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Contribution of calcium oxalate to soil-exchangeable calcium

Soil Science

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DOI: 10.1097/SS.0000000000000029

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Abstract

Acid deposition and repeated biomass harvest have decreased soil calcium (Ca) availability in many temperate forests worldwide, yet existing methods for assessing available soil Ca do not fully characterize soil Ca forms. To account for discrepancies in ecosystem Ca budgets, it has been hypothesized that the highly insoluble biomineral Ca oxalate might represent an additional soil Ca pool that is not detected in standard measures of soil-exchangeable Ca. We asked whether several standard method extractants for soil-exchangeable Ca could also access Ca held in Ca oxalate crystals using spike recovery tests in both pure solutions and soil extractions. In solutions of the extractants ammonium chloride, ammonium acetate, and barium chloride, we observed 2% to 104% dissolution of Ca oxalate crystals, with dissolution increasing with both solution molarity and ionic potential of cation extractant. In spike recovery tests using a low-Ca soil, we estimate that 1 M ammonium acetate extraction dissolved sufficient Ca oxalate to contribute an additional 52% to standard measurements of soil-exchangeable Ca. However, in a high-Ca soil, the amount of Ca oxalate spike that would dissolve in 1 M ammonium acetate extraction was difficult to detect against the large pool of exchangeable Ca. We conclude that Ca oxalate can contribute substantially to standard estimates of soil-exchangeable Ca in acid forest soils with low soil-exchangeable Ca. Consequently, measures of exchangeable Ca are unlikely to fully resolve discrepancies in ecosystem Ca mass balance unless the contribution of Ca oxalate to exchangeable Ca is also assessed.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Contribution of calcium oxalate to soil-exchangeable calcium
Series title:
Soil Science
DOI:
10.1097/SS.0000000000000029
Volume
178
Issue:
12
Year Published:
2013
Language:
English
Publisher:
Lippincott Williams & Wilkins
Publisher location:
Baltimore, MD
Contributing office(s):
Forest and Rangeland Ecosystem Science Center
Description:
8 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
671
Last page:
678
Number of Pages:
8