@article{fdi:010064897,
  title = {{E}stimation of crop water requirements : extending the one-step approach to dual crop coefficients},
  author = {{L}homme, {J}ean-{P}aul and {B}oudhina, {N}. and {M}asmoudi, {M}. {M}. and {C}hehbouni, {A}bdelghani},
  editor = {},
  language = {{ENG}},
  abstract = {{C}rop water requirements are commonly estimated with the {FAO}-56 methodology based upon a two-step approach: first a reference evapotranspiration ({ET}0) is calculated from weather variables with the {P}enman-{M}onteith equation, then {ET}0 is multiplied by a tabulated crop-specific coefficient ({K}-c) to determine the water requirement ({ET}c) of a given crop under standard conditions. {T}his method has been challenged to the benefit of a one-step approach, where crop evapotranspiration is directly calculated from a {P}enman-{M}onteith equation, its surface resistance replacing the crop coefficient. {W}hereas the transformation of the two-step approach into a one-step approach has been well documented when a single crop coefficient ({K}-c) is used, the case of dual crop coefficients ({K}-cb for the crop and {K}-e for the soil) has not been treated yet. {T}he present paper examines this specific case. {U}sing a full two-layer model as a reference, it is shown that the {FAO}-56 dual crop coefficient approach can be translated into a one-step approach based upon a modified combination equation. {T}his equation has the basic form of the {P}enman-{M}onteith equation but its surface resistance is calculated as the parallel sum of a foliage resistance (replacing {K}-cb) and a soil surface resistance (replacing {K}-e). {W}e also show that the foliage resistance, which depends on leaf stomatal resistance and leaf area, can be inferred from the basal crop coefficient ({K}-cb) in a way similar to the {M}att-{S}huttleworth method.},
  keywords = {},
  booktitle = {},
  journal = {{H}ydrology and {E}arth {S}ystem {S}ciences},
  volume = {19},
  numero = {7},
  pages = {3287--3299},
  ISSN = {1027-5606},
  year = {2015},
  DOI = {10.5194/hess-19-3287-2015},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064897},
}