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United States Department of Agriculture

Agricultural Research Service

Title: Soil Carbon Pools and Fluxes in Long-Term Corn Belt Agroecosystems

Authors
item Collins, Harold - SELF-EMPLOYED
item Elliott, Edward - COLORADO STATE UNIVERSITY
item Paustian, Keith - COLORADO STATE UNIVERSITY
item Bundy, Larry - UNIVERSITY OF WISCONSIN
item Dick, Warren - OHIO STATE UNIVERSITY
item Huggins, David
item Smucker, A - MICHIGAN STATE UNIVERSITY
item Paul, Eldor - MICHIGAN STATE UNIVERSITY

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1999
Publication Date: N/A

Interpretive Summary: The dynamics of soil organic carbon (SOC) play an important role in long- term agricultural productivity and the global C cycle. We used laboratory techniques to determine the dynamics of SOC in US Corn Belt soils derived from both forest and prairie vegetation. Measurement of the natural abundance of C-13 made it possible to follow the influence of continuous corn on SOC accumulation. The active pool (Ca) comprised 3 to 8% of the SOC with an average field mean residence time (MRT) of 100 d. The slow pools (Cs) comprised 50% of SOC in the surface and up to 65% in subsoils. They had field MRTs from 12-28 y for C-4 derived carbon and 40-80 y for C- 3 derived carbon depending on soil type and location. No-till management increased the MRT of the C-3 derived carbon by 10-15 y above conventional tillage. The resistant pool (Cr) decreased from an average of 50% at the surface to 30% at depth. The SOC dynamics were dependent on soil heritage (prairie vs. forest), texture, cultivation and parent material, decomposition characteristics.

Technical Abstract: The dynamics of soil organic carbon (SOC) play an important role in long- term ecosystem productivity and the global C cycle. We used extended laboratory incubation and acid hydrolysis to analytically determine SOC pool sizes and fluxes in US Corn Belt soils derived from both forest and prairie vegetation. Measurement of the natural abundance of C-13 made it possible to follow the influence of continuous corn on SOC accumulation. The active pool (Ca) comprised 3 to 8% of the SOC with an average field mean residence time of 100 d. The slow pools (Cs) comprised 50% of SOC in the surface and up to 65% in subsoils. They had field MRTs from 12-28 y for C-4 derived carbon and 40-80 y for C-3 derived carbon depending on soil type and location. No-till management increased the MRT of the C-3 derived carbon by 10-15 y above conventional tillage. The resistant pool (Cr) decreased from an average of 50% at the surface to 30% at depth. The isotopic composition of SOC mineralized during the early stages of incubation reflected accumulations of labile C from the incorporation of corn residues. The CO2 released later reflected C-13 characteristics of the C-4 pool. The C-13 of the CO2 did not equal that of the whole soil until after 1000 d of incubation. The SOC dynamics determined by acid hydrolysis, incubation and C-13 content were dependent on soil heritage (prairie vs. forest), texture, cultivation and parent material, decomposition characteristics. Two independent methods of determining C-3 pool sizes derived from C-3 vegetation gave highly correlated values.

Last Modified: 9/2/2014