Impiego di un microlisimetro per la determinazione dell'evapotraspirazione del riso in coltura sommersa

A microlysimeter has been built to determine effective evapotranspiration in flooded rice. The microlysi meter was of the Tomar and O'Toole type subsequently modified. The changes made allow: continuous readings of evapotranspiration during a period varying from four to eight days on a surface of 0,5 m2and high instrument sensitivity. The experimental trial was carried out at S. Lucia (OR) in 1982 using four microlysimeters. The evapotran spiration values were peridically taken within the tillering and physiological maturity phases. The evaluation of the regression between evapotranspiration and evaporation from a class «A» PAN tank permitted calculation of the evapotranspiration during the whole biological cycle of the crop. The total vo lume of evapotranspiration water during the cultural cycle obtained by adding up the measured and est imated values was 7.692 m3/ha whereas the volume of water really delivered In the rice-field was 9.670 m3/ha. The difference between the previous values (about 2000 m3/ha) stands for losses due to drying off and deep percolation .