The use of iron chelates in compound fertilizers containing trace elements
Titel:
The use of iron chelates in compound fertilizers containing trace elements
Auteur:
Boxma, R. van Luit, B.
Verschenen in:
Communications in soil science and plant analysis
Paginering:
Jaargang 14 (1983) nr. 4 pagina's 321-333
Jaar:
1983-06
Inhoud:
The chemical behaviour of iron chelates, incorporated in compound fertilizers with inorganic micronutrient compounds, was studied. Pot experiments were conducted to evaluate the effectiveness of these products in controlling iron deficiency. A commercial compound fertilizer, containing 0.09% Fe as Fe-DTPA, 0.12% Cu, 0.16% Mn and 0.04% Zn as sulfates, proved to be ineffective in preventing iron chlorosis in Chamaecyparis lawsoniana 'Alumii', growing on sphagnum peat at two lime levels. The same fertilizer formulation with 0.09%- Fe as Fe-EDDHA did prevent iron chlorosis at both lime levels. Fe-EDTA, incorporated in the compound fertilizer, gave good results at the lower but not at the higher lime level, due to the low stability of Fe-EDTA at high pH. Data from laboratory experiments showed that copper replaced the chelated iron in the compound fertilizer containing Fe-DTPA, causing the iron to precipitate. The strong competition between copper and iron for the organic ligand is due to a specific affinity of copper for DTPA, resulting in a copper chelate with high stability constant and a molar ratio of copper to chelating agent of 2 : 1. In the case of Fe-EDDHA and Fe-EDTA the competition between iron and copper is much weaker. In contrast to Fe-DTPA, these chelates remain rather stable when incorporated in fertilizers containing micronutrients.
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