ABSTRACT
This research was performed under field conditions and its main purpose was to determine the maximum (ETm) and the atual evapotranspiration (ETr) and establish the sensibility factor (ky) to the water deficit of the watermelon ( Citrillus lanatus Thumb. Mansf.) cultivar "Crimson Sweet". The experiment was conducted in the district of Canindé, CE. Eight treatments with four replications were used, adopting a randomized block design. The treatments were defined according to the time of water deficit induction and ky was obtained through the relation between the reduction of relative efficiency (1 - yr / ym) and the deficit of relative evapotranspiration (1 - ETr / ETm). The maximum and actual evapotranspiration of watermelon were calculated by the method of water balance in a controlled soil volume, in a field which appeared reliable for the determination of the crop water consumption. The ky varied in each period, in the following decreasing order: flowering, fruit development and vegetative.
Key words:
Citrullus lanatus; water balance; evapotranspiration