Cultivar and rootstock response to drip irrigation in sweet cherry tree vigour and start of bearing during the first three years after planting

Fifteen sweet cherry cultivars and three rootstocks were evaluated within three years in two experimental orchards established in the same location in the autumn 2004. In one of them drip irrigation was applied in the periods of insufficient rainfall, i.e. from mid-April to mid-August. This irrigation distinctly increased the vigour of trees that was jointly expressed by trunk-cross-section area, total length of shoots and canopy volume. An increase of tree vigour was the greatest in trees on Mazzard, medium on P-HL-C and the lowest on Gisela 5 rootstocks. The trees on P-HL-C that grew without irrigation similarly as the trees on Gisela 5 grew significantly more vigorously when irrigation was applied. Considerable differences in the response to irrigation were also found among cultivars; it increased the vigour of Halka, Sylvana, Aranka and Burlat more distinctly, whereas the least response to irrigation was recorded in the Horka, Jacinta and Justyna cultivars. The vigour of Regina, Tim and Vanda cultivars grown on P-HL-C rootstock was more extensively increased by irrigation than if they grew on Gisela 5. Flower and fruit sets of irrigated trees were with a few exceptions significantly lower than those of trees without irrigation. Tamara, Sandra and Regina were the most vigorous cultivars in this study, whereas Tim and Skeena had the weakest tree growth. Practical aspects of these findings are briefly discussed.