Treecrops
Treecrop fruit have a high potassium demand, while the tree growth has a much smaller potassium requirement. Therefore potassium should be applied during the fruit growth period and rates should be adjusted according to the annual fruit load.
In stonefruit, potassium is necessary for fruit quality and size. Similarly in citrus, potassium deficiency causes fruit to be small, while an excess makes the fruit acid and delays maturity.
Potassium is important for fruit development and must be applied before the fruit cell expansion stage.
Citrus cultivars vary more in their potassium requirements than for any other element. Larger sized, higher-acid fruits such as Navel oranges, Ellendale and Wallent mandarins, grapefruit and lemons require less potassium. Seeded oranges and mandarines including Joppas, Valencias and Imperials which have a tendency towards smaller fruit size should be maintained with high potassium levels.