EFFECTS OF SOIL AERATION ON ROOT DEMOGRAPHY IN KIWIFRUIT

Kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) vines are usually very sensitive to soil aeration stress in the laboratory and field. However, at some sites previously vigorous vines have shown no foliar symptoms of stress despite waterlogging for up to 7 days. This research attempted to explain such anomalies through intensive study of root demography and sod aeration using a rhizotron. One previously vigorous vine was waterlogged by continuous irrigation for 12 days, another was lightly irrigated twice over the same period. Both vines showed a marked turnover of feeder roots, but net losses were much greater on the waterlogged vine. Roots on die waterlogged vine were rapidly killed as soil aeration became impaired; c. 65% of the initial root length died. However, this vine showed no signs of stress above ground. Our results suggest some healthy kiwifruit vines have many more roots than necessary for water uptake under normal conditions. Such vines can survive waterlogging stresses which kill a large proportion of their root system.