Sources and doses of fertilizers affect foliar and fruit mineral composition of ‘Daiane’ apples

Abstract

Excess fertilizer, whether organic or mineral, can promote several nutritional disorders in apple plants, affecting the production and fruit quality. The objective of this experiment was to evaluate the effects of sources and doses of N and of supplemental K and P on foliar and fruits mineral composition of 'Daiane' apples. Eight treatments were tested for nine years including: a control, a soil application of three levels of N as ammonium nitrate (AN1, AN2 and AN3), one level of N as poultry manure, one level of AN plus K, one level AN plus P and K, and one level of N as calcium nitrate, via annual soil applications. Macro and micronutrients were determined in leaves sampled at the eighth and ninth years after planting, and Ca, K, Mg, N and P in the fruit flesh sampled at the seventh, eighth and ninth years after planting. An annual poultry manure application increased the P, K and B content in leaves and apple fruits in comparison to the control. An annual application of 60 kg ha(-1) of K(2)O and 75 kg ha(-1) of N also increased the K content in leaves and fruits. The P and K content and the (K+Mg)/Ca ratio in the fruits increased with the annual application of 75, 20 and 40 kg ha(-1) of N, K(2)O and P(2)O(5), respectively. High doses of fertilizers, whether organic or mineral, affect the foliar and fruits mineral composition of 'Daiane' apples and can compromise the fruit quality by increasing the risk of physiological disorders.