Abstract

Organic citrus production has been increasing recently in Turkey. In this study, we compared several nutri-elements concentrations of organically (ORG) and conventionally (CON) grown citrus orchards in the Mediterranean region of Turkey. The samples included Satsuma mandarins (Citrus unshiu L.) and Washington navel and Valencia oranges (Citrus sinensis (L.) Osbeck), which were grafted on sour orange (Citrus aurantium L.). In 1996, 58 citrus orchards were sampled and 48 of them used for analyses. Three years after the first sampling, some orchards switched from CON to ORG production. Sampling was repeated in 2007 and included 31 samples from CON and 30 samples from orchards that switched to ORG after the 1996 samples were taken. Concentrations of N, P, K, Ca, Mg, Na, B, Cu, Fe, Mn and Zn were determined using the samples from 1996; with the exception of B, no significant differences were observed. Analysis of the samples from 2007 indicated statistically significant differences between the two groups for concentrations of N, K, Mg, B and Mn. The means of both samples were subjected to principle component analysis (PCA); the results indicated that, after several years of ORG culture, the two groups were clearly separated. The variables highly correlated with PC1 were Na, Fe and Ca, while P, K, Mn and Mg were correlated by PC2. B, Fe and Zn correlated by PC3. Several trace elements (Pb, Cu, Fe, Mn, Ni and Zn) from five randomly chosen soil samples from both CON and ORG growing groups were determined, and the results indicated that the mean concentrations for the two groups were similar for most of the elements (Pb, Cu, Fe and Ni). Our results shed light on the optimization of plant nutrient programs in organic citrus production.

Key words: Citrus, conventional, mandarin, Mediterranean, nutri-elements, orange, organic.