عنوان مقاله [English]
The purpose of this research was to investigate the response of evapotranspiration components of maize to different levels of water stress. This research was done as a completely randomized design. Treatments included the irrigation at four levels of 100(I0), 80(I1), 60(I2) and 40(I3) percent of the crop water requirement. Daily crop evapotranspiration was measured based on soil water balance in mini-lysimeter. To separate the amounts of evapotranspiration components, were used mini-lysimeters with and without mulch covering on the soil surface. In the all of growth stages, the amounts of evapotranspiration, transpiration and evaporation were estimated equal to 424.5, 267.3 and 157.2 mm (in I0), 405.8, 245.4 and 160.4 mm (in I1), 360.5, 194.4 and 166.1 mm (in I2) and 303.7, 125.5 and 178.2 mm (in I3) respectively. The results showed that from I0 to I3, the amounts of evapotranspiration and transpiration decreased to 28.4% and 53% respectively, and the evaporation amount increased to 13.4%. Therefore, in the evapotranspiration parameter, the transpiration portion was decreased to 35% and the evaporation portion was increased to 35%. The most amount of transpiration occurred in the developmental period and the most amount of evaporation occurred in the initial and final growth stages. But the highest response of transpiration and evaporation to water stress occurred in the middle period, in which transpiration decreased to 69% and evaporation increased to 253%. The existence of sensitive stages in the middle period of growth, caused the water stress to have the most effect. The results showed that in the low irrigation, in addition to reducing the transpiration, there is an increase in the portion of evaporation. Therefore, covering the soil surface and applying the suitable level of water stress in irrigation management, will be effective factors for increasing the water use efficiency.