Relationships between evapotranspiration of corn, solar radiation and net radiation

Abstract

The evapotranspiration (ET) of corn crop (Zea mays L.) (Pioneer X-307 hibrid) calculated during four years (1976-1980), was related with solar radiation (Rs) and net radiation (Rn) in the different stages and in the cycle of the crop. This trial was conducted in Taquari, Rio Grande do Sul, 29 °48'15" south latitude and 76 m of altitude. Both relations presented the same tendency. They were lower during the early cycle of the crop, increasing progressively with the development of the plants, reaching maximum values during tasseling and silking period. During this period, the relation ET/Rs varied from 0.62 to 0.79 during the four years (with mean of 0.70) while the relation ET/Rn varied from 0.83 to 1.07 (with mean of 0.94). After flowering, there was a decrease in the values of the relations until physiological maturation of crop. The relations ET/Rs and ET/Rn during the cycle of development of the crop, obtained mean values of 0.51 and 0.69, respectively.