Francisco Córdova Palma1

A experiment was made to determine the evapotranspiración (ET) of corn at La Platina (Santiago, Chile) during three growing seasons of this annual row crop. a relationship between ET data and the water losses from a open pan evaporation (EV) was made. It was found that the mean regression coefficients value was 0.70.
The seasonal variations of ET/EV values indicated that the water use by corn is closely related with corn development. For a period of 14-16 days (at silking stage) the ratio of evapotranspiration to open pan evaporation was 0.91. Before this period the ratio increases with increasing leaf area index and with increasing shading of the ground. Afterwards the ratio declines with declining physiological activity of plants.
To estimate water requirements on a certain period basis, the appropiate ratio is simply multiplied by the mean pan evaporation values for the considered period.

1Ing. Agr. Centro Suelos-Riego. Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.