Dynamics of calcium uptake with pre-harvest sprays to reduce bitter pit in 'Golden Delicious'
The experiment was conducted as part of a more comprehensive study on bitter pit under South African conditions. Mature, bearing 'Golden Delicious' trees on a commercial farm were selected for the trial. Fruitlets were sampled weekly before a calcium (Ca) application was made and mineral analyses performed from 40 dafb (days after full bloom) until harvest. The accumulation pattern of Ca in the fruit was followed through the season and compared to a similar study in Italy. The increase in total Ca content of the fruit at harvest, due to external Ca applications, confirmed existing results. The most dramatic increase occurred from approximately 100 dafb. However, the seasonal accumulation pattern of the Ca differed through the season and results suggested a twofold increase, starting at 40 dafb, with short delay around 80 dafb, and continued to increase until harvest. The short suspension in Ca accumulation probably corresponded with the completion of cell division and final stages of shoot growth. The application of pre-harvest foliar Ca reduced the incidence of bitter pit in comparison to the control which received no foliar Ca applications during that season.