Lower nitrogen nutrition determines higher phenolic content of organic apples Juozas Lanauskas1, Darius Kviklys1, Mindaugas Liaudanskas2, Valdimaras

Abstract

Phenolic content of apples from an integrated and organic apple tree orchard was analysed at the Institute of Horticulture of Lithuanian Research Centre for Agriculture and Forestry in 2012–2013. Apples of ‘Lodel’ and ‘Aldas’ cultivars on rootstock B.396 in 8–9<sup>th</sup> leaf were tested. Nitrogen and potassium fertilizers were applied annually at the rates of 50 kg/ha N and 66.4 kg/ha K in an integrated fruit orchard. A mixture of perennial grasses with 25% of white clover was sown in interrows in the second year after tree establishment in the organic production system. Every two years sward in alternate interrows was tilled for natural organic matter mineralization. Fertilizers were not used in the organic apple orchard. Organic apples of both cultivars had a higher content of procyanidins B1 and B2, phloridzin, chlorogenic acid, (+)-catechin, and (–)-epicatechin. Organic ‘Aldas’ apples also contained more hyperoside, avicularin and quercitrin than non-organic apples. On average, the total phenolic content of organic apples of both cultivars was 43% higher than that of apples from the integrated orchard. These differences could be explained by nitrogen nutrition: the N content in organically grown apple leaves was significantly lower than that in leaves from the integrated production system. Tree trunk diameter and yield of organic apple were less, and fruits were better coloured.