EVAPOTRANSPIRATION OF CORN AS FUNCTION OF THE ATMOSPHERIC EVAPORATIVE DEMAND AND PLANT GROWTH

Abstract

The high sensibility of maize crops to water deficits, mainly during the flowering period, makes necessary precise data in terms of water necessity, for several purposes of applications. With the objective to quantify the evapotranspiration throughout the maize crop cycle, at different atmospheric conditions, a field experiment was carried out from 1993/94 to 1996/97, at the Estação Experimental Agronômica of UFRGS, in Eldorado do Sul, Brazil. It was used an early hybrid (Pioneer 3230), sowed at the end of October, in a stand of around 67 thousands plants per hectare. The crop maize maximum evapotranspiration was measured in a weighing lysimeter, located in the center of a 0,54ha homogeneously cropped area. An average ETm of 656mm for the entire crop cycle was obtained, ranging from 575 to 732mm during the four-years period. This variation was attributed, mainly, to differences in the atmospheric evaporative demand. Variations in ETm throughout the crop cycle were also observed in a similar pattern, with minimum values at the beginning of the plant growth, increasing according to the leaf area index, up to maximum values during the flowering stages, and decreasing at the end of the crop cycle.