To verify the efficiency of the evapotranspiration reference methods (ETo), it is necessary to contrast with the standard method. This work has the purpose to compare three methods of ETo estimation: Solar Radiation (RS), Makkink (MAK) and a Class A tank (TCA) method with Penman-Monteith method (PM), in two phases of citrus growth, working with biweekly medium data for the winter-spring and summer-autumn periods. The research was developed in a citrus farm, in Araraquara - SP, Brazil, where it was installed an automated meteorological station and a Class A tank. Through a system of data acquisition, measures of the global solar radiation, radiation balance, temperature of the air, relative humidity of the air and speed of the wind, were obtained. The linear regression analysis shows that the TCA method can be fitted by, y = bx, where y represents EToPM and x represents EToTCA. For the others analyzed methods we found the model y = bx + a. The results of this study indicate that the TCA method overestimated ETo 26% in the summer-autumn period and 24% in the winter-spring period. The MAK method, underestimated ETo in the two analyzed periods, while the RS method overestimated ETo.
irrigation; citrus; evapotranspiration reference
