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Manganese oxidation and reduction in soils: effects of temperature, water potential, pH and their interactions

Citation

Sparrow, LA and Uren, NC, Manganese oxidation and reduction in soils: effects of temperature, water potential, pH and their interactions, Soil Research, 52, (5) pp. 483-494. ISSN 1838-675X (2014) [Refereed Article]

Copyright Statement

Journal compilation copyright 2014 CSIRO

DOI: doi:10.1071/SR13159

Abstract

Manganese (Mn) toxicity is a potential limitation to plant growth on acidic and poorly drained soils. Five laboratory experiments using such soils were conducted to examine the influence of soil temperature, pH and water potential on the redox reactions of Mn and the potential for Mn toxicity. The microbial inhibitor sodium azide was used in some experiments to assess the role of microorganisms in these reactions. The reduction of Mn oxides (MnOx) during waterlogging was faster at 20C and 30C than at 10C or 4C. Sodium azide slowed the reduction of Mn oxides at 20C and 30C during waterlogging but had little effect at 4C and 10C, suggesting that microbial MnOx reduction during waterlogging was minimal at the lower temperatures. Re-oxidation of Mn2+ in soil drained after severe waterlogging was only observed in soil not treated with sodium azide, indicating that even when very high concentrations of Mn2+ were present, Mn2+ oxidation was still microbial. Prior liming of aerobic soil established lower starting concentrations of water-soluble plus exchangeable (WS+E) Mn2+ and slowed the reduction of Mn oxides during subsequent waterlogging. After drainage, rapid re-oxidation of Mn2+ was observed in all lime treatments but was fastest at the two highest lime rates. In the fourth and fifth experiments, interactions between temperature and water potential were observed. When waterlogged soils were drained to 5 and 10 kPa, re-oxidation of Mn2+ occurred at both 10C and 20C. At 1 kPa, there was no net change in WS+E Mn2+ at 10C, whereas at 20C, the concentration of WS+E Mn2+ increased, possibly due to the lower concentration of O2 in the soil water at the higher temperature. In the fifth experiment, at 4C and 10C there was little or no effect on Mn reactions of varying water potential from 1 to 1500 kPa, but at 20C and especially at 30C, both Mn2+ oxidation and Mn oxide reduction were slowed at 1500 kPa compared with the higher water potentials. Overall, the experiments show that a delicate balance between the microbial oxidation of Mn2+ and the reduction of Mn oxides can exist, and that it can be shifted by small changes in soil water potential along with changes in temperature and pH.

Item Details

Item Type:Refereed Article
Keywords:soil, manganese, redox, toxicity, chemical and microbial redox reactions, drainage, microbial inhibitor, waterlogging
Research Division:Environmental Sciences
Research Group:Soil Sciences
Research Field:Soil Sciences not elsewhere classified
Objective Division:Environment
Objective Group:Soils
Objective Field:Soils not elsewhere classified
Author:Sparrow, LA (Dr Leigh Sparrow)
ID Code:93105
Year Published:2014
Web of Science® Times Cited:13
Deposited By:Tasmanian Institute of Agriculture
Deposited On:2014-07-11
Last Modified:2015-02-16
Downloads:0

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