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Effects of pre-harvest calcium nitrate and calicium chloride sprays on apple.

Wooldridge, J.; Joubert, M. E.; Lourens, F. C.;

Deciduous Fruit Grower Year: 1998 Vol: 48 Issue: 5 Pages: 1-6 Ref: 8 ref.

1998

บทคัดย่อ

Effects of pre-harvest calcium nitrate and calicium chloride sprays on apple.

During 1994-95, spray trials were conducted in 12-year-old Golden Delicious, Granny Smith and Topred orchards in Grabouw, South Africa. Ca was applied as: (1) commercial crystalline CaCl2 containing approx equal to 27% Ca (CCC) at 500 g CCC/100 litres; (2) a locally manufactured liquid CaCl2 formulation containing 11.6% Ca (LCC) at 250, 500 or 750 ml LCC/100 litres; or (3) a 50% calcium nitrate solution containing 12% Ca (LCN) at 650 ml LCN/100 litres. Sprays were applied until runoff to the entire tree surface at 10-day intervals between the first week of December and the last week in January. All 3 apple cultivars were scorched by the CCC treatments. In the LCC treatments, scorch severity increased with increasing LCC concentration. Granny Smith was the only cultivar to be significantly scorched by applications of 250 ml LCC/100 litres (0.25% LCC). In Golden delicious and Topred, the incidences of bitter pit and rot after storage were reduced by all spray regimes. Therefore, it is suggested th

at these disorders can be controlled in these cultivars by applications of 0.25% LCC. In Granny Smith, 0.25% LCC was not sufficient for control of bitter pit, although all the other treatments reduced the disorder by approx equal to 50% compared with controls. All 5 sprays increased russet in Golden Delicious, and had no effect on russet in Topred. In Topred all sprays resulted in increased fruit quality, whereas in Granny Smith, only 0.75% LCC increased export quality. In Golden Delicious, beneficial effects of Ca treatments were offset by increased russeting. Fruit colour and mass were not affected by the treatments. Leaf Ca levels under the different treatments are discussed. The Ca sprays tended to result in reduced foliar Mn, Cu and Zn in all 3 cultivars, and reduced K in Topred. The sprays did not affect fruit K. Sprays of CCC and LCC reduced fruit Mg in Granny Smith.