The final tuber yield response to irrigation regime differed in relation to cultivar, as
demonstrated by the significance of the irrigation regime x cultivar interaction (Fig. 8).
Irrespective of planting date, decreasing the water supply caused a decrease in tuber yield of
21% in Spunta but only 3%in Sieglinde. On the other hand, the yield differences between the
two cultivars (in favour of Spunta), were 16% and not significant in plots irrigated with 50%
ETM, but were 48% and significant in plots irrigated with 100% ETM (Fig. 8).