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Effect of Phosphorus and Zinc Fertilization on the Solubility of Zn 2+ in Two Alkaline Soils
Author(s) -
Norvell W. A.,
DabkowskaNaskret H.,
Cary E. E.
Publication year - 1987
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1987.03615995005100030006x
Subject(s) - chemistry , ethylenediaminetetraacetic acid , soil water , zinc , phosphorus , calcareous , divalent , solubility , chelation , calcareous soils , alkali soil , fertilizer , inorganic chemistry , environmental chemistry , nuclear chemistry , geology , paleontology , organic chemistry , soil science
Concentrations of Zn 2+ in equilibrium with two alkaline soils were calculated from the reactions of EDTA (ethylenediaminetetraacetic acid) chelates. The initial speciation of EDTA was varied to allow equilibrium with Zn 2+ concentrations in the soil to be approached from above and below. Fertilizer Zn was added at 0 to 5 mg kg −1 as ZnSO 4 and reacted thoroughly with the soil before additions of P or EDTA chelates. Phosphorus was added at 0 or 62 mg kg −1 as a mixture of KH 2 PO 4 and K 2 HPO 4 . Concentrations of soluble Zn 2+ in unfertilized soil were extremely low, approximately 5 × 10 −10 M in the noncalcareous soil at pH 7.2 and 1 × 10 −10 M in the calcareous soil at pH 7.6. These Zn 2+ concentrations were raised 7‐ to 14‐fold by 5 mg kg −1 of added Zn, and the higher levels persisted for at least 11 weeks. Buffering of Zn 2+ by the soils was substantial, ranging from about 15 to 45 (nmol g −1 )/(nmol L −1 ). Additions of P caused small decreases in the concentrations of Zn 2+ and other divalent cations in solution. Only in the Zn‐fertilized calcareous soil were the percent decreases in Zn 2+ greater than those of the major divalent cations, Ca 2+ and Mg 2+ . This effect of P in the calcareous soil is of special interest because of its apparent selectivity for Zn, but the effect was small as shown by reductions of only 12 to 19% in the [Zn 2+ ]/[Ca 2+ + Mg 2+ ] concentration ratio.