Towards one-step estimation of crop water requirements

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

This article provides theoretical analyses that facilitate the use of the Penman-Monteith equation to make a one-step estimate of crop water requirements. Reluctance to using a one-step estimate results from two outstanding issues, both of which are addressed. First, no method has been yet defined to handle the problem that meteorological variables are commonly available only at 2 m above the ground while, when using the Penman-Monteith equation, they are required at some level above the crop. To resolve this, a blending height is defined in the atmospheric boundary layer (ABL) where meteorological conditions are independent of the underlying crop. Expressions are derived to calculate the aerodynamic resistances to, and the vapor pressure deficit at, the blending height from climate variables at 2 m. Consequently, 2 m climate data can be used in the Penman-Monteith equation, either to estimate transpiration from surface resistance or to calculate surface resistance from measured transpiration. Second, no table of effective values currently exists for the surface resistance of different crops equivalent to that for the crop coefficient. This article calls for field studies to address this need. However, recognizing the need for an interim source of crop-specific surface resistances, a methodology is given for translating the crop coefficient into equivalent surface resistance. To make this translation, it is necessary to specify the relationship between the radiative and aerodynamic energy inputs to evapotranspiration when the crop coefficients were calibrated. Finally, a Penman-Monteith-based, one-step estimation equation is derived that makes proper allowance for the different aerodynamic characteristics of crops in all conditions of atmospheric aridity, and that estimates crop evaporation for any crop of specified height from existing crop coefficients using standard 2 m climate data.

Original languageEnglish (US)
Pages (from-to)925-935
Number of pages11
JournalTransactions of the ASABE
Volume49
Issue number4
StatePublished - Jul 2006

Fingerprint

water requirement
Climate
Crops
crop
crop coefficient
Water
Surface resistance
crops
Vapor Pressure
aerodynamics
Penman-Monteith equation
water
climate
transpiration
Aerodynamics
Transpiration
Meteorological problems
dry environmental conditions
vapor pressure
evapotranspiration

Keywords

  • Crop evaporation
  • Crop water requirements
  • Crop water use
  • Energy balance
  • Evaporation
  • Evapotranspiration
  • Irrigation
  • Irrigation requirements
  • Penman-Monteith
  • Reference crop evaporation

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Biomedical Engineering
  • Food Science
  • Forestry
  • Soil Science

Cite this

Towards one-step estimation of crop water requirements. / Shuttleworth, W. James.

In: Transactions of the ASABE, Vol. 49, No. 4, 07.2006, p. 925-935.

Research output: Contribution to journalArticle

@article{f434a9e2b8fd43b19e3d76a12baf6378,
title = "Towards one-step estimation of crop water requirements",
abstract = "This article provides theoretical analyses that facilitate the use of the Penman-Monteith equation to make a one-step estimate of crop water requirements. Reluctance to using a one-step estimate results from two outstanding issues, both of which are addressed. First, no method has been yet defined to handle the problem that meteorological variables are commonly available only at 2 m above the ground while, when using the Penman-Monteith equation, they are required at some level above the crop. To resolve this, a blending height is defined in the atmospheric boundary layer (ABL) where meteorological conditions are independent of the underlying crop. Expressions are derived to calculate the aerodynamic resistances to, and the vapor pressure deficit at, the blending height from climate variables at 2 m. Consequently, 2 m climate data can be used in the Penman-Monteith equation, either to estimate transpiration from surface resistance or to calculate surface resistance from measured transpiration. Second, no table of effective values currently exists for the surface resistance of different crops equivalent to that for the crop coefficient. This article calls for field studies to address this need. However, recognizing the need for an interim source of crop-specific surface resistances, a methodology is given for translating the crop coefficient into equivalent surface resistance. To make this translation, it is necessary to specify the relationship between the radiative and aerodynamic energy inputs to evapotranspiration when the crop coefficients were calibrated. Finally, a Penman-Monteith-based, one-step estimation equation is derived that makes proper allowance for the different aerodynamic characteristics of crops in all conditions of atmospheric aridity, and that estimates crop evaporation for any crop of specified height from existing crop coefficients using standard 2 m climate data.",
keywords = "Crop evaporation, Crop water requirements, Crop water use, Energy balance, Evaporation, Evapotranspiration, Irrigation, Irrigation requirements, Penman-Monteith, Reference crop evaporation",
author = "Shuttleworth, {W. James}",
year = "2006",
month = "7",
language = "English (US)",
volume = "49",
pages = "925--935",
journal = "Transactions of the ASABE",
issn = "2151-0032",
publisher = "American Society of Agricultural and Biological Engineers",
number = "4",

}

TY - JOUR

T1 - Towards one-step estimation of crop water requirements

AU - Shuttleworth, W. James

PY - 2006/7

Y1 - 2006/7

N2 - This article provides theoretical analyses that facilitate the use of the Penman-Monteith equation to make a one-step estimate of crop water requirements. Reluctance to using a one-step estimate results from two outstanding issues, both of which are addressed. First, no method has been yet defined to handle the problem that meteorological variables are commonly available only at 2 m above the ground while, when using the Penman-Monteith equation, they are required at some level above the crop. To resolve this, a blending height is defined in the atmospheric boundary layer (ABL) where meteorological conditions are independent of the underlying crop. Expressions are derived to calculate the aerodynamic resistances to, and the vapor pressure deficit at, the blending height from climate variables at 2 m. Consequently, 2 m climate data can be used in the Penman-Monteith equation, either to estimate transpiration from surface resistance or to calculate surface resistance from measured transpiration. Second, no table of effective values currently exists for the surface resistance of different crops equivalent to that for the crop coefficient. This article calls for field studies to address this need. However, recognizing the need for an interim source of crop-specific surface resistances, a methodology is given for translating the crop coefficient into equivalent surface resistance. To make this translation, it is necessary to specify the relationship between the radiative and aerodynamic energy inputs to evapotranspiration when the crop coefficients were calibrated. Finally, a Penman-Monteith-based, one-step estimation equation is derived that makes proper allowance for the different aerodynamic characteristics of crops in all conditions of atmospheric aridity, and that estimates crop evaporation for any crop of specified height from existing crop coefficients using standard 2 m climate data.

AB - This article provides theoretical analyses that facilitate the use of the Penman-Monteith equation to make a one-step estimate of crop water requirements. Reluctance to using a one-step estimate results from two outstanding issues, both of which are addressed. First, no method has been yet defined to handle the problem that meteorological variables are commonly available only at 2 m above the ground while, when using the Penman-Monteith equation, they are required at some level above the crop. To resolve this, a blending height is defined in the atmospheric boundary layer (ABL) where meteorological conditions are independent of the underlying crop. Expressions are derived to calculate the aerodynamic resistances to, and the vapor pressure deficit at, the blending height from climate variables at 2 m. Consequently, 2 m climate data can be used in the Penman-Monteith equation, either to estimate transpiration from surface resistance or to calculate surface resistance from measured transpiration. Second, no table of effective values currently exists for the surface resistance of different crops equivalent to that for the crop coefficient. This article calls for field studies to address this need. However, recognizing the need for an interim source of crop-specific surface resistances, a methodology is given for translating the crop coefficient into equivalent surface resistance. To make this translation, it is necessary to specify the relationship between the radiative and aerodynamic energy inputs to evapotranspiration when the crop coefficients were calibrated. Finally, a Penman-Monteith-based, one-step estimation equation is derived that makes proper allowance for the different aerodynamic characteristics of crops in all conditions of atmospheric aridity, and that estimates crop evaporation for any crop of specified height from existing crop coefficients using standard 2 m climate data.

KW - Crop evaporation

KW - Crop water requirements

KW - Crop water use

KW - Energy balance

KW - Evaporation

KW - Evapotranspiration

KW - Irrigation

KW - Irrigation requirements

KW - Penman-Monteith

KW - Reference crop evaporation

UR - http://www.scopus.com/inward/record.url?scp=33750593932&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33750593932&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:33750593932

VL - 49

SP - 925

EP - 935

JO - Transactions of the ASABE

JF - Transactions of the ASABE

SN - 2151-0032

IS - 4

ER -