The research was conducted in a greenhouse installed at the experimental farm of the Center for Agrarian Sciences, Federal University of São Carlos, in the city of Araras - SP. The soil of the experimental area is dark red Latosols, dystrophic; moderate A horizon, clay texture. The melons studied were the hybrids Louis and HD 90. The experiment was irrigated by drip irrigation and control accomplished through two weighing lysimeters installed inside the greenhouse. Soil moisture was monitored with a TDR probe and maintained close to field capacity. The climatic information was collected in automatic weather stations installed inside and outside the greenhouse. The reference evapotranspiration (ETo) was estimated by the Penman-Monteith, Penman, Makkink and Class A Pan models. The water consumption measured in the lysimeters was 254.5 mm and 188.6 mm, respectively, for melons Louis and HD 90, corresponding to an average daily consumption of 3.18 mm and 2.35 mm. All models underestimated the ETo estimated by the standard model of Penman-Monteith varying from a minimum of 26.9% in the case of the Penman model up to 74.3% in the Makkink model. The crop coefficients determined by the standard model of Penman-Monteith, here considering the average value of the two types of melon studied, were as follows: early stage: 0.20; intermediate stage: 1.10 and final stage: 0.50.
melon; protected cultivation; load cell
