EFFECT OF IRRIGATION AND NITROGEN-FERTILIZATION ON AGRONOMICAL TRAILSOF JERUSALEM-ARTICHOKE (HELIANTHUS-TUBEROSUS L)

The aim of this study was to determine the effects of irrigation and n itrogen application on agronomically important traits of Jerusalem art ichoke (Helianthus tuberosus L.). Early and late maturing genotypes, f ive in each case, were investigated in 1988 and 1989 under two levels of water supply (unirrigated and irrigated) and two levels of nitrogen supply (70 and 140 kg N ha-1) on a light sandy soil in Braunschweig-V olkenrode. Although the genotypes differed in the magnitude of their r esponses to higher levels of water and nitrogen supply, the direction of these changes were generally the same. In both years irrigation res ulted in a considerable increase in plant height, tuber number, tuber weight and haulm yield. The tuber yield increased under irrigation by 39 %. In contrast to irrigation the additional supply of nitrogen did not cause an increase in tuber yield. However, the number of tubers pe r plant increased by 13 % and die mean tuber weight decreased by 12 %.