THE INFLUENCE OF MINIMAL NPK FERTILISATION ON THE QUANTITY AND QUALITY OF APPLE YIELDS

During an annual cycle, fruit trees go through developmental stages, characterised by a higher demand for some mineral elements, called critical periods, which coincide with the phenophases of bud opening and shoot initiation. Research on mineral nutrition in fruit growing has highlighted that the maximum consumption of nutrients is during the period of shoot growth, fruit development and differentiation of fruit buds. In apple, flowering is influenced more by the time of fertiliser application and the form of nitrogen than by the amount applied, as apple has high requirements for the element phosphorus in the phenophases of intense shoot growth and wood maturation. Fertilisation with NPK increased apple yield for both fertilisation treatments compared to the unfertilised control treatments. After applying 270 kg·ha⁻¹ NPK in the first year of the experiment, very significant production increases were obtained, 4.46t·ha⁻¹, with a content of 16% dry matter, 13.13°Brix soluble matter and a titratable acidity of 0.465 mg malic acid/100 g.