Comparison and modelling of extraction methods to assess agronomic effectiveness of fertilizer zinc

Total Zn in fertilizer is a poor predictor of Zn availability in granular fertilizers. In this study, we compared different extraction methods using Zn fertilizers for which the agronomic effectiveness had previously been determined. Sixteen fertilizers were extracted by eight different procedures u...

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Bibliographic Details
Published in:Journal of plant nutrition and soil science 2020-04, Vol.183 (2), p.248-259
Main Authors: Degryse, Fien, da Silva, Rodrigo C., Baird, Roslyn, Cakmak, Ismail, Yazici, Mustafa Atilla, McLaughlin, Mike J.
Format: Article
Language:English
Subjects:
Acetic acid
agronomic effectiveness
Agronomy
Ammonium
Ammonium acetate
Availability
Chelation
Chemical speciation
Correlation
Equilibrium methods
Ethylenediaminetetraacetic acids
Extractants
extraction methods
fertilizer
Fertilizers
Modelling
pH effects
Solubility
Speciation
Visual observation
Zinc
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Summary:Total Zn in fertilizer is a poor predictor of Zn availability in granular fertilizers. In this study, we compared different extraction methods using Zn fertilizers for which the agronomic effectiveness had previously been determined. Sixteen fertilizers were extracted by eight different procedures using five extractant solutions: water, 1 M ammonium acetate (pH 7.0), 74 mM EDTA (pH 7.0), 5 mM DTPA + 0.1 M MES (pH 6.2), and 0.12 M bis‐tris (pH 6). Modelling of Zn solubility and speciation was carried out with a chemical speciation program (Visual Minteq). The predicted solubilities were in good agreement with the observations, indicating chemical equilibrium. The three methods using pure water were highly correlated with each other and showed the strongest correlation with agronomic effectiveness (r = 0.81–0.90). The methods using extractants with strong pH buffering or high chelating capacity showed no or weak correlation with the agronomic effectiveness. Thus, water‐only based methods give the best indication of the availability of Zn in granular fertilizers, and are best suited for regulation or labeling of available Zn in fertilizer.
ISSN:1436-8730
1522-2624
DOI:10.1002/jpln.201900340