Foliar fertilization with potassium, magnessium and calcium and postharvest fruit quality in plums (prunus domestica l)

Proceedings of the International Conference “Environmentally friendly and safe technologies for quality of fruit and vegetables”, held in Universidade do Algarve, Faro, Portugal, on January 14-16, 2009. This Conference was a join activity with COST Action 924.Foliar applications of fertilizers are an important part of standard fertilization programmes in apples to optimize the content of nutrients important to growth and fruit quality. In an experiment in plums (Prunus domestia L.) a foliar fertilization programme was compared to traditional application of fertilizers on the soil. In another experiment extra magnesium, potassium and the combination of both magnesium and potassium were compared to control trees given a standard foliar fertilization programme. Yield and fruit size was registered. Analyses included fruit quality factors, content of major nutrients in fruits and leaves as well as storability. The effects of the different programmes on yield, fruit size and most fruit quality factors were not significant. Fruits from trees given foliar fertilizers had, however, higher content of nitrogen and significantly lower contents of the other major nutrients. The application of extra potassium and magnesium did not increase the level of these elements, but a significant reduction in the Ca-content was observed. Accordingly a higher K:Ca-ratio was observed in potassium and magnesium sprayed fruits. Even though no differences in fruit firmness were observed between the treatments at harvest, after two weeks of storage the plums from potassium sprayed trees were significantly softer than the controls