African Journal of
Agricultural Research

  • Abbreviation: Afr. J. Agric. Res.
  • Language: English
  • ISSN: 1991-637X
  • DOI: 10.5897/AJAR
  • Start Year: 2006
  • Published Articles: 6842

Full Length Research Paper

Use of atmometers to estimate reference evapotranspiration in Arkansas

Lamine DIOP
  • Lamine DIOP
  • UFR S2ATA, Sciences Agronomiques, d’Aquaculture et des Technologies Agroalimentaires, Université Gaston Berger (UGB), BP 234-Saint Louis, Sénégal.
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Ansoumana BODIAN
  • Ansoumana BODIAN
  • Laboratoire Leïdi, Dynamique des Territoires et Développement, Université Gaston Berger (UGB), BP 234-Saint Louis, Sénégal.
  • Google Scholar
Dior DIALLO
  • Dior DIALLO
  • Département Génie Rural, Ecole Nationale Supérieure d’Agriculture (ENSA), Université de Thiès (UT), BP 296/A-Thiès, Sénégal.
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  •  Received: 22 August 2015
  •  Accepted: 09 October 2015
  •  Published: 26 November 2015

Abstract

Evapotranspiration (ET) data from atmometers were compared against evapotranspiration estimated by the FAO-56 Penman-Monteith equation, recommended method, in order to evaluate the accuracy of atmometers. Measurements by 3 atmometers with grass cover and 3 atmometers with alfalfa cover were compared, for one growing season, to Penman Monteith based grass and alfalfa equation–(ET0_PM and ETr_PM,, respectively). Comparison between cumulative Evapotranspiration measured by atmometers and ET0_PM or ETr_PM showed that Atmometers, for both grass and alfalfa, underestimate evapotranspiration by 12.5-21 and 15% respectively. The three Atmometers with alfalfa cover  give the same cumulative value (636 mm) compared to the atmometers with grass cover  which exhibit different results (atmometers 1 and 3 (467 mm) and atmometers 2 gives 419 mm).  Correlation between ET from atmometers and ETr_PM or ET0_PM estimates were generally good. Evaporation from atmometers with alfalfa cover showed the highest correlation to ETr_PM (R2 varying from 0.68 to 0.72) whereas evaporation from atmometers with grass cover present the lowest correlation (R2ranges from 0.49 to 0.68). The results indicated that with the proper regression equation and a good calibration, atmometers could be used to estimate ET for crop water requirement where evapotranspiration estimates are not available from weather stations.

 

Key words: Atmometer, evaporation, evapotranspiration, irrigation, Penman-Monteith equation.