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Crop coefficient for drip-irrigated cotton in a Mediterranean environment


A 3-year study was conducted in the eastern Mediterranean region of northern Syria to develop crop coefficient, K c, for drip-irrigated short-season cotton (Gossypium hirsutum L.). Two sets of K c curves were determined, the generalized K c published by the UN’s Food and Agriculture Organization (FAO) that was adjusted for local climate, and the locally developed K c as the ratio of measured cotton evapotranspiration to calculated reference evapotranspiration. The adjusted FAO K c curves were the same for the 3 years. However, the locally developed K c curves not only differed among the 3 years, but also from the adjusted FAO K c. During the mid-season stage, the adjusted FAO K c was 24% higher than the locally developed value of 1.05. Variations in locally developed K c values were caused by normal year-to-year variations in irrigation timing and amount, suggesting sensitivity of K c that cautions against the use of locally developed K c based on limited data (i.e., a single season). On the season, the overestimation of crop evapotranspiration by using adjusted FAO K c was substantial and equivalent to 150 mm water or about two additional irrigations per season. Results caution against blind application of published FAO K c curve, suggesting some local or regional calibration for increased accuracy.

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Correspondence to H. J. Farahani.

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Communicated by A. Kassam.

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Farahani, H.J., Oweis, T.Y. & Izzi, G. Crop coefficient for drip-irrigated cotton in a Mediterranean environment. Irrig Sci 26, 375–383 (2008).

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  • Crop Coefficient
  • Crop Evapotranspiration
  • Crop Growth Stage
  • Mass Balance Error
  • Short Season Cotton