and Leaf Water Potential of Field-Grown Olive (Olea europaea L. cv. Memecik) Trees
    (Univ Philippines Los Banos, 2010) Akkuzu, Erhan; Camoglu, Gokhan; Kaya, Unal
    This study reports the variations of leaf water potential (LWP) and canopy temperature (T-c) of irrigated and droughted field-grown olive (Olea europaea L. cv. Memecik) trees. The trees were subjected to two irrigation treatments: irrigated at 100% of crop evapotranspiration (control), and a non-irrigated (stressed) treatment. The diurnal behavior of LWP and T-c in response to water stress and the evaporative demand of the atmosphere was studied for 4 consecutive days in August 2009. In the control, canopy temperature was found to be lower than the air temperature (T-a), but in the stress treatment, canopy temperature was higher than air temperature. The maximum difference between the canopy temperatures of the two treatments was 2.7 degrees C. In the control treatment, midday LWP values were about -2.5 MPa, while in the stress treatment, they fell below -4MPa. The greatest difference between treatments in both canopy temperatures and LWP occurred around midday. A negative linear relationship was found between (T-c-T-a) and LWP, and between vapor pressure deficit (VPD) and LWP. VPD values ranged from 0.6-3.9 kPa. No significant linear relationship was found between T-c-T-a and VPD. Increase in water deficit resulted in an increase in canopy temperature, which eventually exceeded ambient air temperature and may have negatively affected leaf function and crop productivity. Temperature gradients also influenced the water potential of olive trees.
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    Effect of Different Irrigation Levels on the Yield and Traits of Memecik Olive Trees (Olea europaea L.) in the Aegean Coastal Region of Turkey
    (Asce-Amer Soc Civil Engineers, 2014) Asik, Serafettin; Kaya, Unal; Camoglu, Gokhan; Akkuzu, Erhan; Olmez, Handan Ataol; Avci, Musa
    Although olive trees are well known to be resistant to drought, the economic advantages of irrigation have been clearly demonstrated. Today, the olive growing areas in the Mediterranean Basin suffer from water shortages and increased competition from other sectors for the available water resources. This study was conducted in an olive tree plantation in western Turkey in 2008-2010. In the study, the effects of different irrigation levels on yield and the physiological and morphological development of olive trees (Olea europaea L. cv. Memecik) were investigated, and the optimal irrigation schedule was determined according to the findings of the study. Six different irrigation treatments were created using a drip irrigation system. The treatments were: a control (SC) in which irrigation amounts were scheduled based on the soil moisture content of the top 90cm of root depth by the gravimetric method and five treatments that received an amount of water equivalent to 25% (S0.25), 50% (S0.50), 75% (S0.75), 100% (S1.00), and 125% (S1.25) of the five-day cumulative evaporation from a class A Pan. The total amount of irrigation water applied to the treatments during the irrigation seasons ranged from 175 to 874mm; however, actual evapotranspiration ranged from 253 to 902mm. In both cases, the lowest and highest values were, respectively, in S0.25 and S1.25. Compared with the amount of irrigation water applied to SC, approximately 72% less water was applied to S0.25 and 40% more water was applied to S1.25. Yields between treatments ranged from 24.88 to 37.35kgtree-1 and from 0.47 to 0.63kgm-3, but no significant differences were detected in yield between treatments (p<0.05). Significant differences between treatments were detected in some morphological features such as shoot length, shoot diameter, canopy volume, and fruit set ratio. In contrast, no significant differences between treatments were detected in other morphological features such as number of buds on a shoot, number of flowers per bud, and number of flowers per shoot. Taking the average of the years of the experiment, the lowest and highest values for predawn, midmorning and midday measurements of leaf water potential were obtained, respectively, from S0.25 and S1.25. It was concluded from the findings of this study that irrigation of Memecik olive trees should be scheduled based on the amount of water equivalent to 25% (S0.25) of the five-day cumulative evaporation from a class A pan. Irrigation scheduling using deficit irrigation allowed considerable water savings in olives, with minimal effects on yield. (C) 2014 American Society of Civil Engineers.
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    Examination of Temporal Variation in the Physiological Parameters of Olive Trees in Various Deficit Irrigation Strategies
    (Asce-Amer Soc Civil Engineers, 2024) Mengu, Guelay Pamuk; Pouyafard, Nima; Kaya, Unal; Akkuzu, Erhan
    Sensitive irrigation programming requires both a good knowledge of plant physiology regarding water use and the monitoring of the effect of water stress on plant physiology. In this study, the effect of different irrigation strategies on full-grown olive trees of the Memecik variety irrigated by the drip irrigation method was investigated over three crop seasons (2012-2013, 2013-2014, and 2014-2015), and the possibility of using these strategies in forming an irrigation program was examined. The experiment consisted of five irrigation treatments with three replications in a random block design. One significant finding after the three years of observation in the study was that it was possible to determine in a simple and sensitive way the temporal responses of olive trees under conditions of water stress with predawn plant water potential, stomatal conductance, and plant water stress index but not chlorophyll content (SPAD value). Statistically significant differences were found between the treatments in the measurements made. Taking into account the three-year averages of treatment values for water applications, acceptable threshold values for predawn plant water potential, stomatal conductance, and plant water stress index are -1.64 MPa, 330 mmol m-2 s-1, and 0.37, respectively. It is easy to put these measurements into practice, and doing so will enable very significant water savings in Mediterranean climate conditions.
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    PREDICTION OF LEAF WATER STATUS USING SPECTRAL INDICES FOR YOUNG OLIVE TREES
    (Parlar Scientific Publications (P S P), 2013) Camoglu, Gokhan; Kaya, Unal; Akkuzu, Erhan; Genc, Levent; Gurbuz, Melek; Mengu, Gulay Pamuk; Kizil, Unal
    It is important to determine the plant water stress before it can reduce the yield or becomes visible. The aim of this study was to investigate the relationship between remotely sensed hyperspectral reflectance indices and leaf water status (LWS) of olive seedlings (Olea europaea L. cv. 'Ayvalik', 'D9', 'D36', 'Erdek Yaglik', 'Frantoio' and 'Gemlik') at different irrigation regime. A pot experiment was conducted in field conditions with 2-years old olive seedlings for the seasons 2011 and 2012. Four levels of water treatment were applied to the pots to bring about different stress conditions; no stress (I-100), mild stress (I-66), severe stress (I-33) and full stress (I-0). Leaf water potential (LWP) and relative water content (RWC) were determined to assess the LWS of the plants. In addition, canopy spectral reflectance was measured with a handheld spectroradiometer and several spectral vegetation indices were calculated using canopy reflectance data. Analysis showed that the irrigation requirement of Frantoio cultivar was the highest when compared to that of other cultivars, while the lowest amount of water was required by Ayvalik cultivar. According to the stepwise multiple linear regression (SMLR) analysis between spectral indices and LWS of olive seedlings, the coefficient of determination (R-2) of model between RWC and Photochemical Reflectance Index (PRI) was 0.70, while it was 0.81 between LWP and PRI, Soil Adjusted Vegetation Index (SAVI), Normalized Difference Vegetation Index (NDVI) and Normalized Pigment Chlorophyll Index (NPCI). Accordingly, it appeared that LWP could be detected more accurately than RWC using spectral indices. Results of this study indicated that the olive plant was very susceptible to water stress and the remotely sensed spectral data could be used to determine RWC and LWP as an indicator of water stress.
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    PREDICTION OF LEAF WATER STATUS USING SPECTRAL INDICES FOR YOUNG OLIVE TREES
    (Parlar Scientific Publications (P S P), 2013) Camoglu, Gokhan; Kaya, Unal; Akkuzu, Erhan; Genc, Levent; Gurbuz, Melek; Mengu, Gulay Pamuk; Kizil, Unal
    It is important to determine the plant water stress before it can reduce the yield or becomes visible. The aim of this study was to investigate the relationship between remotely sensed hyperspectral reflectance indices and leaf water status (LWS) of olive seedlings (Olea europaea L. cv. 'Ayvalik', 'D9', 'D36', 'Erdek Yaglik', 'Frantoio' and 'Gemlik') at different irrigation regime. A pot experiment was conducted in field conditions with 2-years old olive seedlings for the seasons 2011 and 2012. Four levels of water treatment were applied to the pots to bring about different stress conditions; no stress (I-100), mild stress (I-66), severe stress (I-33) and full stress (I-0). Leaf water potential (LWP) and relative water content (RWC) were determined to assess the LWS of the plants. In addition, canopy spectral reflectance was measured with a handheld spectroradiometer and several spectral vegetation indices were calculated using canopy reflectance data. Analysis showed that the irrigation requirement of Frantoio cultivar was the highest when compared to that of other cultivars, while the lowest amount of water was required by Ayvalik cultivar. According to the stepwise multiple linear regression (SMLR) analysis between spectral indices and LWS of olive seedlings, the coefficient of determination (R-2) of model between RWC and Photochemical Reflectance Index (PRI) was 0.70, while it was 0.81 between LWP and PRI, Soil Adjusted Vegetation Index (SAVI), Normalized Difference Vegetation Index (NDVI) and Normalized Pigment Chlorophyll Index (NPCI). Accordingly, it appeared that LWP could be detected more accurately than RWC using spectral indices. Results of this study indicated that the olive plant was very susceptible to water stress and the remotely sensed spectral data could be used to determine RWC and LWP as an indicator of water stress.
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    Three (Turkish) olive cultivars display contrasting salt stress-coping mechanisms under high salinity
    (Springer Heidelberg, 2021) Ayaz, Meltem; Varol, Nurhan; Yolcu, Seher; Pelvan, Alpay; Kaya, Unal; Aydogdu, Erol; Bor, Melike
    Key message All olive cultivars survived high salinity, yet, the question was how they orchestrated antioxidative defense, mannitol accumulation and ion sequestration with different efficiencies due to their genetic makeup. A Mediterranean plant, Olea europaea (olive) is well adapted to high temperature, high light intensity and dry soil conditions hence accepted to be moderately salt tolerant. Control of Na+ and Cl- uptake, accumulation of osmoprotectants and high antioxidative capacity were all attributed to salt stress tolerance of olive, however, there is a great discrepancy between the efficiency and onset of these processes among different cultivars. In present study, three olive cultivars namely Ayvalik, Gemlik and Kilis which are well adapted to different climatic regions extending from cool and high precipitation receiving regions to long hot and dry periods with high light intensity through the growth season were tested for their relative salt-tolerance mechanisms. For this aim, 1-year-old cuttings of these cultivars were treated with 0, 100, 200 and 300 mM NaCl for 30 days. Several physiological and biochemical processes along with their growth performance were analyzed during the experimental period. In general, we found discrepancies in salt stress-coping strategies of these cultivars. Efficient osmoprotection in Gemlik cv. lead to a better leaf water status and photosynthetic performance while, active ion sequestration and high levels of SOD and POX enabled Kilis cv. to be protected from the negative impact of salinity. Moreover, Ayvalik cv. accumulated high levels of mannitol that probably served as an antioxidative molecule to cope with salt stress.