Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data
Inaccurate crop coefficients are major contributing sources of uncertainty that lead to inefficient use of limited available water resources. Understanding the need to improve water use efficiency in South Africa’s fruit industry, this study evaluated the method of deriving crop coefficients develop...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2023-08-01
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| Series: | Agricultural Water Management |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S0378377423002548 |
| _version_ | 1797448118310010880 |
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| author | Munashe Mashabatu Zanele Ntshidi Sebinasi Dzikiti Nebojsa Jovanovic Timothy Dube Nicky J. Taylor |
| author_facet | Munashe Mashabatu Zanele Ntshidi Sebinasi Dzikiti Nebojsa Jovanovic Timothy Dube Nicky J. Taylor |
| author_sort | Munashe Mashabatu |
| collection | DOAJ |
| description | Inaccurate crop coefficients are major contributing sources of uncertainty that lead to inefficient use of limited available water resources. Understanding the need to improve water use efficiency in South Africa’s fruit industry, this study evaluated the method of deriving crop coefficients developed by Allen and Pereira (2009) over a variety of irrigated fruit tree crops. Detailed data of transpiration, evapotranspiration and weather variables measured using the heat ratio method, eddy covariance method and automatic weather stations, were collected from a water research funding body established by the South African government. This study adjusted the stomatal sensitivity function (Fr) in the model by replacing the ratio of the leaf resistance (rl) to the standard leaf resistance of a reference crop (100 sm−1) with rl/α where α is a resistance parameter for the specific crop. The resistance parameter was solved accordingly for each fruit type. Respective unique α values were obtained as: macadamia nuts (200 sm−1), citrus (50 s m−1), peaches (20 s m−1) and pecans (20 s m−1). These unique values were used to simulate basal and single crop coefficients that produced satisfactory results when compared to the actual measured values. Overly, no unique standard α value exists for most tree crops although a value close to 20 sm−1 may give reasonable estimates for pome and stone fruit. Crop coefficients derived using locally measured data were standardised and tabulated in a format that facilitates their transferability between sites. However, there is still a need to acquire crop specific information to parameterize α and improve accuracies. |
| first_indexed | 2024-03-09T14:05:50Z |
| format | Article |
| id | doaj.art-615cd8cb37de419abed5e847942948db |
| institution | Directory Open Access Journal |
| issn | 1873-2283 |
| language | English |
| last_indexed | 2024-03-09T14:05:50Z |
| publishDate | 2023-08-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Agricultural Water Management |
| spelling | doaj.art-615cd8cb37de419abed5e847942948db2023-11-30T05:05:35ZengElsevierAgricultural Water Management1873-22832023-08-01286108389Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height dataMunashe Mashabatu0Zanele Ntshidi1Sebinasi Dzikiti2Nebojsa Jovanovic3Timothy Dube4Nicky J. Taylor5Department of Earth Sciences, University of the Western Cape, Capetown, South Africa; Corresponding author.Council for Scientific and Industrial Research, Stellenbosch, South AfricaDepartment of Horticulture, Stellenbosch University, Stellenbosch, South AfricaDepartment of Earth Sciences, University of the Western Cape, Capetown, South AfricaDepartment of Earth Sciences, University of the Western Cape, Capetown, South AfricaDepartment of Plant and Soil Sciences, University of Pretoria, South AfricaInaccurate crop coefficients are major contributing sources of uncertainty that lead to inefficient use of limited available water resources. Understanding the need to improve water use efficiency in South Africa’s fruit industry, this study evaluated the method of deriving crop coefficients developed by Allen and Pereira (2009) over a variety of irrigated fruit tree crops. Detailed data of transpiration, evapotranspiration and weather variables measured using the heat ratio method, eddy covariance method and automatic weather stations, were collected from a water research funding body established by the South African government. This study adjusted the stomatal sensitivity function (Fr) in the model by replacing the ratio of the leaf resistance (rl) to the standard leaf resistance of a reference crop (100 sm−1) with rl/α where α is a resistance parameter for the specific crop. The resistance parameter was solved accordingly for each fruit type. Respective unique α values were obtained as: macadamia nuts (200 sm−1), citrus (50 s m−1), peaches (20 s m−1) and pecans (20 s m−1). These unique values were used to simulate basal and single crop coefficients that produced satisfactory results when compared to the actual measured values. Overly, no unique standard α value exists for most tree crops although a value close to 20 sm−1 may give reasonable estimates for pome and stone fruit. Crop coefficients derived using locally measured data were standardised and tabulated in a format that facilitates their transferability between sites. However, there is still a need to acquire crop specific information to parameterize α and improve accuracies.http://www.sciencedirect.com/science/article/pii/S0378377423002548Basal crop coefficientsEvapotranspirationSingle crop coefficientTranspiration |
| spellingShingle | Munashe Mashabatu Zanele Ntshidi Sebinasi Dzikiti Nebojsa Jovanovic Timothy Dube Nicky J. Taylor Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data Agricultural Water Management Basal crop coefficients Evapotranspiration Single crop coefficient Transpiration |
| title | Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data |
| title_full | Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data |
| title_fullStr | Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data |
| title_full_unstemmed | Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data |
| title_short | Deriving crop coefficients for evergreen and deciduous fruit orchards in South Africa using the fraction of vegetation cover and tree height data |
| title_sort | deriving crop coefficients for evergreen and deciduous fruit orchards in south africa using the fraction of vegetation cover and tree height data |
| topic | Basal crop coefficients Evapotranspiration Single crop coefficient Transpiration |
| url | http://www.sciencedirect.com/science/article/pii/S0378377423002548 |
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