Potassium is one of the most important nutrients for a number of quality characteristics. Yet, it is important that potassium concentrations are in balance with other nutrients, particularly calcium, as preferential uptake of potassium over calcium will significantly induce to greater incidence of bitter pit. It is generally accepted that K:Ca ratio should be around 15 for fruit at 40 - 60g and no higher than 30 at harvest in order to reduce bitter pit problems.
Soil supply is important, but this should be backed by fruit applied sprays targeted to get more calcium into the apple. The greater the number of sprays the better the fruit quality and it is important to continue spraying right through to harvest.
