Effects of flooding and alluvium deposition on kiwifruit (Actinidia deliciosa) 1. early vine decline

Abstract

Kiwifruit vines are reported to be very sensitive to anaerobic conditions in the root zone, but this has been little studied under orchard conditions. Opportunity to study this extensively arose when, in March 1988, Cyclone Bola caused flooding in kiwifruit orchards near Gisborne, New Zealand. We sought to identify factors responsible for early decline of flooded vines, and strategies to increase vine survival after flooding. Early decline was defined as premature defoliation in the first 11 weeks following the flood. Vine health and soil conditions were monitored at 10 sites. Vines first showed waterlogging damage 3-7 days after the flood, but the proportion of vines affected varied greatly between sites. Over all sites, one third of the vines experienced early decline. One half of these affected vines were still stressed or dead the following spring (October 1988). Early decline was closely associated with feeder root death. Infections by Phytophthora spp. and site-to-site differences in flood conditions showed little relation to the incidence of early decline. A major factor in feeder root death and early vine decline was poor soil structure, which resulted in inadequate drainage, and soil anaerobisis. Vine sensitivity to waterlogging in the field varied greatly, apparently the result of factors such as variations in soil conditions and previous vine vigour. It appears the single most important means of enhancing vine resistance to flood events is to ensure soil structure is well maintained. © Crown copyright 1991.