THE EFFECT OF K-FERTILIZATION ON APPLE FRUIT CA CONCENTRATION AND QUALITY
An assessment of the effects of K-fertilization on Ca nutrition and quality of fruit was possible in several randomized, replicated field experiments undertaken in the past decade.
At a K-deficient site, annual fertigation of 15 g K tree-1 as KCl prevented the development of K-deficiency for the first five growing seasons in a high-density apple orchard of Gala, Fuji Fiesta and Spartan cultivars on M.9 rootstock.
Potassium fertigation increased leaf and fruit K concentration, size, titratable acidity and red coloration of fruit at harvest for all cultivars.
Measured decreases in fruit Ca concentration were associated with increased fruit size rather than differences in absolute Ca uptake per fruit.
At a different site, seven annual K-fertigation treatments testing chloride, sulphate, thiosulphate and magnesium sulphate forms of K were applied for three years to Jonagold on M.9 rootstock.
All fertigated K forms increased leaf and fruit K concentrations, but did not affect fruit quality or size, which was large.
Fruit Ca concentration was low and incidence of bitter pit high, but neither was adversely affected by form of fertigated K. In a third experiment, 0, 100 or 200 kg K ha-1 year-1 as potassium-magnesium sulphate (KMag) were surface applied for three years in ten grower orchards planted to Fuji/M.9 or 0.3 rootstock.
KMag applications consistently increased extractable soil Mg and K concentrations within the root zone by third year.
This usually increased leaf and fruit K concentration and occasionally decreased leaf Mg and fruit Ca concentration.
Incidence of bitter pit was unaffected by treatments.
Neilsen, G.H. and Neilsen, D. (2006). THE EFFECT OF K-FERTILIZATION ON APPLE FRUIT CA CONCENTRATION AND QUALITY. Acta Hortic. 721, 177-184
DOI: 10.17660/ActaHortic.2006.721.23
https://doi.org/10.17660/ActaHortic.2006.721.23
DOI: 10.17660/ActaHortic.2006.721.23
https://doi.org/10.17660/ActaHortic.2006.721.23
Malus domestica Borkh., potassium, calcium, magnesium, fruit quality
English