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Evapotranspiration (ET) constitutes a significant parameter for various operational practices, including water resources management, hydrological calculations, design of large water structures, and design and operation of irrigation systems. Several methods have been developed for estimating potential crop evapotranspiration (ETc) values of field crops. FAO-Penman Monteith's approach, depending on reference evapotranspiration (ETo) and plant coefficients (Kc), is the most common one among these methods. There are several limiting factors in front of the experimental identification of Kc coefficients of field crops in different regions of the world. Previous research revealed significant relationships between spectral vegetation indices (SVI) calculated using remote sensing data and Kc values. However, most of these studies were about the relationships between SVI and Kc rather than the generation of Kc curves, indicating the temporal variations in Kc values to be used in ETc estimation with the aid of SVIs. The primary target of the present study was to generate Kc curves for wheat, barley, grain maize, sunflower, sugar beet, and onion using Normalized Difference Vegetation Index (NDVI) values calculated from Landsat 8 satellite images. Field experiments were conducted in a semi-arid region of Türkiye in the 2015 and 2016 growing seasons. NDVI values were obtained from different fields cultivated under farmers’ conditions. NDVI data were used as time series, and the temporal variations in the highest NDVI values of each image (NDVImax) were analyzed. The lengths of each Kc phenological stage (initial, crop development, mid, and late seasons) were determined for each crop. Kc coefficients were adapted from FAO 56 handbook using meteorological parameters. In this way, Kc curves of relevant field crops were generated, and statistical relationships between NDVImax and Kc values of each crop were determined. Resultant Kc curves complied well with the previous literature. The linear relationships between Kc and NDVImax yielded an R2 of 0.98 for sunflowers and an R2 of 0.97 for the other crops.

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Determination of Kc Curves of Wheat, Barley, Sunflower, Maize (Grain), Sugar Beet, and Onion by using Landsat 8–NDVI Time Series and Relationships between KC and NDVI

  • 章节

  • 发表日期：

    2025年

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  • Eyüp Selim Köksal,
  • Emre Tunca,
  • Sakine Cetin Taner

摘要

Evapotranspiration (ET) constitutes a significant parameter for various operational practices, including water resources management, hydrological calculations, design of large water structures, and design and operation of irrigation systems. Several methods have been developed for estimating potential crop evapotranspiration (ETc) values of field crops. FAO-Penman Monteith's approach, depending on reference evapotranspiration (ETo) and plant coefficients (Kc), is the most common one among these methods. There are several limiting factors in front of the experimental identification of Kc coefficients of field crops in different regions of the world. Previous research revealed significant relationships between spectral vegetation indices (SVI) calculated using remote sensing data and Kc values. However, most of these studies were about the relationships between SVI and Kc rather than the generation of Kc curves, indicating the temporal variations in Kc values to be used in ETc estimation with the aid of SVIs. The primary target of the present study was to generate Kc curves for wheat, barley, grain maize, sunflower, sugar beet, and onion using Normalized Difference Vegetation Index (NDVI) values calculated from Landsat 8 satellite images. Field experiments were conducted in a semi-arid region of Türkiye in the 2015 and 2016 growing seasons. NDVI values were obtained from different fields cultivated under farmers’ conditions. NDVI data were used as time series, and the temporal variations in the highest NDVI values of each image (NDVImax) were analyzed. The lengths of each Kc phenological stage (initial, crop development, mid, and late seasons) were determined for each crop. Kc coefficients were adapted from FAO 56 handbook using meteorological parameters. In this way, Kc curves of relevant field crops were generated, and statistical relationships between NDVImax and Kc values of each crop were determined. Resultant Kc curves complied well with the previous literature. The linear relationships between Kc and NDVImax yielded an R2 of 0.98 for sunflowers and an R2 of 0.97 for the other crops.