Susnoschi, M., Dept. of Vegetable Crops, Agricultural Research Organization, Gilat Experiment Station Negev, 85-280, Israel
Shimshi, D., Dept. of Experimental Physiology and Irrigation, Agricultural Research Organization, Gilat Experiment Station Negev, 85-280, Israel

Five potato cultivars were subjected to water deficits as well as to excess water and to corresponding amounts of nitrogen top dressing (N.t.) applied in the irrigation water. The rates of growth in response to water-N. t. were highest for all cultivars when Kp=1.06 (pan evaporation coefficient) and N.t=173 kg/ha. In the drier treatments (0.87>Kp>0.14 and 127>N.t.>12 kg/ha) and in the wetter treatment (Kp=1.27; N.t.=201 kg/ha), the growth rates decreased. The cultivars differed in their haulm size, especially at Kp=1.0, N.t.=173 kg/ha. At 70 days after planting cv. Cardinal had about half the haulm weight of cv. Désirée. Nevertheless, both cultivars exhibited similar bulking rates. On the other hand, cv. Spunta, which had high bulking rates at the earlier stage of growth, had a marked advantage in yield production in the drier treatments (Kp=0.29-0.14; N.t.=44-12 kg/ha). The maximum leaf area indices (LAI) were obtained at Kp=1.06, N.t.=173 kg/ha and were similar for all cultivars. LAI and leaf area duration (LAD) decreased with increasing water stress. In Cardinal, Désirée, Spunta and cv. Up-to-Date there was a common linear function relating to tuber weigth and to LAD; in cv. Alpha, this function had lower values of tuber weight. © 1985 Kluwer Academic Publishers.