Potassium impact on apple colour

2015–2016 | Petar Bursac, Fruit Growers Victoria | Future Orchards® trial

This Goulburn Valley trial was designed to demonstrate whether potassium could improve red apple colour. The trial outline notes that red colour depends on the formation and accumulation of anthocyanin pigments and that potassium has been associated with anthocyanin development.

The work compared foliar fertiliser treatments, together with potassium supplied through irrigation, against an untreated control. The protocol also recognised that potassium is not the only nutrient associated with colour development: copper, phosphates and calcium were noted as playing roles in activation of phenylalanine-ammonia-lyase, an enzyme involved in anthocyanin biosynthesis.

The trial was established in November 2015 with colour assessment planned around harvest in 2016. Its practical value lies in testing a commonly discussed nutrition-colour relationship under commercial orchard conditions. Growers should interpret colour responses alongside crop load, light exposure, cultivar, maturity and existing soil and leaf nutrient status rather than treating potassium as a stand-alone colour solution.