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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT TECHNOLOGIES FOR ARID RANGELANDS

Location: Range Management Research

Title: Soil carbonates and soil water

Author
item Duniway, Michael

Submitted to: Encyclopedia of Soil Science
Publication Type: Book / Chapter
Publication Acceptance Date: January 7, 2011
Publication Date: N/A

Interpretive Summary: High carbonate soil horizons are common in arid, semi-arid, and sub-humid regions around the world and have long been recognized for their importance in soil nutrient availability and soil structure. The presence of soil carbonates occurring as solidified masses or dispersed particles, however, can alter soil water dynamics from what would be expected based on non-carbonate soil properties. Understanding soil AWHC and dynamics is of particular importance in these dry climates. Soil carbonates in the fine earth size fraction are predominately derived from precipitates and are usually of the clay and silt size classes. Carbonate coarse fragments can be derived from carbonate parent material detritus or from pedogenic sources such as nodules and petrocalcic rubble. Parts of the profile can be continuously indurated with carbonates either due to high carbonate bedrock or the formation of a petrocalcic horizon. The accumulation of dispersed soil carbonates appears to increase available water holding capacity (AWHC) in coarse textured soils and some fine textured soils. Due to the relatively high AWHC carbonate rock-like material (0.03 to 0.22 m3 m-3), soil profile AWHC will likely be underestimated if fragments of indurated carbonate material or clastic of carbonate parent material are ignored. The high water holding capacity of petrocalcic horizons and high carbonate bedrock and the presence of water within these cemented soil horizons indicate their potential importance as a plant-water source, especially during dry periods.

Technical Abstract: The presence of soil carbonates occurring as solidified masses or dispersed particles can alter soil water dynamics from what would be expected based on non-carbonate soil properties. Carbonate minerals in the soil can be derived from high carbonate parent material, additions in the form of carbonate mineral containing rain or dust, high carbonate groundwater, and formed in situ as secondary minerals. Soil carbonates in the fine earth size fraction are predominately derived from precipitates and are usually of the clay and silt size classes. Carbonate coarse fragments can be derived from carbonate parent material detritus or from pedogenic sources such as nodules and petrocalcic rubble. Parts of the profile can be continuously indurated with carbonates either due to high carbonate bedrock or the formation of a petrocalcic horizon. The accumulation of dispersed soil carbonates appears to increase available water holding capacity (AWHC) in coarse textured soils and some fine textured soils. Due to the relatively high AWHC carbonate rock-like material (0.03 to 0.22 m3 m-3), soil profile AWHC will likely be underestimated if fragments of indurated carbonate material or clastic of carbonate parent material are ignored. The high water holding capacity of petrocalcic horizons and high carbonate bedrock and the presence of water within these cemented soil horizons indicate their potential importance as a plant-water source, especially during dry periods.

Last Modified: 7/22/2014
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