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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED HORTICULTURAL PRODUCTION SYSTEMS FOR WATER QUALITY PROTECTION AND WATER CONSERVATION Title: Extraction of Micronutrient Metals from Peat-based Media Using Various Chelate-ligand and Iron-source Extractants

Author
item Albano, Joseph

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 2011
Publication Date: N/A

Interpretive Summary: The binding preference of a chelate for a metal is based on the stability of the complexation and the pH in which the reaction occurs. In the present study, two experiments were conducted to assess chelate binding preference for Cu, Fe, Mn, and Zn in a commercially-available peat-based medium. In experiment 1 chelate-ligand extractant solution were studied and found that pH ranged from 9.7 (EDDS) to 2.3 (DTPA), and extract solution pH ranged from 7.2 (EDDS) to 4.7 (DTPA) demonstrating the buffering capacity of the peat-based medium. Extractant solutions of EDDS and DTPA resulted in the lowest and highest levels of Cu (0.06 - 0.14 ppm)and Fe (4.3 -13.1 ppm) in extract solutions. In experiment 2, iron-source extractant solution pH ranged from 7.1 (FeEDDS) to 5.4 (FeSO4). The extract pH for all Fe-source treatments was similar at pH 6.7. Iron recovery rates in extracts for the Fe-chelate treatments exceeded 100% at 1.9 ppm Fe, FeDTPA; 1.7 ppm Fe , FeEDTA; 1.5 ppm Fe, FeEDDS; 1.4 ppm Fe, FeEDDHA; with FeSO4 and DI water control treatments having Fe recovery rates less than 100% at 0.9 and 0.7 ppm Fe, respectively. Among Fe-source treatments, Mn was not different, averaging 0.03 ppm, and Cu and Zn was greatest in the FeEDDS treatment at 0.04 and 0.24 ppm, respectively.

Technical Abstract: Objectives of the study were to determine effects of chelate-ligand (experiment 1) and iron-source (experiment 2) unbuffrered extractant solutions on substrate pH and Cu, Fe, Mn, and Zn extraction from peat-based media. Chelate-ligand extractants consisted of 5 mM solutions of ethylenediaminedisuccinic acid (EDDS), ethylenediaminetetraaceitc acid (EDTA), and diethylenetriaminepentaacetic acid (DTPA). Iron-source extractants consisted of 1 ppm Fe solutions derived from FeEDDS, FeEDTA, FeDTPA, Fe-ethylenediamine-N,N'-bis(2-hydroxyphenylacetic) acid (FeEDDHA), and FeSO4. Extractions were performed using the 1:2 substrate analysis method with a incubation period of 24-hours. The control was distilled-dionized water extractions. Chelate-ligand extractant solution pH ranged from 9.7 (EDDS) to 2.3 (DTPA), and extract solution pH ranged from 7.2 (EDDS) to 4.7 (DTPA) demonstrating the buffering capacity of the peat-based medium. Extractant solutions of EDDS and DTPA resulted in the lowest and highest levels of Cu (0.06 - 0.14 ppm)and Fe (4.3 -13.1 ppm) in extract solutions. Iron-source extractant solution pH ranged from 7.1 (FeEDDS) to 5.4 (FeSO4). The extract pH for all Fe-source treatments was similar at pH 6.7. Iron recovery rates in extracts for the Fe-chelate treatments exceeded 100% at 1.9 ppm Fe, FeDTPA; 1.7 ppm Fe , FeEDTA; 1.5 ppm Fe, FeEDDS; 1.4 ppm Fe, FeEDDHA; with FeSO4 and DI water control treatments having Fe recovery rates less than 100% at 0.9 and 0.7 ppm Fe, respectively. Among Fe-source treatments, Mn was not different, averaging 0.03 ppm, and Cu and Zn was greatest in the FeEDDS treatment at 0.04 and 0.24 ppm, respectively.

Last Modified: 8/29/2014
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