Calibration and evaluation of mathematical models to calculate reference evapotranspiration in greenhouses

Abstract

With the reference evapotranspiration (ETo) and the Kc of a crop, the volumes of irrigation water and frequency of application are estimated and planned. In Mexico, the area of protected agriculture increases from 20 to 25% annually, 44% are greenhouses and production units less than 0.5 ha predominate, suggesting that they have limited technology. For greenhouses there is no standard method for estimating ETo such as Penman-Monteith for open field. With a Campbell automatic station installed inside a greenhouse on the grounds of the Chapingo Autonomous University, two series of meteorological data were measured. With the first one, the parameters of several models reported in the literature were modified to calculate ETo, some based on temperature (Baier-Robertson, Romanenko and Hargreaves) and others on radiation (Abtew, Jensen-Haise, Caprio, Irmak, Sthepen, Priestley-Taylor and Makkink) and with the second all were evaluated. The ETo obtained by each of the methods with its modified parameters was compared with the ETo calculated with the Penman-Monteith method, determining that the radiation models showed better adjustments than those of temperature. In the evaluation, those based on temperature showed inadequate adjustments with R² less than 0.461 and RSE greater than 0.31 mm d^-1 and those of radiation had R² greater than 0.909 and RSE less than 0.21. The modified Abtew model was the best for estimating ETo in a greenhouse with an R² of 0.947 and an RSE of 0.06 mm d^-1.