The author wants to express his thanks and appreciation to Miss D. M. Dwyer for general assistance and analyses of the samples.

Distribution and translocation of spring-applied nitrogen (N) were quantified for two-year-old Chenin blanc grapevines grown in sand culture. Vines were labeled with 15N over a four-week period stretching from the end of bloom to the end of rapid shoot growth. From this stage onwards, vines were fed unlabeled KNO 3, and entire vines were sampled eight times over a period of 11 months. Five samples were taken in the second and three during the third growing season. At the first sampling date (one week after the end of labeling), 55% of the labeled N was found in the vegetative growth, 20% in the bunches, and 25% in the permanent structure. Up to harvest, the total N content of shoots and leaves did not decrease, but the amount of labeled N showed losses of 48% and 21%, respectively. This indicated the importance of these organs as transitional reservoirs for N absorbed during late spring. Spring-applied N was also translocated from the permanent structure, resulting in the bunches containing 45% of the labeled N at harvest. Nearly 40% of the spring-applied N still present in the leaves at harvest was translocated to the shoots and the permanent structure during leaf senescence. At the end of dormancy, the fine roots, rootstock-and scion trunks contained similar concentrations of labeled N, but the rootstock trunk showed a larger proportion of soluble N. At the start of the third growing season, new growth utilized reserve N more readily from the permanent wood than from the roots, but roots played an important role at a later stage, i.e., during bloom. The annual turnover of N for the whole vine appeared to be in the order of 80%, which is considerably higher than that of some other deciduous crops.

for general assistance, preparation of samples and determination of P. 2. Miss A. E. Theron for determination of K, Ca and Mg.

Characteristics of Chardonnay and Pinot noir vines on Richter 99 (99R), Richter 110 (110R), Ruggeri 140 (140Ru)and SO4 rootstocks were assessed over six consecutive seasons in a factorial field trial on an Avalon soil in Stellenbosch that had been limed to pH 5.75 (1M KCl). Ruggeri 140 promoted the highest cane mass (vigour), highest petiole and must nitrogen (N), lowest ratio of yield to cane mass, and lowest overall wine quality. The lowest cane mass and highest wine quality were produced by vines on 110R. Petiole N, phosphorus (P), calcium (Ca) and magnesium (Mg), and must N and Ca, were also lower for vines on 110R than for those on 140Ru.

No abstract