Fiel d experiments were carried out at the La Platina Experimental Station (INIA, Santiago), during 1982/83 and 1983/84. Eleven water regimes were tried, using a simple Iine sprinkler system, proposed by Hanks et al (1976). Crop evapotranspiration (ET) was determined using the soil water balance method; soil moisture was mea sured with a neutron probe. A linear relation between yield and total extracted water was found. Total ET amounted to 5,200 m3 /ha.
The relative reduction in yield in relation to the relative change in ET was as follows:
1 - Y / Ym = Ky (1 - ET / ETm)
Where Ky was 1.14 and 1.23 for each year, with a mean of 1.18; Y = yield obtained; Ym = maximum yield; and ETm = maximum evapotranspiration.