Reaction of EDTA, DTPA, and EDDHA Complexes of Zinc, Copper, and Manganese with a Calcareous Soil

When Zn is added to calcareous soils to avoid Zn deficiencies, it can be fixed, if the source is a soluble inorganic salt, and leached, if it is a stable complex. Relative mobilities of Zn−EDTA and Zn−lignosulfonate (LS) chelates added to calcareous soil columns as coated and uncoated fertilizers were determined. Zn−EDTA migrated and distributed throughout the columns. About 51% of the Zn was leached with uncoated fertilizers but only about 10% when coated fertilizers were used. Zn−LS migrated very little, especially with coated fertilizers; the Zn remained mostly in the upper zone of the column and was not leached. The distribution of the added Zn between different fractions of soil was determined by a sequential extraction procedure. When Zn−EDTA was added, the percentage of the most labile fractions increased slightly with respect to the control soil throughout the entire profile of the column. Zn−LS displayed higher increases in the most labile fractions but only in the top layer of the column. Correlations between the extracted fractions (P < 0.001%) showed that in general a dynamic equilibrium existed between them. DTPA-extractable Zn correlated (P < 0.001%) with the two most labile fractions and to a lesser extent with the nonbioavailable forms. Comparisons between coated and uncoated fertilizers show that the presence of coatings benefits Zn−EDTA fertilizers, decreasing the leaching and increasing the amount of biavailable Zn, but had no beneficial effect for Zn−LS fertilizers. Keywords: Zn chelates; controlled-release; calcareous soil columns; speciation; leaching

Section: Resultsmentioning

confidence: 99%

Lixiviation and Extraction of Zinc in a Calcareous Soil Treated with Zinc-Chelated Fertilizers

Álvarez

Rico

Obrador

1996

“…This steric interaction between the methyl groups does not occur in rac-Fe-EDDHA but may reduce the stability of rac-Fe-EDDHMA with respect to meso-Fe-EDDHMA. Adsorption or "fixation" of chelating agents in soils was recognized in early investigations of the agricultural uses of synthetic chelating agents (4)(5)(6)(7)(8)(9)(10)(11)(12). The effectiveness of Fe chelates as Fe sources and carriers in soil can be severely limited by the adsorption of Fe chelates or chelating agents in the solid phase (13).…”

Section: Introductionmentioning

confidence: 99%

Fe(III)−EDDHA and −EDDHMA Sorption on Ca-Montmorillonite, Ferrihydrite, and Peat

Hernández‐Apaolaza

Lucena

2001

The effectiveness of Fe chelates as Fe sources and carriers in soil can be severely limited by the adsorption of Fe chelates or chelating agents in the solid phase. To study this phenomenon, well-characterized peat, Ca-montmorillonite, and ferrihydrite were used as model compounds, and the adsorption of Fe-EDDHA and Fe-EDDHMA chelates were studied. Sorption isotherms for the meso and racemic isomers of these chelates on the soil materials are described. The variability of sorption with pH in peat and ferrihydrite was also determined because both have variable surface charge at different pH values. In montmorillonite, at low concentrations, the retention of Fe from the Fe-EDDHMA chelate is greater than the one of the Fe-EDDHA chelate. As well as the concentration increased, the inverse situation occurs. The behavior of both meso and racemic isomers of chelates in contact with Ca-montmorillonite is similar. The Fe-meso-EDDHA isomer was highly adsorbed on ferrihydrite, but the racemic isomer is not significantly retained by this oxide. For Fe-EDDHMA isomers, the racemic isomer was more retained by the oxide, but a small sorption of the racemic isomer was also observed. Results suggest that Fe-EDDHA chelates were more retained in peat than Fe-EDDHMA chelates. The most retained isomer of Fe-EDDHA was the meso isomer. For Fe-EDDHMA, the adsorption was very low for both racemic and meso isomers.

“…The highest Zn concentration in the most labile fraction (WSEX) occurred with the Zn-EDTA treatments, and Zn concentrations with both rates of Zn-EDDHA fertilizer were approximately three times lower, although Zn-EDTA and Zn-EDDHA complexes in aqueous solutions have similar pK values (pK Zn-EDTA ) -17.4 and pK Zn-EDDHA ) -17.8 with ionic strength of 0.01 M; 42). Aboulroos (43) reported that the Zn-EDDHA molecule was unstable in a calcareous soil and that adsorption of the Zn-EDDHA molecule by soil was the main process of removing Zn from solution. The influence of time on Zn associated with this fraction (WSEX) can be observed in Figure 2 for Zn-EDTA and Zn-EDDHA fertilizers.…”

Section: Resultsmentioning

confidence: 99%

Effects of Zinc Complexes on the Distribution of Zinc in Calcareous Soil and Zinc Uptake by Maize

Álvarez

Beltrán

2003

The movement and availability of Zn from six organic Zn sources in a Typic Xerorthent (calcareous) soil were compared by incubation, column assay, and in a greenhouse study with maize (Zea mays L.). Zinc soil behavior was studied by sequential, diethylenetriaminepentaacetate, and Mehlich-3 extractions. In the incubation experiment, the differences in Zn concentration observed in the water soluble plus exchangeable fraction strongly correlated with Zn uptake by plants in the greenhouse experiment. Zinc applied to the surface of soil columns scarcely moved into deeper layers except for Zn-ethylenediaminetetraacetate (EDTA) that showed the greatest distribution of labile Zn throughout the soil and the highest proportion of leaching of the applied Zn. In the upper part of the column, changes in the chemical forms of all treatments occurred and an increase in organically complexed and amorphous Fe oxide-bound fractions was detected. However, the water soluble plus exchangeable fraction was not detected. The same results were obtained at the end of the greenhouse experiment. Significant increases were found in plant dry matter yield and Zn concentration as compared with the control treatment without Zn addition. Increasing Zn rate in the soil increased dry matter yield in all cases but Zn concentration in the plant increased only with Zn-EDTA and Zn-ethylenediaminedi-o-hydroxyphenyl-acetate (EDDHA) fertilizers. Higher Zn concentration in plants (50.9 mg kg(-)(1)) occurred when 20 mg Zn kg(-)(1) was added to the soil as Zn-EDTA. The relative effectiveness of the different Zn carriers in increasing Zn uptake was in the order: Zn-EDTA > Zn-EDDHA > Zn-heptagluconate >/= Zn-phenolate approximately Zn-polyflavonoid approximately Zn-lignosulfonate.