Influence of fertiliser treatment on apple fruit composition and physiology

Abstract The contents of total phosphorus, ethanol‐soluble phosphorus, ethanol‐insoluble phosphorus, magnesium, calcium, and potassium were determined in tissue of apple fruits from trees receiving no fertiliser (U) and from trees receiving the fertiliser treatments N, P, NP, and NPK (N=21b sulphate of ammonia, P=4 lb superphosphate, and K=l lb sulphate of potash per tree per year). In comparison with tissue from U fruit, tissue from P fruit possessed higher total, ethanol‐soluble, and ethanol‐insoluble phosphorus contents and a slightly lower potassium content. Treatment N resulted in increased levels of calcium and potassium but a markedly reduced phosphorus content. Calcium, magnesium, and phosphorus levels were elevated as a result of treatments NP and NPK; the latter treatment also resulted in a higher potassium content. Incidence of internal breakdown was negatively correlated with total and ethanol‐soluble phosphorus contents, but not with the contents of magnesium, calcium, or potassium.