| Sumario: | The experiments analyzed in this report. wern conducted in a gypseos clay soil at the
"Instituto de Suelos y Riego" Fxperimental Farm, Guaymallén, Mendoza, Argentine Republic.
A wheat crop was soed about the middle of november; and the experiment
followed until the beginning of heading stage. Every 7 das, plants were digged up, and
height of the plauts H, depth of root zone D, and dry weigth of' the
plants Ps, were determined.
The crop was periodically irrigated. ln accordance with the dates of digging up the
plants, actual evapotranspiration was obtained by measuring soil water content, in the soil
layer reached by the plant roots.
Relative evapotraspiration Ea/Ep, was stndied as a function of diferent expressions of
plant growth : H, D and Ps. From the analysis of that relationships during « the great growth
rate period», may be deducted that relative evapotranspiration changes potentially or
exponentially with H and with P8,
and linearly with D.
Actual to potential evapotranspiration ratio increases with D, even when soil
water potential reaches very low vales in the root zone. This is due to the fact of the
increasing volume of soil explored by the roots, and the easy availability
of water for roots in their downwards growth.
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