Performance de modelos na estimativa da evapotranspiração do feijão (Phaseolus vulgaris L.) no cerrado.

Abstract

Bean producers from the brazilian Cerrado region have only one technology for the irrigation handling, the measurement of the water tension in the soil though the use of tensiometers. Although this methodology has high potential of use, it has not been widely adopted by the producers. Thus, the utilization of models to evapotranspiration estimate has shown to be applicable to the Cerrado region; however, the use of these models, without a previous evaluation, can result in the obtaining of imprecise estimates. So, this paper aims to evaluate the performance of six models to evapotranspiration estimate of black bean crop in the dry season of the brazilian Cerrado region. It also aims to give adjusted models to evapotranspiration estimate to the producers which give a handling efficient to the agricultural irrigated system of the Cerrado region. The evapotranspiration of the black bean crop was measured with the use of a weighting lysimeter. The experiment was carried in the Brazilian Agricultural Research Corporation (Embrapa Cerrados), located in Planaltina, DF, Brazil. When estimated with crop coefficient, determined in the research (kco), The original Penman, Penman-Monteith and Jensen-Haise models presented an excellent performance for estimating evapotranspiration; being like this, capable to the irrigation handling. Otherwise, Penman- FAO model resulted in values overestimated in 16,97% while Chistiansen-Hargreaves and Thornthwaite-Camargo models resulted in values underestimated in -11,78% and -25,24%, respectively. In addition, results of this research showed that Penman-FAO (kcD) model with an adjusted wind function J/(uj=2,0(l+0,864u2)] can be applied confidently. Also it was observed, that Chistiansen-Hargreaves model (kcD) with So = 0,5, improved widely its estimates.