Effects of soil and foliar treatments of alone and combined applications of boron with iron and zinc on boron, zinc, and iron contents of Gemlik olive trees

Abstract

This study was conducted to evaluate the effectiveness of various treatments in correction of alone boron (B) and multiple B, zinc (Zn), and iron (Fe) deficiencies in olive table cultivar (Gemlik) in the southeastern Marmara region of Turkey. This work consisted of four field experiments which mainly included control, soil, and foliar applications of B alone and combinations with Zn and Fe. In experiment I, borax was applied alone foliarly and via soil. In the other three experiments, double and triple combinations of iron(II) sulfate heptahydrate (FeSO4 center dot 7H(2)O) and zinc sulfate heptahydrate (ZnSO4 center dot 7H(2)O) with borax were applied foliarly and via soil. Soil applications of the compounds were only performed in the first year of the experiments. However, the leaves and the fruits were sampled in the following year to estimate the residual effect of soil applications. Foliar applications were sprayed onto leaves twice and four times at two doses in consecutive years. Soil and foliar applications of borax increased leaf and fruit B concentrations. However, foliarly treated B was more effective than soil application. Four times foliar applications of boron in each season seemed to be appropriate treatment to maintain a sufficient B level in olive trees. Foliar applications of double and triple combinations of FeSO4 center dot 7H(2)O and ZnSO(4 center dot)7H(2)O with borax increased significantly Fe and Zn concentrations in the leaves as well. Boron concentrations were dramatically higher in the fruits than in the leaves. These results clearly indicated the translocation of B from soil and treated leaves to the fruits. Therefore, fruit B concentration was more descriptive in the evaluation of the B nutrition level of olive trees.