Pedogenic carbonates in a calciaquoll associated with a recharge wetland
Knuteson, J.A. | Richardson, J.L. | Patterson, D.D. | Prunty, L.
Calcic horizon formation was studied in an Aeric Calciaquoll (Bearden series) adjacent to an occasionally ponded Typic Argiaquoll (Lindaas series) on the Lake Agassiz Plain of eastern North Dakota. Carbonates in the Calciaquoll accumulated from groundwater additions. Soil water monitoring during a year with near-normal rainfall and temperatures showed that an upward soil water flux existed during a 13-wk period from late spring through midsummer. Unsaturated hydraulic conductivity (UHC) values indicated that the 2BC horizon controlled upward water flux in this soil. Upward water movement through this horizon during the 14-wk period was estimated to be 36 mm. In late summer, evapotranspirative demand far exceeded the UHC of the horizon. As the soil dried, UHC values were further reduced. Assuming time of soil formation of 4000 to 9000 yr and detrital carbonate mineral levels of 10 to 15% by weight, annual additions of calcium carbonate equivalent (CCE) to the calcic horizon range from 0.1 to 0.2 mol m-2 yr-1 in this soil based on the amount of carbonate in the calcic horizon. Annual average levels of CCE in rising groundwater must be between 2.6 and 8.2 mmol kg-1 for the observed amount of carbonate to accumulate. The current amount of CCE in calcic horizon soil solution, as estimated by mathematically concentrating saturation past soluble ions to the observed constant water content, was 3.5 mmol kg-1, a value within the range estimated.
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