INFLUENCE OF SEASONALLY DIFFERENT NA STRESS ON VEGETATIVE GROWTH AND YIELD OF THE APPLE CULTIVAR GOLDEN DELICIOUS

The influence of seasonally different sodium stress on the vegetative growth and yield of 'Golden Delicious' apple trees on M26 and M9 was investigated in an outdoor pot experiment (1984-1987). The trees were treated with increased NaCl or Na2SO4 supplies (30/60 meq/l) during the first or second half of the year (early/late treatment). Increased Na supply led to a decrease in trunk growth and leaf dry matter. Salt stress during the first half of the vegetation period led to a more significant reduction in dry substance than during the second half. This difference was more distinct on M9 than on M26. Yield was mainly reduced by high Na supplies during the first half of the year. On M9 this turned out more than on M26. The decrease was determined by reduced fruit weights. The results indicate that salt stress during the first half of the year causes higher damage to the trees than the second. A higher salt tolerance of M26 compared to M9 may be concluded.