Abstract

LOPEZ AVENDANO, Jesús Enrique et al. Evapotranspiration and crop coefficient of bell pepper in Culiacan Valley, Mexico. Terra Latinoam [online]. 2015, vol.33, n.3, pp.209-219. ISSN 2395-8030.

Evapotranspiration is an important component of earth's hydrological cycle and energy balance. Understanding and estimating it is crucial for planning the use of water resources, particularly, efficient use of irrigation water. Thus, the objectives of this study were to apply the method of Eddy Covariance for measuring evapotranspiration (ETc) and determining crop coefficients (Kc) for bell pepper (Capsicum annuum L.) and to improve the accuracy of the FAO-56 method of estimating ETc for this crop. The study was carried out in the Valley of Culiacan, Mexico, from February to April 2014 on 90 ha irrigated with drip irrigation. ETo was calculated using the Penman-Monteith equation. Moreover, to estimate adjusted ETc, adjusted Kc was also used. Adjusted Kc was obtained with quadratic regression carried out with estimated Kc data and the days after transplanting. Several parameters were used for statistical analysis: the Root Mean Square Error (RMSE), the Willmott concordance index (d), the Nash and Sutcliffe efficiency index (E) and the coefficient of determination (R2). The results showed that measured evapotranspiration was 267.6 mm, while it was 363.6 mm when estimated with CE and FAO-56 methods, respectively. This represents a relative error of 35.9%, whereas the adjusted ETc was 261.5 mm. The Kc values for the crop mid-season stage were 0.86, 1.16 and 0.86, whereas for the crop end-stage, they were 0.66, 0.87 and 0.64 with the EC, FAO-56 and adjusted Kc methods, respectively. The statistical values between ETcFAO-56 and ETcCE were E = -13.2, d = 0.51, R2 = 0.56 and RMSE = 1.32 mm d-1. The FAO-56 method overestimated ET measured with the EC method.

Keywords : dual coefficient; FAO-56 method; drip irrigation; eddy covariance system.