Effect of ferric chloride additions on the solubility of ferric ion in a near‐neutral soil

Abstract

The concentration of ferric ion and the ion product of ferric hydroxide in the Weld loam (Aridic Paleustoll) were estimated from equilibria of EDTA (ethylenediaminetetraacetic acid) chelates. Additions of ferric chloride to the Weld loam raised the solubility of soil iron at least seven‐fold. The (Fe³⁺)(OH^‐)³ ion product increased from approximately 10^‐39.2 to at least 10^‐38.4 after ferric chloride was added. The solubility of soil iron decreased slowly with time after fertilization. After one month the (Fe³⁺)(OH^‐)³ ion product had fallen to 10‐^39.1, virtually the same level as in the unamended soil. The results are consistent with the hypothesis that iron oxides of high specific surface or poor crystalinity control the solubility of ferric ion in soil solution.

1.

This paper was presented, edited, and accepted as part of the International Symposium on Iron Nutrition and Interactions in Plants, which was published in the Journal of Plant Nutrition 5 (4 to 7), 1982. Due to error in editorial handling, this paper was inadvertently omitted from the published symposium. The editors regret the inconvenience to all concerned. S.D. Nelson, A. Wallace, J.C. Brown, G.W. Miller, W.L. Lindsay, and V.D. Jolley.

2.

Colorado State University Experiment Station Scientific Series Paper No. 2755.

Key words:

• EDTA
• Chelate
• Iron oxide
• Ferrihydrite

Notes

This paper was presented, edited, and accepted as part of the International Symposium on Iron Nutrition and Interactions in Plants, which was published in the Journal of Plant Nutrition 5 (4 to 7), 1982. Due to error in editorial handling, this paper was inadvertently omitted from the published symposium. The editors regret the inconvenience to all concerned. S.D. Nelson, A. Wallace, J.C. Brown, G.W. Miller, W.L. Lindsay, and V.D. Jolley.

Colorado State University Experiment Station Scientific Series Paper No. 2755.