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Title: Influence of FeEDDS, FeEDTA, FeDTPA, FeEDDHA, and FeSO4 on Marigold Growth and Nutrition, and Substrate and Runoff Chemistry

item Albano, Joseph
item MERHAUT, DONALD - University Of California

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2011
Publication Date: 1/1/2012
Citation: Albano, J.P., Merhaut, D.J. 2012. Influence of FeEDDS, FeEDTA, FeDTPA, FeEDDHA, and FeSO4 on Marigold Growth and Nutrition, and Substrate and Runoff Chemistry. HortScience. 47(1):93-97.

Interpretive Summary: Iron is commonly supplied in soluble fertilizers as chelates, organic compunds that bind with iron (Fe) to keep it soluble in fertilizers. This study looked at three factors important in horticultural crop production related to iron chelates: plant growth and plant nutrition, nutrients in the potting substrates, and nutrients leaving the pot as runoff. Iron treatments included the non-chelated, control treatment, iron sulfate, and four chelated iron sources: FeEDTA, FeEDDS, FeDTPA, and FeEDDHA; iron chelates commonly used in fertilizers. What we learned is that iron source treatments were non-significant for foliar (i.e. leaf) iron and zinc averaging 165 and 35 ppm, respectively, but significant for foliar copper and manganese. As a mean of iron-chelate treatments, foliar Cu and Mn levels were 43% greater and 28% less, respectively, than for the iron sulfate treatment. Soluble nutrients in potting substrate was greatest for FeDTPA. For leachates (runoff), the lowest levels of copper, iron, manganese, and zinc were associated with the non-chelated control treatment, iron sulfate. Results of the study demonstrate that iron source impacts plant nutrition, substrate chemistry, and runoff of copper, iron, manganese, and zinc.

Technical Abstract: Objectives of the study were to determine effects of Fe source on plant growth, plant nutrition, substrate chemistry and runoff chemistry. Iron source (FS) treatments consisted of Fe-aminopolycarboxylic acid (APCA) complexones iron ethylenediaminetetraacetic acid (FeEDTA), iron [S, S']-ethylenediaminedisuccinic acid (FeEDDS), iron diethylenetriaminepentaacetic acid (FeDTPA), and iron ethylenediaminedi-o-hydroxyphenylacetic acid (FeEDDHA); and non-chelated iron sulfate (FeSO4) added to a base nutrient solution at the rate of 1 mg•L-1 Fe final concentration. Marigold (Tagetes erecta) 'First Lady' was grown in peat-based media fertilized with FS treatments over a period of 47 days. Iron source treatments were nonsignificant for foliar Fe, Mn, or Zn, averaging 162 µg•g-1 Fe, 228 µg•g-1 Mn, and 35 µg•g-1 Zn, but were significant for foliar Cu. Main effects of FS and pour-through (PT) substrate leachate pH were statistically different but not practically significant, averaging 6.41. The FeDTPA treatment, in general, resulted in higher levels of Cu, Fe, Mn, and Zn in PT extracts. Leachate-runoff (LR) was collected and analyzed over the course of the study. Results of LR were similar to PT with levels of Cu, Fe, Mn, and Zn for the FeDTPA treatment resulting in higher concentrations of these metals. Spectrophotometer analyses results of PT and LR leachates determined the presence Fe-chelates in those solutions.