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    Determination of water stress with spectral reflectance on sweet corn (Zea mays L.) using classification tree (CT) analysis
    (Lithuanian Research Centre Agriculture & Forestry, 2013) Genç, Levent; Nalpulat, Melis; Kızıl, Ünal; Mirik, Mustafa; Smith, Scot E.; Mendes, Mehmet
    Water stress is one of the most important growth limiting factors in crop production. Several methods have been used to detect and evaluate the effect of water stress on plants. The use of remote sensing is deemed particularly and practically suitable for assessing water stress and implementing appropriate management strategies because it presents unique advantages of repeatability, accuracy, and cost-effectiveness over the ground-based surveys for water stress detection. The objectives of this study were to 1) determine the effect of water stress on sweet corn (Zea mays L.) using spectral indices and chlorophyll readings and 2) evaluate the reflectance spectra using the classification tree (CT) method for distinguishing water stress levels/severity. Spectral measurements and chlorophyll readings were taken on sweet corn exposed to four levels of water stress with 0,33,66 and 100 % of pot capacity (PC) before and after each watering time. The results demonstrated that reflectance in the red portion (600-700 mu) of the electromagnetic spectrum decreased and increased in the near infrared (NIR) region (700-900 nm) with the increasing field capacity of water level. Reflectance measured before the irrigation was generally higher than after irrigation in the NW region and lower in the red region. However, when the four levels of PC and before or after irrigation only were compared, reflectance spectra indicated that water stressed corn plants absorbed less light in the visible and more light in the NIR regions of the spectrum than the less water stressed and unstressed plants. There was a similar trend to reflectance behaviour of water stress levels using chlorophyll readings that decreased over time. The CT analysis revealed that water stress can be assessed and differentiated using chlorophyll readings and reflectance data when transformed into spectral vegetation indices.
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    Identification of phosphorus-sensitive regions using field data, remote sensing imagery and kriging techniques to mitigate overuse of fertilizer in a northwestern town of Turkey
    (2011) Genç, Levent; Kizil, Ünal; Miiftiio?lu, Nuray Mücella; Smith, Scot E.
    As part of its environmental compliance program required for joining the European Union, Turkey must deal with the problem of excess runoff of nutrients from both chemical fertilizers and manure into water. Manure and other fertilizers cause eutrophication and other water quality problems. It had been thought that phosphorus, which is in manure as well as chemical fertilizers, was so strongly bound to soil particles that it did not readily leach into water. However, recent studies show that phosphorus is mobile and so poses a threat to water quality. For this study, soil testing for phosphorus was performed in 832 fields within a 133,000 ha area in the Canakkale province of northwest Turkey. The region is dominated by crop fields, and also a large number of livestock. Soils were classified into five categories with respect to phosphorus sensitivity. Satellite imagery was used to calculate the size of each class. Over 70,000 hectares of cropland were classified as phosphorus-sensitive due to overapplication of chemical fertilizers. Chemical fertilizer applications increased not only the phosphorus values, but also the zinc content of the soil. © by PSP.
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    Öğe
    IDENTIFICATION OF PHOSPHORUS-SENSITIVE REGIONS USING FIELD DATA, REMOTE SENSING IMAGERY AND KRIGING TECHNIQUES TO MITIGATE OVERUSE OF FERTILIZER IN A NORTHWESTERN TOWN OF TURKEY
    (Parlar Scientific Publications (P S P), 2011) Genç, Levent; Kızıl, Ünal; Müftüoğlu, Nuray Mücella; Smith, Scot E.
    As part of its environmental compliance program required for joining the European Union, Turkey must deal with the problem of excess runoff of nutrients from both chemical fertilizers and manure into water. Manure and other fertilizers cause eutrophication and other water quality problems. It had been thought that phosphorus, which is in manure as well as chemical fertilizers, was so strongly bound to soil particles that it did not readily leach into water. However, recent studies show that phosphorus is mobile and so poses a threat to water quality. For this study, soil testing for phosphorus was performed in 832 fields within a 133,000 ha area in the Canakkale province of northwest Turkey. The region is dominated by crop fields, and also a large number of livestock. Soils were classified into five categories with respect to phosphorus sensitivity. Satellite imagery was used to calculate the size of each class. Over 70,000 hectares of cropland were classified as phosphorus-sensitive due to overapplication of chemical fertilizers. Chemical fertilizer applications increased not only the phosphorus values, but also the zinc content of the soil.