During two successive years 2001 and 2002 Thompson Seedless grapevines
were subjected to summer pruning practices (head suckering + pinching the main
shoots and topping the laterals) and mineral nutrition of chelated Fe, Zn and Mn
together at 0.1 % each, applied after head suckering; 10 days before anthesis and after fruit set (at 3mm berry diameter). The vines received one, two or three sprays of
Fe + Zn + Mn according to the time of spraying. The number of treatments was ten.
Shoot growth rate was in April> in May> in June> in July. All treatments increased
shoot growth rate compared with the control. Carbohydrate content of the cane was
higher in February then decreased in March and April. The content remained almost
unchanged from April to August. Carbohydrate content of the shoot increased
progressively. Spraying Fe, Zn and Mn + summer pruning increased carbohydrate
content in canes; shoots and new canes, especially when applied 10 days before
anthesis. Bunch weight, yield, TSS, Fe. Zn and Mn were increased, whereas acidity
was decreased. The number of clusters/vine was not affected in the year of
application. However, it was significantly increased in the following season. The
results indicated that one spray of Fe + Zn + Mn at 0.1 % each 10 days before
anthpc:k; .,. summer pruning seemed to be sufficient and reduced mineral nutrition
costs by about 50% at least.