Assessment of the CROPWAT 8.0 software reliability for evapotranspiration and crop water requirements calculations

AbstractThe results of the study devoted to assessment of accuracy and reliability of the CROPWAT 8.0 software application calculations of the evapotranspiration and crop water requirements are represented in the article.The study was based on the results of the perennial field experiments, conducted during the period from 2012 to 2017 at the irrigated lands of the South of Ukraine with different crops, namely: sweet corn, grain corn, soybean, sorghum. We assessed accuracy of the CROPWAT 8.0 software application by the comparison of the calculated values with the real ones. We determined considerable differences between the calculated crops evapotranspiration values and crops irrigation requirements and the real ones obtained in the field experiments. The difference was the most essential in case of the drip-irrigated sweet corn crop and averaged to 46.05% for evapotranspiration and 89.20% for irrigation water requirements, correspondingly. Overhead sprinkler irrigated crops are likely to be more suitable for accurate evapotranspiration prediction by using the CROPWAT 8.0. The slightest discrepancy between the calculated and actual values of the studied parameters were determined on the overhead sprinkler irrigated grain corn crops, where the differences averaged just to 15.86% for evapotranspiration and 41.63% for irrigation norm. The results of the study gave us an opportunity to conclude that CROPWAT 8.0 software application should not be used without previous calibration and adjustment of the crop coefficients for the concrete agricultural production conditions.

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Estimation of crop water requirements in arid region using Penman–Monteith equation with derived crop coefficients: a case study on Acala cotton in Sudan Gezira irrigated scheme

Agricultural Water Management ◽

10.1016/s0378-3774(99)00077-3 ◽

2000 ◽

Vol 45 (2) ◽

pp. 203-214 ◽

Cited By ~ 41

Author(s):

A.W Abdelhadi ◽

Takeshi Hata ◽

Haruya Tanakamaru ◽

Akio Tada ◽

M.A Tariq

Keyword(s):

Arid Region ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Crop Coefficients ◽

Monteith Equation ◽

Sudan Gezira

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Weighing Lysimeters for the Determination of Crop Water Requirements and Crop Coefficients

Applied Engineering in Agriculture ◽

10.13031/2013.22256 ◽

2006 ◽

Vol 22 (6) ◽

pp. 851-856 ◽

Cited By ~ 24

Author(s):

T. Marek ◽

G. Piccinni ◽

A. Schneider ◽

T. Howell ◽

M. Jett ◽

...

Keyword(s):

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Crop Coefficients

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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.

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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.

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Standard single and basal crop coefficients for vegetable crops, an update of FAO56 crop water requirements approach

Agricultural Water Management ◽

10.1016/j.agwat.2020.106196 ◽

2021 ◽

Vol 243 ◽

pp. 106196

Author(s):

L.S. Pereira ◽

P. Paredes ◽

R. López-Urrea ◽

D.J. Hunsaker ◽

M. Mota ◽

...

Keyword(s):

Vegetable Crops ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Crop Coefficients

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Standard single and basal crop coefficients for field crops. Updates and advances to the FAO56 crop water requirements method

Agricultural Water Management ◽

10.1016/j.agwat.2020.106466 ◽

2021 ◽

Vol 243 ◽

pp. 106466

Author(s):

L.S. Pereira ◽

P. Paredes ◽

D.J. Hunsaker ◽

R. López-Urrea ◽

Z. Mohammadi Shad

Keyword(s):

Crop Water ◽

Water Requirements ◽

Field Crops ◽

Crop Water Requirements ◽

Crop Coefficients

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Crop water requirements and crop coefficients for jute mallow (Corchorus olitorius L.) using the SIMDualKc model and assessing irrigation strategies for the Syrian Akkar region

Agricultural Water Management ◽

10.1016/j.agwat.2021.107038 ◽

2021 ◽

Vol 255 ◽

pp. 107038

Author(s):

Hanaa Darouich ◽

Razan Karfoul ◽

Tiago B. Ramos ◽

Ali Moustafa ◽

Baraa Shaheen ◽

...

Keyword(s):

Corchorus Olitorius ◽

Crop Water ◽

Water Requirements ◽

Crop Water Requirements ◽

Crop Coefficients

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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.

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

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-4217-2014 ◽

2014 ◽

Vol 11 (4) ◽

pp. 4217-4233 ◽

Cited By ~ 2

Author(s):

J. P. Lhomme ◽

N. Boudhina ◽

M. M. Masmoudi

Keyword(s):

Surface Resistance ◽

Crop Coefficient ◽

Technical Note ◽

Crop Water ◽

Weather Variables ◽

Water Requirements ◽

Crop Water Requirements ◽

True Value ◽

Basic Relationship ◽

Crop Coefficients

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.

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