ABSTRACT
Pre-harvest foliar applications to increase fruit calcium (Ca) content and reduce bitter pit incidence, is a standard practice world wide. We re-evaluated the effectiveness of early season applications versus late applications of calcium nitrate (Ca(NO3)2) to reduce bitter pit in ‘Golden Delicious,’ under the present environmental conditions of the Western Cape, South Africa. Two periods of efficient uptake of external Ca were identified, viz., during cell division and the last few weeks before harvest. Foliar Ca applications during mid season (from 40 d after full bloom) were more effective in increasing fruit Ca content and reducing bitter pit incidence, than later applications. Thus, it is important to apply the bulk of the Ca(NO3)2 during the first few weeks after cell division to maximize the Ca content of ‘Golden Delicious’ apples.
Notes
∗ Phase I is approx. 40 to 74 dafb; Phase II is approx. 84 to 120 dafb.
∗∗ Recommended dosage for Ca(NO3)2 foliar application per 100 L water.
∗Logit% bitter pit = LOG ((Bitter pit fruit +0.5)/(Total no. of fruit −bitter pit fruit +0.5)).
∗Logit% bitter pit = LOG ((Bitter pit fruit +0.5)/ (Total no. of fruit −bitter pit fruit +0.5)).
∗Phase I is approx. 40 to 74 dafb; phase II is approx. 84 to 120 dafb.