Technical Note: On the Matt–Shuttleworth approach to estimate crop water requirements

Abstract. The Matt–Shuttleworth method provides a way to make a one-step estimate of crop water requirements with the Penman–Monteith equation by translating the crop coefficients, commonly available in FAO publications, into equivalent surface resistances. The methodology is based upon the theoretical relationship linking crop surface resistance to crop coefficient and involves the simplifying assumption that the reference crop evapotranspiration (ET0) is equal to the Priestley–Taylor estimate with a fixed coefficient of 1.26. This assumption, used to eliminate the dependence of surface resistance on certain weather variables, is questionable: numerical simulations show that it can lead to substantial differences between the true value of surface resistance and its estimate. Consequently, the basic relationship between surface resistance and crop coefficient, without any assumption, appears to be more appropriate for inferring crop surface resistance, despite the interference of weather variables.

Download Full-text

Comment on "Technical Note: On the Matt–Shuttleworth approach to estimate crop water requirements" by Lhomme et al. (2014)

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-5367-2014 ◽

2014 ◽

Vol 11 (5) ◽

pp. 5367-5375

Author(s):

W. J. Shuttleworth

Keyword(s):

United Nations ◽

Technical Note ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

The United Nations ◽

United Nations Food ◽

Simple Equations

Abstract. It is clear from Lhomme et al. (2014) that aspects of the explanation of the Matt–Shuttleworth approach can generate confusion. Presumably this is because the description in Shuttleworth (2006) was not sufficiently explicit and simple. This paper explains the logic behind the Matt–Shuttleworth approach clearly, simply and concisely. It shows how the Matt–Shuttleworth can be implemented using a few simple equations and provides access to ancillary calculation resources that can be used for such implementation. If the crop water requirement community decided that it is preferable to use the Penman–Monteith equation to estimate crop water requirements directly for all crops, the United Nations Food and Agriculture Organization could now update Irrigation and Drainage Paper 56 using the Matt–Shuttleworth approach by deriving tabulated values of surface resistance from Table 12 of Allen et al. (1998), with the estimation of crop evaporation then being directly made in a one-step calculation using an equation similar to that already recommended by the United Nations Food and Agriculture Organization for calculating reference crop evaporation.

Download Full-text

Comment on "Technical Note: On the Matt–Shuttleworth approach to estimate crop water requirements" by Lhomme et al. (2014)

Hydrology and Earth System Sciences ◽

10.5194/hess-18-4403-2014 ◽

2014 ◽

Vol 18 (11) ◽

pp. 4403-4406 ◽

Cited By ~ 2

Author(s):

W. J. Shuttleworth

Keyword(s):

United Nations ◽

Technical Note ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

The United Nations ◽

United Nations Food ◽

Simple Equations

Abstract. It is clear from Lhomme et al. (2014) that aspects of the explanation of the Matt–Shuttleworth approach can generate confusion. Presumably this is because the description in Shuttleworth (2006) was not sufficiently explicit and simple. This paper explains the logic behind the Matt–Shuttleworth approach clearly, simply and concisely. It shows how the Matt–Shuttleworth can be implemented using a few simple equations and provides access to ancillary calculation resources that can be used for such implementation. If the crop water requirement community decided that it is preferable to use the Penman–Monteith equation to estimate crop water requirements directly for all crops, the United Nations Food and Agriculture Organization could now update Irrigation and Drainage Paper 56 using the Matt–Shuttleworth approach by deriving tabulated values of surface resistance from Table 12 of Allen et al. (1998), with the estimation of crop evaporation then being directly made in a one-step calculation using an equation similar to that already recommended by the United Nations Food and Agriculture Organization for calculating reference crop evaporation.

Download Full-text

Estimation of crop water requirements: extending the one-step approach to dual crop coefficients

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-4933-2015 ◽

2015 ◽

Vol 12 (5) ◽

pp. 4933-4963 ◽

Cited By ~ 1

Author(s):

J. P. Lhomme ◽

N. Boudhina ◽

M. M. Masmoudi ◽

A. Chehbouni

Keyword(s):

Surface Resistance ◽

Crop Coefficient ◽

Soil Surface ◽

Stomatal Resistance ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

One Step ◽

Crop Coefficients ◽

Monteith Equation

Abstract. Crop water requirements are commonly estimated with the FAO-56 methodology based upon a "two-step" approach: first a reference evapotranspiration (ET0) is calculated from weather variables with the Penman–Monteith equation; then ET0 is multiplied by a tabulated crop-specific coefficient (Kc) to determine the water requirement (ETc) of a given crop under standard conditions. This method has been challenged to the benefit of a "one-step" approach, where crop evapotranspiration is directly calculated from a Penman–Monteith equation, its surface resistance replacing the crop coefficient. Whereas the transformation of the two-step approach into a one-step approach has been well documented when a single crop coefficient (Kc) is used, the case of dual crop coefficients (Kcb for the crop and Ke for the soil) has not been treated yet. The present paper examines this specific case. Using 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. This equation has the basic form of the Penman–Monteith equation, but its surface resistance is calculated as the parallel sum of a foliage resistance (replacing Kcb) and a soil surface resistance (replacing Ke). We also show that the foliage resistance, which depends on leaf stomatal resistance and leaf area, can be inferred from the basal crop coefficient (Kcb) in a way similar to the Matt–Shuttleworth method.

Download Full-text

Estimation of crop water requirements: extending the one-step approach to dual crop coefficients

Hydrology and Earth System Sciences ◽

10.5194/hess-19-3287-2015 ◽

2015 ◽

Vol 19 (7) ◽

pp. 3287-3299 ◽

Cited By ~ 3

Author(s):

J. P. Lhomme ◽

N. Boudhina ◽

M. M. Masmoudi ◽

A. Chehbouni

Keyword(s):

Surface Resistance ◽

Crop Coefficient ◽

Soil Surface ◽

Stomatal Resistance ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

One Step ◽

Crop Coefficients ◽

Monteith Equation

Abstract. Crop water requirements are commonly estimated with the FAO-56 methodology based upon a two-step approach: first a reference evapotranspiration (ET0) is calculated from weather variables with the Penman–Monteith equation, then ET0 is multiplied by a tabulated crop-specific coefficient (Kc) to determine the water requirement (ETc) of a given crop under standard conditions. This method has been challenged to the benefit of a one-step approach, where crop evapotranspiration is directly calculated from a Penman–Monteith equation, its surface resistance replacing the crop coefficient. Whereas the transformation of the two-step approach into a one-step approach has been well documented when a single crop coefficient (Kc) is used, the case of dual crop coefficients (Kcb for the crop and Ke for the soil) has not been treated yet. The present paper examines this specific case. Using 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. This equation has the basic form of the Penman–Monteith equation but its surface resistance is calculated as the parallel sum of a foliage resistance (replacing Kcb) and a soil surface resistance (replacing Ke). We also show that the foliage resistance, which depends on leaf stomatal resistance and leaf area, can be inferred from the basal crop coefficient (Kcb) in a way similar to the Matt–Shuttleworth method.

Download Full-text

Remote Sensing Derived Crop Coefficient for Estimating Crop Water Requirements for Irrigated Sorghum in the Gezira Scheme, Sudan

Journal of Environmental Informatics ◽

10.3808/jei.200700099 ◽

2007 ◽

Vol 10 (1) ◽

pp. 47-54 ◽

Cited By ~ 5

Author(s):

B.A. Bashir

Keyword(s):

Remote Sensing ◽

Crop Coefficient ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements

Download Full-text

Estimation of the Evapotranspiration and Crop Coefficients of Bell Pepper Using a Removable Weighing Lysimeter: A Case Study in the Southeast of Spain

Sustainability ◽

10.3390/su13020747 ◽

2021 ◽

Vol 13 (2) ◽

pp. 747

Author(s):

Laura Ávila-Dávila ◽

José Miguel Molina-Martínez ◽

Carlos Bautista-Capetillo ◽

Manuel Soler-Méndez ◽

Cruz Octavio Robles Rovelo ◽

...

Keyword(s):

Research Work ◽

Bell Pepper ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Food And Agriculture ◽

Food And Agriculture Organization ◽

Precise Knowledge ◽

Crop Coefficients ◽

Weighing Lysimeter

Water use efficiency is essential in semiarid regions of Spain, and it can be achieved through a precise knowledge of the real crop water requirements (CWR). The Food and Agriculture Organization of the United Nations (FAO) offers standardized crop coefficients to establish the CWR. However, these coefficients can change due to different conditions, such as climatic variations and cultivation practices. In this work, the evapotranspiration (ETClys) and crop coefficients (KClys) of bell pepper were obtained with a compact removable weighing lysimeter between February and August for two crop seasons (2019 and 2020). ETClys was determined from the water balance, and the KClys values were determined as the ratio of the crop evapotranspiration, measured on the removable weighing lysimeter, and the reference evapotranspiration. The KClys average values for the bell pepper in the initial, middle, and final stages were 0.57, 1.06, and 0.80, respectively. KC regression models were obtained as a function of the fraction thermal units, achieving a maximum correlation of 0.67 (R2). In general, the KC values obtained in this research work were lower in the initial and in the final stages and larger in the middle stage in comparison with the FAO-56 values and other research works values in semiarid conditions. The bell pepper yield increased by 7.72% in 2019 and by 3.49% in 2020 compared to the yield reported by the Ministry of the Environment and Rural and Marine Areas of the Spanish Government in 2019 and with a minimum water loss through drainage. The results in this work can help farmers to determine the crop water requirements and to improve the system efficiency in semiarid locations with similar conditions to those in the study.

Download Full-text