Comparison of Reference Evapotranspiration Estimates Obtained by Different Methods in Relation to the Penman-Montheith Method in Cerrado Environment, Brazil

Abstract

Water is the most limiting resource for crop production, however, erroneous estimates of the amount needed to be applied can increase production costs, influence plant nutrition and contaminate the ecosystem. Thus, the objective of this work was to compare the values of Et0 obtained by the methods of Blaney-Criddle, solar radiation and Ivanov with the values resulting from the use of Penman-Monteith method in cerrado environment, Brazil. To estimate evapotranspiration values were used the daily data of the maximum and minimum temperatures, wind speed, amount of daylight hours and relative humidity of the years of 2010 and 2011. To compare the estimated values, the parameters of the regression equation a and b, coefficient of determination (r2), correlation coefficients (r), agreement (d) and confidence (c) were considered. Based on the Penman-Monteith method, it was verified that all the other methods evaluated overestimate the values of Et0 during the whole evaluated period. Despite this, it was founded a good correlation between the Blaney-Criddle method and the Penman-Montheith method. The solar radiation and Ivanov methods presented low coefficient of determination when compared to the PNM method. It was concluded that the reference evapotranspiration, on a daily scale, can be quantified using the Blaney-Criddle method instead of the Penman-Monteith method. Furthermore, the solar radiation and Ivanov methods, despite the good agreement and performance indexes, present the greatest distortions during the year.