Efficacy of HBED/Fe3+ at supplying iron to Prunus persica in calcareous soils

To date, the application of synthetic Fe chelates has been the most effective solution to correct Fe chlorosis. Commercial products based on the EDDHA/Fe3+ (ferric ethylenediamine-N,N'-bis(hydroxyphenylacetate)) are the most effective and commonly used; however, their synthesis produces products with a low purity (similar to 6% chelated Fe). The aims of this work were to study the effectiveness of 2 Fe chelates of higher purity, HJB (N,N'-bis(2-hydroxy-5-methylbenzyl)ethylenediamine-N,N'-diacetic acid) and HBED (N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid), to prevent and correct the Fe deficiency in nectarine and flat peach trees, respectively, grown in alkaline field conditions and to compare their effectiveness with the traditional EDDHA. Tree status was evaluated during 2 growing seasons, and nutritional parameters related to the Fe concentration in leaves and flowers, the SPAD index and micronutrient ratios were evaluated. Moreover, the yield and the size of fruit were evaluated in the experiment with nectarine trees. Parameters such as the SPAD index, the Fe concentration and the Fe/Mn ratio in leaves showed that EDDHA/Fe3+, HJB/Fe3+ and HBED/Fe3+, especially at low doses, presented a similar ability to prevent chlorosis symptoms in nectarine trees. Chlorotic flat peach trees treated with commercial EDDHA/Fe3+ showed a faster regreening (SPAD index) during the first year of chelate application; however, no significant differences among treated trees could be observed at the end of the second growing season. The results of measuring Fe concentration in leaves were not as conclusive; however, flower analysis after the treatment application showed a good recovery in treated trees. These studies show the efficacy of chelates with a purer composition than the traditional EDDHA/Fe3+ to correct and prevent Fe deficiency. (c) 2012 Elsevier B.V. All rights reserved.