Abstract: Apparatus for measuring the real evapotranspiration of a plant cover, for measuring the amount of carbon dioxide exchanged between said plant cover and the atmosphere and for measuring the hydrous state of the ground around the plant cover. The apparatus includes an assembly of terminals, an electronic command and calculation unit, and a unit to store the results calculated by the electronic command and calculation unit. The apparatus permits the calculation of the evapotranspiration by the application of any one of the Bowen ratio method, the simplified direct aerodynamic method, or the simplified combined aerodynamic method.