Long-term bioavailability effects of synthesized zinc chelates fertilizers on the yield and quality of a flax (Linum usitatissimum L.) crop

Abstract

The aim of this study was to compare the residual effects in soil and the influence on a flax crop (Linum usitatissimum L.) of applying Zn from different commercial synthetic chelates. The chelates used were: Zn-EDDHSA (Zn-ethylenediamine-N,N'-bis(2-hydroxyphenylacetate), Zn-EDTA (Zn-ethylenediaminetetraacetate), Zn-HEDTA (Zn-N-2-hydroxyethyl-ethylenediaminetriacetate), Zn-EDTA-HEDTA and Zn-DTPA-HEDTA-EDTA (Zn-DTPA, Zn-diethylenetriaminepentaacetate). The experiment was conducted in a greenhouse using two different soils (Soilacid: a weakly acidic soil and Soilcalc: a calcareous soil). Each treatment was administered, in a single application, to a previous flax crop at different Zn application rates. The yield and some of the flax crop quality parameters were determined in the present flax crop. Soil Zn behavior was then evaluated by single and sequential extraction. In Soilacid, the Zn-HEDTA and Zn-EDDHSA fertilizers produced the highest plant parameters values (total Zn concentration, total uptake Zn), percentages of Zn utilization and values of the transfer factor, TF. In contrast, in Soilcalc these fertilizers produced the lowest in-plant values, with this soil producing the highest yield, quality, percentage of utilization and TF associated with the application of Zn-DTPA-HEDTA-EDTA and Zn-EDTA fertilizers. However, the Zn-EDTA in Soilacid and Zn-DTPA-HEDTA-EDTA in Soilcalc, were associated with the greatest amounts of bioavailable Zn in soil and also with the highest Zn concentrations associated with the sum of the most labile fractions (water soluble plus exchangeable fractions). The residual Zn produced by the different fertilizer treatments estimated using the DTPA, Mehlich-3- and LMWOAs methods- was available in sufficient quantities that it not be necessary to add any further Zn (which could have resulted in over-fertilization) for the subsequent crop to either of the soils.