Evaluation of alternative methods to calculate evapotranspiration and their impact on soybean yield estimation

Abstract

Despite the several studies comparing methods for evapotranspiration (ETo)estimation, scientific reports demonstrating their use and evaluation when coupled to agrometeorological models have not been analyzed, particularly in regard to the comparison of the estimated results obtained in the modeling with the real production data experimentally obtained in the field. The present study evaluated nine alternative methods to calculate ETo for estimating soybean yield, associated with actual yields obtained in irrigated and non-irrigated fields, at three sowing periods during the 2013/14 crop season in Southern Brazil. All methods were evaluated in relation to the standard Penman–Monteith method. Their performance was measured through regression analysis and statistical coefficients submitted to the Tukey test. ETo values obtained through the alternative methods were used to calculate water balances for soybean, considering irrigated and non-irrigated environments. Theoretical and real potential yields were higher in later sowings. The Priestley–Taylor method was the best to estimate daily ETo alternatively to that recommended by FAO (Penman–Monteith). On the other hand, the alternative method of Thornthwaite–Camargo was the best for estimations at 10-day periods, in all sowing dates. Furthermore, the methods of Thornthwaite–Camargo, Benevides–Lopez, Camargo, and Thornthwaite showed the smallest deviations to estimate ETo (10-day periods) for calculating actual yields (Ya).